Case Cleanup. I removed the RF shield from the inside of both IIGS case top covers. I wiped down the RF shields, and then I washed the case tops with some 409 cleaner and a brush in the tub. The next day once the cases were dry, I reinstalled the RF shields into the case tops with some UV Resin to replace the plastic melted rivets that I had to cut away.
RF Shield Reinstalled with some UV Curing glue where the plastic rivets had been.
The RF shields rust easily and already have some rust on them, so I didn’t want water all over them that I couldn’t readily dry off quickly.
For the working keyboard, I removed all of the keys that don’t have stabilizer bars. I then brushed out all the dirt, hair and dust from the keyboard. I then used the air compressor to blow out what was remaining. It didn’t look like anything had been spilled in it, so it cleaned up well. I don’t know how the stabilizers remove, so I didn’t want to risk removing them. I cleaned the keyboard with Windex and IPA as well as the remaining keys. I took all the loose keys and put them in the tub, spraying them down with 409 and a brush again brushing all 4 sides and the top. Then I rinsed them off well, and laid them out on a towel to finish drying. The next day they were dry so I used the other keyboard as an example to be sure I had all the keys reinstalled properly on the keyboard.
The cords including power cord were wiped down with Windex to get the worst of the dirt off, and a bit of touch up with some 99% IPA.
For the Color and Monochrome monitors, I opened both up to check them internally. I was checking for RIFA caps, which neither had. I was also checking if there were any problems that could be seen. There were no obvious broken solder points or evidence of leaking capacitors. Unfortunately the Color Monitor’s flyback case is cracking around the Focus control. I wiped out a bit of dirt and dust. There wasn’t anything else that I saw of any concern in the monitors. I also cleaned the case backs with 409 in the tub, and dried them out. The front of the monitors, I just cleaned with windex and paper towels.
The next day I was able to check the Monochrome display, I was waiting to ensure no water was in the monitor and that it was all closed up. The display worked normally. I don’t know if it is dim or anything. It looks fine to me, but I don’t use CRT displays often and my memory from when I was using Apple IIs in school has been way to long ago to be helpful. Internally the Monochrome monitor looked like it may not have been heavily used.
Testing the Monochrome Monitor with an original disk.
I now have a single IIGS in working condition with a 5.25″ Disk drive and Monochrome monitor.
It looks pretty good, but with the texture of the plastic, it still has dirt in the texture. I think there is a chance that simple dishsoap and a good scrubber would get some more of that out. That is what I usually use, but this had mouse filth all over it. I have seen people use Mr Clean Magic Erasers for such things, but they are actually abrasive, so I want to limit their use, I may give it a try, but they are over 30 years old, so they aren’t expected to look brand new, by me at least. I figured as bad as it was the 409 would do well, but it really was not as effective as I was hoping. There is some yellowing, and the old id number badge left a non yellowed spot above the logo that stands out a bit.
I do have the Color RGB Monitor cleaned up, but I have to make up a cable for it. Making cables takes time, and I’ve been working on some other projects. It is missing the back feet as well, so I will 3d print some new ones in TPU. It is also missing 1 of the “front feet”, which are a bit weird, and because of the front bar that tilts the monitor up it doesn’t rest on the front feet. The Monochrome monitor has what looks to be the same foot setup, so I figure if I can use them to measure up to quickly model replacement feet.
I also have the second keyboard to tear down and clean. That keyboard also has a few keys not moving properly, I don’t know what that might involve to correct. I have the other two 5.25″ disk drives to tear down and clean and service internally. I don’t need those two drives at this time, and I have cleaned the cables and outside of the cases.
The work on these items is mostly cleaning, and testing the items. The Power Supply did need some work, and the second keyboard has issues. The other Power Supply I am not going to be doing anything with at this time as I don’t need both IIGSs.
I ended up with 2 Apple IIGS computers. They were nearly complete. They were dirty, a lot of evidence of mice or more.
I did a basic wipe down of everything to get some of the nasty stuff of of everything before loading them up to bring them home.
On inspection at home, overall I had 2 Apple IIGS computers, with keyboards and the cables but the one keyboard has keys that are stuck and some damage. I also have 3 5.25″ disk drives, a Color Monitor (minus the cable), and a Monochrome Monitor.
I will be making various posts going over the equipment.
The primary thing was to check out the IIGS computers. I needed to see if either was working or reasonable to repair.
I focused on the first IIGS. First I cleaned it a bit better as it was still not very clean. I had checked both IIGS internally for leaking batteries, and thankfully neither battery had leaked, they were dated 1992. On seeing that they were in battery holders I was able to look up that these are the later ROM3 version boards with ROM3 and the additional ram. I removed both batteries, and gave the boards a visual inspection, they looked fine, a bit of dirt and dust.
From there I went to the power supplies. I opened the first one, it is apparently an ASTEC model. The visual inspection of the top looked pretty good overall, although the RIFA cap has some cracking. Nothing scorched or bulging etc otherwise initially.
On removing the PCB from the case to get to the RIFA cap, I found a surprise on the bottom. Under the Large Filter cap (C4), was a leaky black mess. Over toward the nearby C5 there was a mess and the solder mask and solder points looked bad nearby.
I first cleaned up the muck with some IPA while I was preheating my desoldering gun.
I pulled C4 and C5. The large C4 had no marks under it, it didn’t appear to have leaked. C5 though showed evidence of leaking. I take it leaked and migrated across the board, possibly through that large hole or somehow it managed to leak through the board some other way. There is a small pin hole under C4, but there was nothing on the top side, though the hole was plugged up with the gunk. The solder was quite contaminated around a good number of those solder points, and was a bit difficult to remove that old solder from those corroded points. I then had to use the fiberglass brush to remove some of the solder mask where it was damaged and the traces were corroding.
I used my MESR-100 ESR Meter to check C4 and C5. I also checked their capacitance. The large C4 330UF 200V capacitor had the proper Capacitance reading and a good ESR Reading as well. I reinstalled it. With C5, I was surprised to find the capacitance on it was still in spec for a 220UF capacitor, but the ESR was way to high. I’m fairly certain it was where the leakage came from as well, unless it was something that somehow ended up falling into the power supply. I replaced 220UF capacitor with a new one I had in stock. The board isn’t beautiful, but it cleaned up fairly well, everything was superficial. I removed the RIFA, and as I don’t have any spares in stock, I am just going to use it without one to do the testing and get one on order. I removed one of the resistors that had corrosion on the legs, and cleaned it up a bit before soldering it back in.
Above, it how the pcb looked after cleaning up the old solder and resoldering everything. The 3 now vacant holes in the upper left are the holes for the RIFA cap.
I tested the power supply output, and the +5V, -5V, +12V, and -12V all looked good. The +5V was right on, the others had a little variation being a bit low.
The other power supply is a Dyna Corp model. It has 4 RIFAs in it. It also has heat discoloration on the PCB.
I decided I wasn’t going to remove the 4 RIFAs, and that with the state of the PCB (and that I don’t “need” 2 working IIGS computers at this time), that I was going to just close this Power Supply up and not use it.
Now that I had one power supply working, I decided to test both mainboards with it. Since I didn’t know the condition of either monitor and I don’t have the RGB Cable, I used my bench LCD monitor with Composite video. Both mainboards powered up and showed the expected display.
I moved on to one of the Disk Drives. I just picked one of the three drives to do a cleanup and service it. I cleaned the case and cable with Windex and paper towels. I then took it apart. It was a bit awkward to get the drive out of the shell with how the front faceplate locks into the top and bottom halves. I then had to remove the top metal plate, and then the PCB and insulator and other plate below it. From there it was dusty inside, but looked fine otherwise.
I cleaned it internally with qtips and IPA. I cleaned as much of the dust from inside, as well as the rails. I also cleaned the print head with a fresh qtip and 99% IPA. I then put in new Silicone Grease on the rails and worked them a bit to make sure it was distributed well.
Just before putting everything back together, I saw something in the bottom of the drive.
Thankfully I found that and removed it before powering it on. Old gum wrappers some fool stuffed into the drive slot. With one of the drives, I wasn’t able to fully insert a disk into it before loading them up to bring them home, by the time I got home with them, I was able to insert the disk fully. I expect that was this drive, and that had moved out of the way.
I was still testing the IIGS, so I decided to test the Disk Drive before putting it back in the case.
The drive worked properly. I wasn’t making any unexpected sounds, and read the first disk just fine. I had 3 disks, and I tried the other two, and one of them worked. The last disk did not work properly, it would partially read but get to a point that it said to insert the proper disk.
That little Eyoyo monitor does a great job with Composite. It is very forgiving, and I expect when using any of my other monitors on Composite video won’t look as good.
Unfortunately Oregon Trail is not one of the disks, so that means I will have to get solution to let me play it on one of these machines. There are some other programs I would like to try out as well. I have more cleanup to do, the IIGS cases are a mess as well as everything else yet. One of the IIGS cases must be brittle, the lower frame as the one catch that holds the top was already broken when I got it, and then the second one broke when I opened it.
I finished cleaning the Disk Drive’s case and reinstalled it. I also cleaned up the intact keyboard just enough to use it, and it seemed to be working fine. I didn’t test all of the keys.
I found out these will not pass their self diagnostic without a good battery. I need a battery, and replacement for the RIFA cap. I also have to properly clean all the other parts including the IIGS cases.
When I purchased the TI 99/4a Computer a few years ago, the keyboard was not working properly. I had ended up with one of the Mitsumi based keyboards with the membrane that degrades. After taking it apart to separate the stuck membrane on the keyboard, it still wouldn’t work properly. The best option for me at the time was to get another TI 99/4a that had one of the other keyboard types in it as many of these Mitsumi membranes have failed.
There were other modern replacement keyboards for 80s era (well late 70s for the TI 99) computers, but there wasn’t one for the TI 99 that I had been able to find at the time. I looked over the Mitsumi keyboard, it is very similar to the Commodore 64 Mitsumi keyboard in construction. The plungers look to be identical to the Commodore 64 except they are white plastic instead of black. The “pads” on the bottom of the plungers are different though, as these work with the Membrane not with carbon pads like on the Commodore 64. The frame is the same style, and I expect it is possible the springs are the same or close enough to use. The Spacebar spring is not the same as the rest. There were projects for the Commodore 64, so it needed a PCB design, and maybe adapting the key “adapters” that were used for the C65. That was well beyond my current abilities (and probably still is).
I decided to buy another TI 99/4a with one of the “other types” of keyboards. I ended up with a TI 99/4a with a Hi-Tek brand Stackpole keyboard. The Stackpole uses square tubes that the keys insert into that tend to split at the corners. I do have some split tubes in my keyboard, but it was working fine. I did have concerns the stems would split worse with use. Shelby of the Tech Tangents (at the time still called AkBKukU) on Youtube worked on restoring another Stackpole type keyboard and released a 3d model to print new tubes for the keyboard. I printed one on my 3d printer and it turned out great. So there are options to extend the life of the Hi-Tek Stackpole keyboard. The keys may not work as good as new, but they should be reasonable.
With the keyboard issue sorted, I shelved the idea of coming up with a new Keyboard PCB. I didn’t like I had an otherwise completely functional TI 99/4a sitting unusable on the shelf though.
I recently came across a project to rebuild the Mitsumi 99 keyboard with Cherry MX Style mechanical key switches. https://github.com/visrealm/keyboard4a99 I watched the Youtube build guide. I have worked on various keyboards, and the project is quite strait forward. It is designed specifically to rebuild the TI 99/4a Mitsumi keyboard, which is what I needed. It reuses the keycaps, the spacebar supports and clips, as well as the keyboard cable and some support rails and screws.
I expect with a bit of work, that it could be adaptable to use the Hi-Tek/Stackpole keycaps. It would take a different Stackpole to Cherry MX Key Adapter (I found one, but I don’t know that key height would be correct https://www.thingiverse.com/thing:4735119) You would also require making some metal support rails. I believe the keyboard “cable” is shorter on the Hi-Tek, so you would probably be making a new one. The visrealm project has an alternate spacebar support clip, which may work with it, depending how the spacebar works.
He has the Bill of Materials in the Github post. As of right now.
We need the original Mitsumi type keyboard to get the Keycaps, and Metal support rails with screws. Then optionally the keyboard cable (which I used), and the Spacebar Clips to put into his inserts. There is an optional version of replacement Spacebar Clips, but there is no point in me leaving those on the old keyboard, the same with the cable it can be recreated but there is no point in that for me.
My bad Mitsumi Keyboard
Then we need the Keyboard PCB. I downloaded the Gerbers from Github and uploaded them to JLCPCB. He recommends black to reduce seeing the PCB through any gaps between the keys, so I went with black.
5 new PCBs
We need 47 Cherry MX Compatible switches. I wanted Brown Switches, as they are my preferred type. I know there are now many other “colors”, but I don’t know anything about the colors other than red, blue and brown. I like a reasonably quiet switch, and I like the tactile feedback of the brown switches. I went with the cheapest option for me to get enough brown switches, which was to buy one of those 60% keyboards for $20. It was cheaper to buy that keyboard on sale than it was to buy 50 loose key switches.. I was sure to buy a keyboard with removable switches. It was a bit of a pity to strip the keyboard. It seems to be made well enough, but I don’t like the form factor. I will keep it for the few remaining switches, or incase one of my kids wants a keyboard of that style. It will be easy to repopulate it.
Parts Keyboard for Switches..I now have enough loose key switches.
I needed a 8mm latching switch (compatible with the GPBX-800L at Mouser) for the Alpha lock, which again I went to Amazon, as I don’t have a need to place an order with Mouser. I now have 19 spares, and 20 of some three other variants. There is also a 1N4148 diode for the Alpha lock mod to keep the Alpha lock from letting the joysticks work. Which I have plenty of in my stock.
I used some M3 Brass inserts. It mentioned 10, where there are 3 for each of the “PCB mount rails”. I take it the other 4 are for the Spacebar support mount, but the ones to reuse the Mitsumi spacebar clips do not have the larger holes to accept the Brass inserts. I used M3x8 machine screws, for in the Brass Inserts as well as for the Spacebar mounts. The holes for the Spacebar mounts are for self-tapping screws, but the M3 machine screws went in fine, and actually were nearly too tight.
We need to 3d print the PCB mounts for each side, the Alpha lock, the PCB support backers (2), the Spacebar supports (2). The Keycap adapters (46?), there is a model that you can print them all at once, I did find them annoying to get apart but they were usable. There is also a unique Keycap adapter for the Spacebar (supposed to be a little different), and a unique one for the Right shift. I printed the parts all in PETG. I did make sure they were not brittle, during assembly and testing I had no issues with any breaking in my case. I did print “outer walls” first, this kept the cross on the top sized properly and kept it from stringing between the crosses.
The various 3d printed parts.
I have to have the Mitsumi keyboard pulled from the TI 99. Which is 7 screws in the bottom to open the case. Then 2 to release the power supply board, 3 to release the main computer pcb and housing, and 4 screws to remove the keyboard itself after unplugging it from the computer pcb. The guide on Github shows all the screws and steps.
Next I striped down the Mitsumi keyboard. Desoldered the wires from the Key lock switch. Then I unscrewed the metal support rails putting them to the side to reuse later.
Starting here. First I will remove the metal rails to reuse. Then the remaining screws.
Then I took the rest of the screws out to release the PCB. Next I used my desoldering iron to remove the keyboard cable. Just a little note on the cable, “pin 1” is Not the Red side of the cable. Keep an eye on how it is installed and reinstall it in the direction it was on the original pcb.
Cable to be desoldered.
While the PCB was off, I removed the spacebar and took out the Spacebar support clips.
Spacebar, Spacebar clips, and Keyboard cable. (and 8 key)
While I had the Mitsumi keyboard in storage, I had broken the 8 key stem. I had to get the broken stem top out of the 8 key without damaging the key. I used a 1/16th” drill bit to drill a hole in the broken stem top. Then I screwed a small screw into the 1/16th” hole, and used a pair of pliers to carefully pull the part out of the keycap. The screw was only screwed in a short distance, if it is too big, or in to far, you may wedge the part in tighter.
Getting the broken stem top out of the 8 key
I then took the screw out and used some super glue to glue the key stem back together, it may or may not hold up, but I also don’t expect the keyboard to get keycaps again.. After that I screwed the old keyboard back together. I will keep it for parts. If you don’t put the PCB back on, when the keycaps are pulled off the key stems will just fall out everywhere.
Stripped Mitsumi, and springs.
To start building up the new keyboard. I mostly followed the video guide. First I took the Metal support rails and added Kapton Tape to the bottom for insulation. The guide he used clear tape, and suggests maybe 2 layers. The Kapton Tape is much more durable, and is a proper insulation tape it you happen to have it. Note that the rails are “turned” compared to on the Mitsumi, using the “other holes”. I lined them up with the white lines on the PCB Silkscreen.
Kapton Tape for Insulation.
Once the rails are insulated they get installed with the 6 original screws, into the 3d printed support rails that are basically just to hold the screws.
Then I installed the Spacebar Supports. You can also see the PCB Mounts with their brass inserts installed. I was checking that they were going to fit properly. The PCB Mounts were added after all the key switches were soldered in.
I soldered on the keyboard cable next.
I started soldering in the switches. It is recommended on Github to get the key switches with the extra support pins in line with the center posts. The switches I purchased did not have those. It did make soldering them in strait a bit more difficult. I did work to solder them in strait as possible, which I did have some issues with. If they are perfectly strait, well the keycaps will still be crooked… well in my case they were. While I don’t know the reason for them being crooked, once installed, it has something to do with the 3d printed adapters.
To solder the switches, I started with the spacebar and went across the rows from there. I didn’t do it the way the guide showed. I am sure they would have been very crooked, maybe if I my switches had the additional alignment pins it would have been too bad. I ended up using Silly Putty to keep the keycaps in place and strait when I flipped the keyboard. With just one Silly Putty egg, I could do a full row. Though when I started I was using larger clumps of it as seen in the photo below.
The 0 key switch ran into the edge of the one 3d printed screw rail. I had to shave just a tiny bit off the rail to get it in strait.
A Tiny Shave0 swtich fits after the Shave.
So now the soldering is completed.
The soldered keyboard. The Spacebar Clips are installed. Tested the 8 Key.
So we did the key adapters. I printed out the grouped file. Then I had to cut them apart. I used Cura which did something weird to the one layer. Cura was reliable, but Orca indicated a better outcome, but I couldn’t get it to print successfully.. So It came down to using a new sharp Xacto blade to cut the adapters apart. When I had rough edges, I cleaned them up with the side cutters or Xacto blade.
The spacebar has a slightly different adapter. The Alpha Lock has a different type of cap. Then the Right Shift has a special centering double pin adapter.
So then I went through all of the keys separating the adapters and installing them. The key switches are quite strait, although not perfect. Though once installing the keycaps with the adapters they end up not aligned very well. They look to have printed well. I expect it is due to variations in the inside stem that goes into the Cherry MX type switches. The seam on the outside may have also affected them and made them rotate a bit. The stems are rectangular, so you have to be careful to not have them rotated 90 degrees, as they may “force on” but will bind. They may have been more consistent if I had been careful to not rotate them 180 degrees, but that was hard to tell.
Below is the completed unit ready to be installed. If you click on the front view, you can possibly see the P key is obviously twisted. The angle makes it hard to tell how numerous of the keys are twisted a bit.
Next I installed the keyboard. The keyboard is the lowest part of the 99 or rather the highest part. The keyboard must be installed before the Computer PCB and under the Power supply PCB. First I lifted the loose computer out of the way just enough to drop in the keyboard behind it, so that I could get the keyboard screws in properly. Then I lifted the computer up to plugged in the keyboard to the computer assembly. Then I screwed the computer and finally the power supply PCB. After that the bottom gets screwed back on. Finally the outer part of the Power Switch piece slides back into the case.
Finally the TI 99/4a has the new Cherry MX style replacement keyboard installed.
The P is kind of obvious from the angle again. There are other keys twisted a bit. I tested the keyboard before reassembly of the computer. All the keys work as expected including the Alpha Lock. The only issue, is the Enter key must have a clearance issue, it is partially press. I may pull the 99 apart to recheck it. It is only partially pressed, so it isn’t stuck down, and it still operate normally except not raising fully to the expected position.
As far as the project, it is great. The oddity is with the 3d printed key adapters. Others may have less problems with that and not have keys twisted noticeably. The key switches with the extra alignment pins may be a good idea and speed up assembly. The Alpha Lock switch doesn’t have “much” travel, it is not very obvious that it is pressed by looking at it. It does work fine.
I did have an issue with the Spacebar initially not wanting to raise up, it was binding a bit. I loosened the 3d printed supports and managed to get the alignment better. This may also be due to “twisting” related to how my adapters printed.
The keyboard feels great to type on. I was able to put the Hi-Tek Stackpole type keyboard back in my spare TI 99/4a making it complete again.
I hope to make some time to use the TI 99/4a. I think I’ll put away the Commodore 128 for a while so I can have the 99 hooked up and see if I can get familiar with it.
When buying the parts for the Jedimatt 32k build, I purchased a new SRAM IC for the Backbit 32k unit. I replaced the ram IC on the Backbit 32k unit and it still wouldn’t work, reliably. That indicates some other fault on it, either the CPLD or somehow the Edge Connector on it not making proper connection. It will “randomly” work for a short time then quit again.
The Static Ram I purchased for the Jedimatt 32k unit uses a Low Power CMOS 28pin 256-Kbit 32k x 8 Static RAM that is TTL Compatible that runs at 2.7V to 5.5V. The Backbit 32k unit uses a CMOS 28pin 256-Kbit 32k x 8 Static RAM that is TTL Compatible that runs at 4.5V to 5.5V.
I looked at the Datasheets for the two of the Static RAM ics. With one being branded Alliance Memory and the other Cypress, although both list Alliance Memory Inc as the manufacturer. I looked over the pinouts, and they are pin compatible, short of the Address inputs are numbered differently. The primary difference is the footprint. The AS6C62256-55PCN that I purchased for the Jedimatt 32k build is a 28PIN 0.6″/15.24mm Width DIP Package. The CY62256NLL-55SNXIT that is on the Backbit 32k is a 28PIN 0.295″/7.5mm Width SOIC Package.
I purchased some SSOIC to DIP Adapter PCBs. I had assumed they would be sized to adapt to the 28PIN 0.6″/15.25mm Width. I was wrong, they are wider. They are also the narrower SOIC Footprint, which happens to be the same footprint on the Backbit 32k PCB. That meant the CY62256NLL already had the legs bent to go on the narrower footprint, which by the way, is no fun doing. I guess it would have been to easy to just solder the CY62256NLL-55SNXIT to the Adapter and put on the Round Pin headers.
I started with soldering the CY62256NLL-55SNXIT to the Adapter PCB. I then installed a row of Round Pin Headers in Pins 15-28. This is because of where it needs to fit on the Jedimatt 32k PCB. I next need to install a row of offset Round Pin for Pins 1-14.
I went back to the same Round Turn Pin Sockets that I had used on the Jedimatt 32k Edge Connector. I installed the Round Turn Pin Socket row into a Round 28Pin IC Socket. This is why I used the Round 28Pin IC Socket instead of the standard dual wipe 28Pin IC socket that I specified in the parts list for that build. I then inserted the adapter board above to find the spacing I needed to get everything aligned.
Once I had it held in the spare 28Pin Round Pin IC Socket, I took some Solid Copper Wire (a strand from some Cat 6 Solid Core Copper Network Cable) and stripped the insulation from it. I shaped it to fit into the Round Pin Socket. I made up a total of 14 pieces.
Copper WireAll wires inserted. They can flop around though.
Above you see the little copper wires as fitted into the Round Pin Header. I then placed the PCB onto the wires to Hold them in proper alignment. Once they were held in place, I soldered them into the Round Pin Header Socket.
Aligning the pins while solderingAfter SolderingAnother angle
Once the copper wires were soldered, I installed the Adapter PCB into the spare IC Socket and soldered the wires into the PCB to get the proper alignment for everything.
Installed to SolderAfter soldering and trimmingI was sure to fill the holes.
With it upside down, I then made sure to have good soldering on the bottom to help the Copper Wires keep secure. The bottom of the PCB had Kapton Tape on it to keep the Copper wires from wearing into the solder mask and shorting over time. Now the adapter board is all soldered up. It was time to see if it will fit.
Time to pull the Socket.Here you see the Kapton tapeIt is a close match.
Below you can see it installed into the PCB. I guess now the Green PCB is fine as they look good together.
It is just barely up over the case. The Top Cover has a hollow in it though so it will still fit.I think it looks great.
It was time to power it up and see if it works.
It seems to be stable and working properly. I am going to leave this CY62256NLL-55SNXIT on the adapter PCB installed into my Jedimatt 32k Memory Sidecar. I will put the 28PIN DIP Static Ram IC back in my spare parts. I have 4 more Jedimatt 32k PCBs that I could build up. I may still try to revive the Backbit 32k Memory Sidecar, but if I don’t, I could at least salvage the other CY62256NLL-55SNXIT and the Edge Connector to build another of the Jedimatt PCBs.
8/31/25 A little update on the Backbit 32k Memory Sidecar. I did buy a new CPLD for it a while ago, but before installing it, I decided to strip down the whole board. I removed the 5 Caps, the Edge Connector, the ram and the cpld. I cleaned the pcb. I reinstalled the Edge Connector flipped 180 degrees, I felt it potentially was a contact issue, and flipping the connector may make a difference. With the edge connector “pins” being flush with back holes on the pcb, it may have had a bad solder joint in one of the pins where the solder didn’t flow properly to the pin? I then soldered the Ram IC, CPLD and finally the capacitors back on. With practice I have been doing much better with soldering the CPLD. Also with good flux, and a new microscope for inspection. The primary issue with the board was solder bridges, some very small bridges kept hiding between the CPLD pins, but the new microscope made them much easier to see. After cleaning and reinspecting the pcb, it is working in the TI 99/4a just fine. I tested a couple 32k programs and they started fine, I have been running Jedimatt’s Expansion Memory Test Burnin as seen above for over 20 passes on it. I’m glad it is finally working reliably. This does mean I now have two 32k sidecars, for now I think I’ll use the Backbit one. I also have a spare CPLD, the primary reason I reinstalled the original one is I really don’t know how to program the new one, as to if I can use the same method I have used for the ZX Nuvo 128 board, or if I would need a different programmer. The board also does not have any traces going from the JTAG pins, meaning soldering on very small wires to very small pins to even attempt it. There may have been a bad solder connection or bridge, or it may be the edge connector in some way. I did find that the Andonstar 246S is a great upgrade over the little lcd microscope I had previously. It is much clearer and I could see the solder points and solder bridges that needed to be cleared. It has enough clearance to the microscope that I can use it to view the screen while soldering.
I have had the TI 99/4a for awhile now, and posted the Recapping of it. I actually have two TI 99/4a computers as the first one had a bad membrane type keyboard. The second one had a Stackpole type keyboard, which is is working order (although some of the square tubes are split). The Joysticks are awful, and I built up a Joystick Adapter to plug in Atari 2600 compatible joysticks to it. That made things much better for it. I also built up a Pitfall Cartridge for it and 3d printed a shell. Still I haven’t used it much. The Ti 99/4a was the first computer I had, it was old at the time. I had a few cartridges for it, and used BASIC in it at the time. It was quite limited with all the more software I had available.
In anticipation of getting a FinalGROM Cartridge or Backbit or something, I had purchased a 32k Memory Expansion that was for sale from Backbit. After I received it, I designed a 3d printed case for it. It turned out really well and has been sitting with my TI 99/4a since then, but I was unable to use it at the time.
I like the small and clean look of the Backbit 32k.
The FinalGROM Cartridge came in, I made up an SD Card for it. I tested it with some games that did not require the 32k Memory Expansion. Then I plugged in the 32k Memory Expansion and the 99 wouldn’t power up properly, it just made an audio buzz. I checked the contacts, checked the Memory Expansion. I noticed flux residue on the ICs of the 32k Memory board, and cleaned that off just incase it became contaminated. I ended up removing the CPLD from the board, and inspecting it. I soldered back on the CPLD, and the buzz was gone, and I got it working just one time. Then I powered it off and tried another 32k program and it quit working again. I rechecked the soldering on the CPLD, as well as the ram IC and edge connector and touched it all up. It would randomly work, it may pass Jedimatt’s Burning Ram test for a few passes then fail. Then it generally won’t detect the 32k memory until it is powered off a bit and reseated.
Backbit has quit selling the 32k Memory Expansion, and has released on Github as a project to allow you to build your own.
The Backbit 32k is more compact, and should be cheaper to make than Jedimatt’s design if you have all the required equipment to program and assemble it. Jedimatt’s 32k which is available to build by ordering PCBs with the provided Gerber files and standard components. Jedimatt’s 32k requires no programming of components. There are a few issues with building the Backbit 32k. It has a CPLD and that requires programming with a JTAG programmer. The board doesn’t have a JTAG Header. I believe this is simply due to it not being designed as a DIY Project, Backbit is a business and she makes and sells her products. I later found the RAM IC Footprint is wrong, at least for the ram IC that was fitted on mine when I bought it. The CPLD is on the top edge of my ability to solder with the super fine pin pitch. The Backbit 32k has not been around nearly as long as Jeditmatt’s, I can’t be sure that the problem is a defective part. It may also just not like my specific Ti 99/4 for some reason.
Jeditmatt’s 32k design has been around for many years. It is all through hole style components and easier to solder together. Surface mount soldering is not that difficult with some practice. That is at least for the larger parts, the smaller pin pitch like the CPLD gets far more difficult for me.
This left me with a problem. I know I can build Jedimatt’s design, I know it is thoroughly tested. It takes way more parts and time to assemble, and is also more expensive to build. I just love how the Backbit 32k looks. I also currently have no interest in a TIPI which does require Jedimatt’s type of expansion.
I looked around and found a Jedimatt type expansion for a reasonable price with shipping. I would rather build it though. I looked into it. I found all the required parts at Digikey. I also found the Ram and CPLD for the Backbit 32k there.. I also found a more “stylish” case for the Jedimatt 32k board on Thingiverse.
I decided to order the parts for Jedimatt’s board. While I was at it, I did order a replacement ram chip for the Backbit 32k board. I could have picked up the CPLD as well for $3.50 or something. I wasn’t interesting in trying to hand wire that for the JTAG programmer at this point (I may next time I place an order).
Jedimatt’s 32k Parts List. I have provided links for more specific parts. The most generic parts can be purchased easily. I included a link to the type of Round Female Socket Pins that I used, Digikey does have them as well if you are willing to look for them.
Jedimatt’s PCB Design. Download his Gerber files and order from your favorite PCB manufacturer.
I downloaded the Gerber files from Jedimatt’s site. Then I went over to JLCPCB and ordered the boards as that is where I order my PCBs from. I managed to order 5 of them and have them shipped to me for a total of $4.11 ($2.00 for the boards and $2.11 for shipping and taxes). I did kind of mess up, I didn’t want them in Green, but forgot to change it. The other colors did list they would take 2 more days to ship though.
I placed my order with Digikey for the parts I required. Between the PCBs and the Digikey order, I paid less than I would have for a completed 32k Memory Module on Ebay. I did have the 74HCT138 already, as well as the Resistors, Capacitors, 2.54mm Pin Headers, 2.54mm Jumper, DC Power jack, LED. I am also 3d printing the case. I ordered 5 of each of the 245s and 21s as well as two of the ram ics (and a replacement ram ic for the Backbit 32k incase that was the fault there).
First the Backbit 32k. I replaced the ram ic. The one I ordered was the exact part number that had been on it. I had the same results. Initially I couldn’t get it to work at all, once it made the buzz on power up, on removing it and trying it a few more times, it just failed every time I ran the RAM Test on it. It then worked for a little one time.. So it is on the shelf incase I want to buy another CPLD for it at some point.. I am wondering if it may be the edge connector is for some reason not making good contact. I am thinking I may get out the other TI 99/4a to see if it works on it. That one has no keyboard in it though, and I can’t start the ram test without one. The keyboard for it may be just working well enough to do that though if i reinstall it..
Next I moved on to the Jedimatt 32k build.
The boards came and looked great as usual.
The part that needed the most consideration was the Edge Connector. The edge connector that I purchased is of the same series as the one I purchased to replace the Cartridge Connector on my Commodore 128. Being that the connectors are the same 44pin, the difference between is the one for the Commodore 128 was a Right Angle connector. Being how it worked with the Commodore 128 I figured it should work for the TI 99/4a. It needed modification though, to remove the “mounting hole ears” on the side just like it had with the Commodore 128. This was a bigger deal here due to fitting in the 3d Printed case, the opening is very tight, and I needed to file it down a bit smaller than I thought I would.
There is a difference between the Edge connector between the Jedimatt and Backbit 32k. Jedimatt recommends some “individual pins” to use as extenders on the Edge Connector. It doesn’t seem they are available. I used Round Pin Female Socket strips. This is required because the “legs” of the Edge connectors are too short to reach deep enough into the side of the Ti 99/4a, or into the pass through socket of other Sidecars like the Speech Synthesizer.
I printed out the case and fitted the board to check how far the connector came out. With no pin headers in between it was way to short. I then tried with 1 pin header to see how that fit. It was still to short, compared to the Backbit 32k. The Backbit 32k didn’t use pin headers to extend the connector, it was cheated a bit by not putting the edge connector pins the whole way through through the PCB. The 3d printed case I made for the Backbit 32k is much thinner than the cases designed for the Jedimatt 32k (or at least the one I am using). I could rework the 3d printed case for the Jedimatt 32k, and maybe I could have managed then with a single pin header to extend it. That was not something I wanted to do though, it would have taken a good bit of work on the model.
That meant I needed to stack 2 of the Round Pin Female header pins for each of the 44pins of the edge connector. Which required stripping out 88 of the Round Pin Female header pins. The next step was to insert them into stacks of two each. The stacked pins were then soldered together, holding them with my Helping Hands. I went to stacking 5 pairs at a time and standing them up in holes in the PCB by the time I was done. While it was a bit awkward being they could spin around and even be picked up by the solder iron, that was quicker than trying to get the alligator clips in the Helping Hands to hold them properly.
The pin header strips before removing, then the individual pins, a pair of stacked pins and in the middle a pair soldered.Starting to put the pairs of pin headers on the connector.The connector installed.
That was a lot of time consuming work. Stripping the 88pins out of the strips without loosing or damaging them. Then stacking and soldering them together in pairs without making an awful mess of it. Then installing them onto the modified Edge connector that I had taken the wings/ears off and sanded down a bit more to fit through the 3d printed case.
To get the alignment correct, I fitted the pins and edge connector into the PCB. I then soldered the 4 corner pins into the PCB. I then aligned the edge connector and soldered the 4 corners of the edge connector to the pins. This let me align it all nicely, and after that it was easy soldering the rest of the now captive pins to the Edge Connector and PCB. Doing the soldering that way worked very well. It is very solid, it doesn’t look too bad overall once it was finished. I had tried to find what other people were using to extend the Edge Connector, it looked like one example was using the same Round Pin Sockets stacked up.
Above you can see the Jedimatt 32k Edge Connector does extend just a little bit higher than the Backbit 32k Edge Connector when they are in the cases. That was the closest I could get it with using the Round Pins to extend the Edge Connector. That does make it have a bit more gap between it and the Speech Synth Sidecar and or the TI 99/4a. I am thinking of that “heatsink looking” interface bit on the side of the Speech Synth Sidecar where it meets up to the TI 99/4a. I could make one of those and stick it on the Jedimatt 32k to support the gap in a very similar way.
The Backbit 32k has a serious time advantage due to not needing to extend the Edge Connector pins. You can see below the BackBit 32k just solders in the Edge Connector, keeping the pins as barely in as possible to extend it out as far as possible. You also see it has far less components overall. (Update 8/31/25 the Backbit 32k is working now, I striped it to be the bare board, flipped the edge connector 180 degrees and reinstalled the ics and capacitors, and with a new microscope I could inspect the work properly to clear any solder bridges and see that all the pins were soldered properly)
Backbit 32k
The rest of the Jedimatt 32k build is strait forward through hole soldering. Keep in mind that you have to install the Jumper for the Power Selection. To the front it uses the 5V from the Ti 99/4a Expansion port (requires a mod to the Speech Synth Sidecar to use), and toward the back of the TI 99/4a it uses the Power Jack and you need to connect up a 5V Power supply. Be sure to only use at 5V Power supply. I am using the Ti 99/4a to power it from the Edge connector with my modified Speech Synth Sidecar. Also install all the ICs on the board in the correct orientation, Pin 1 toward the Capacitor.
The case design intends the LED to tight to the board. There is a “clear” lens bit to print. I am not sure how that is fitted and decided to mount the LED pointing out through the hole.
As modeledImpacts the Screw here.Removed a bit so the screw fits.
I had taken the top out of that circle so the LED would clear, but on trying to close it still didn’t close. On pressing it a bit, and then opening the case, I saw that the screw in the corner hit that one spot around the LED housing. On removing a bit of the plastic there, the case then closed properly. I printed it in a Silver and Black theme to fit the TI 99/4a color scheme. The 4 screws are not specified, I used four 2mm by 10mm long screws and nuts (or 2.5mm, but I believe 2mm), a little shorter screw may have cleared the LED housing..
I connected it up and ran the Ram Burn in test on it. It passed all the tests for 12 cycles, then found an error on one of the banks. I powered it off and back on, and ran the test again, it was working again. I am not sure the issue, or if it was a random failure. I did do some more testing with it today, and it worked properly. I tried out a few 32k Games and Programs all of them ran fine.
The case printed reasonably well, but has room for improvement. The Silver is a sliver PLA, the 99 4 and A had little nearly “floating bits” that are missing. They were all partly there, but due to a defect on one and the poor strength of those bits, I removed them. I am thinking of possibly reprinting it as a 2 color print with a black insert filling in the letters to give it strength to retain the floating bits. I didn’t print the “inner blocking piece” You can see the PCB and parts inside through the openings. The back is printed in Black PETG, the case itself is a snap/friction fit top. The screws hold the PCB to the Bottom, but do not hold the “top” on.
Jedimatt 32kBackbit 32k
The Speech Synthesizer doesn’t pass 5V through it without a modification as shown on Jedimatt’s website. You can alternately use the external 5V Power Jack to power the 32k Memory expansion. If you have built either of the 32k Memory Expansion Sidecars, it should be no problem to add the wire to connect the 5V Pin in the Speech Synthesizer.
So this process turned out to be pointless and a waste of time and money for me. As for how to replace the cartridge port, it can be a fairly decent guide though if it was really needed.
Because I was having issues with Cartridges with my C128, even after cleaning I decided I would replace the cartridge port. In the end the problem was I made the C128 Diagnostic cartridge incorrectly. While the port was not 100% reliable, and actually the new one isn’t quite 100% with a certain game cartridge. I believe that is also the cartridge contacts fault and not the C128.
Anyways on to replacing the port. The first thing is finding a proper replacement part. Doing a search I could find replacement C64/C128 cartridge ports from some “retro online stores” in Europe, I couldn’t find any in the US. I wasn’t interested in paying the shipping and waiting on that. After finding some specifications listed I did more searching and found a close replacement at Digikey. The only difference seemed to be it had mounting holes in extended ears on the connector.
I took the chance and ordered it in, checking it fit the cartridges properly. It just needed a little modification which was easy with the rotary tool and a diamond cutting wheel.
The next part is getting the old port off.
To do that I used my vacuum desoldering gun. Of course I didn’t check that it had been cleaned, so it plugged up after the third solder joint. It took me far more time to tear it down and hand drill out the jammed bit of solder and get the bore cleaned out properly than to get the port desoldered after the fact. Always check your tools are in proper condition before starting to use them. The trick with the desoldering gun, it is very hot when I am done with it, so I put it back and forget about it usually..
It is very important to get the pins all free before trying to remove the port. I got every pin free before trying to remove it. Desoldered all the pins then check moving them each one at a time with small pliers. The reason this is extra important here is the “Glue” in the third picture. You have to pry it off, or I guess maybe get the board hot enough it melts somehow.. Without damaging the board. I preheated the board from the bottom with my hot air gun to about 200 degrees hoping to help loosen the connector. It was still very tight, and when it the glue let go it let go all at once popping the connector off. If I had a stuck leg, I likely would have torn traces from the board..
The new port was a good fit, I think it is just back a tiny bit from the original port, and the pin spacing between the rows might be off by a little, it is close though and fits fine. I put a little E6000 glue on to help hold the port. I could have cut the rest of the “ears” off fully. In testing cartridges, they seemed to come in contact with the ears, but be fully seated when doing so. I may at some point find some cartridge that doesn’t fit in deep enough due to that. The ones i have currently all look like they are seating nicely though.
After all that work, the C128 Diag cartridge still didn’t work properly. I made that cartridge awhile ago, and I pulled the documentation. I pulled up the EPROM Datasheet. It turned out that I set the jumpers for two of the pins to be pulled to Ground, I am not yet sure why, but it seems they weren’t actually pulled to ground. If they were the cartridge wouldn’t have worked at all. That is what threw me off all this time, it “sort of worked”, but kept crashing when I walked away. If I held the cartridge it would often work for awhile.. Those two pins on the EPROM needed to be pulled to 5V instead. Since they were not pulled to ground (for some yet unknown reason), and they were not pulled to 5V, they were just floating. This meant they might register as if they have 5V or they might register as if they are grounded. So the cartridge “might” work, or it more likely “wouldn’t work”. On fixing the solder bridges, so that it was actually putting those two pins to 5V, the cartridge works properly all the time.
For the EPROM I used, a 16k one, “A14” and “A15” don’t exist. They are two other signals related to if the EPROM is in Programming Mode or Read mode.. Because they were floating it would go from being readable or not being readable. If I used a larger EEPROM, I could have A14 even A15 as well, I didn’t need a larger EEPROM as I was only putting two 8k Diag Roms on the cartridge. Because I did that, I could use this miniature switch on it like you see on some other multi selection cartridges. If I had gone with a larger EEPROM I would have had to go with DIP Switch type switch for it. That is what the footprint there is for, or for standard 2.54mm spaced Jumper pins.
While it was a bit disappointing that this was a waste of time and money, I now know the C128 is fine. I am also keeping the original port as a spare. While I was at it, I made up customized case for the C128 Diag Cart modified to give me access to the switch and reset button as well as allow for the socketed EPROM. Normally you wouldn’t socket the EPROM so that it will fit properly inside a standard cartridge shell. I socketed the EPROM on this cartridge, as I have very little use for it, and figured I would not be keeping it. The case protects the cartridge and makes it easier to align when inserting it into the computer.
Above you can see the customized case. There is a switch extension (you can see some examples of the extensions beside the cartridge) to make that tiny little switch accessible on the case, and an extension for the reset button.
I purchased a RETRO.care MAXduino kit to build up for used with my ZX Nuvo 128 to use with .txz files. I found it was well packaged and the provided instructions were good. It is a quick and easy build. The kit came with all the required parts to do the assembly. I found a case on Printables to fit it. I printed up the case in white, but did a blue print in place inlay on the buttons. This case was a bit bland, so after building and testing, I made a few minor changes to the case and reprinted it.
It was a quick and easy build. Put the capacitors in the right place as there are 2 values, put the LED in in the correct direction. That is about it. The microcontroller ic was already programmed with the latest firmware. I guess I started putting it together before taking the pictures.
Everything is nicely labeled on the pcb design.
It didn’t take much time at all to assemble with so few parts. To get the pcb in the 3d printed case, I had to shorten the Reset button a bit. It seems someone managed to wedge the button in, I guess by putting the button stem through the hole and flexing the other side of the case out enough to get the audio jacks to fit in. I preferred to shorten the reset button, as I don’t want it to stick out too far and accidentally press it anyways. It is basically flush with the outside of the case, but easy enough to press when I want to.
After that it was down to plugging in the remaining parts and putting it into the case.
I tested it out and it worked great. I was able to load .tap and .tzx files without any issues on my Nuvo 128.
The case was a bit boring. I decided to make it a bit more colorful and fit the style of my Nuvo 128 a bit more.
To make the print in place inlays. I created an inlay model for each of the 4 colors in Tinkercad, plus the primary case model with the hollows in it. I make a skirt like ring around each set of models that I export with every part. I choose my first color to print, then once it is finished, I set the printer to maintain the bed temp, and swap and purge the filament for the next color. I have it print with zhop on, and the inlays are either 1 or 2 layers in height. I remove any skirt, and purge line, then print the next color model. Then repeat that process for each color. Finally I print the main model over top. You can see the Green line was kicked loose a bit, but it was good enough that it wasn’t worth starting over.
I made two other minor changes to the case. I created an angled fill in around the USB Port to close the hole up a bit. I also found that the back plate set deeper into the back of the case than I liked, so I shortened the lip a bit so that the back was more flush. It was minor, but I like it better that way.
This device is similar to a Tapduino for the Commodore 64, but is not compatible with it. I purchased it for use with the ZX Nuvo 128 for .tzx files, as it can already use .tap files. I can use it with my Timex Sinclair 1000 though. I don’t know if I will get any of the other compatible computers in the future, but I don’t currently have plans to.
I like the old 8bit computers. Being in the US, the ZX Spectrums are not really around here. I while wouldn’t be against getting an original Spectrum 128, I like building things. They also make reproduction cases based on the original 16/48k Spectrum case. I found the DonSuperfo’s reproduction Spectrum board designs. He made a 48k reproduction as well as he has several designs for 128k Spectrums. I found the ZX Nuvo 128 Rev 4A design of his. This version is his 128k based design with a DivMMC built in, and it fits in the 48k Case.
The Spectrum 128 portion is mostly through hole components. The DivMMC portion has a CPLD. There are a few surface mount parts otherwise, and I didn’t have any trouble with anything except the CPLD. The CPLD is very fine pitch, and was not designed for manual soldering with a soldering iron. My smallest iron tip still touches a couple pins at a time, note the smallest tip wasn’t the best choice. While I got it in the end, I do not intend to be soldering any more of those CPLDs with an iron in the future if it can be avoided. Due to that I am very glad I didn’t attempt the Rev 5a with a second even larger CPLD on it.
I used Don’s documentation on Github. To get the parts, I started by ordering a HARLEQUIN 128K REV 2D kit from ByteDelight. It is a starting point for the build. I started there to get the bulk of the parts from it, there are a few parts that were not needed. Since I am in the US, I ordered the kit from ByteDelight’s Ebay listing, which was the cheaper way to go due to shipping etc. If I ordered from his website, I would have likely purchased the “Parts Only Set (NO PCB)” option.
I would have went with the Rev 2d kit overall, except it doesn’t support a couple things, and I wanted the built in DivMMC. ByteDelight’s kit is great with the instructions that it comes with, but they are only available with the kit, and I could not get the BOM for the 2d at the time. Don has since posted the 2d BOM on the Superfo Harlequin 128 Facebook page files section.
I ordered my Nuvo 128 Rev 4a PCB from DonSuperfo by way of contacting him through the Facebook group. It can alternately be ordered from PCBWay’s Projects section. I didn’t need 5 of them, and I didn’t want to try to sell the spare PCBs somehow. Unfortunately for me the CPLD wasn’t included, which would have made the build so much easier. I think he does sell them with the CPLD, I just didn’t know to ask. The CPLD was $16.00 from Digikey, but it was quite difficult to install. It also took a bit of work to program, as I had no Jtag programmer around.
Since I couldn’t get the Harlequin 128 Rev 2d BOM at the time, I had to wait for the 2d Kit to arrive. Once I had the kit, I took the instructions from it which have the parts listing and the Nuvo 128 4a BOM from Github to find what parts I would still need.
Then I placed an order with Digikey to get the remaining parts, well mostly. I had to order the one obsolete ram chip from Ebay. I also had the various additional diodes and capacitors I needed in my inventory as well as a couple of the 74hc series ics. Below is a list of the parts I purchased, but a couple parts are missing, I will have to find the copy of the BOM I had edited to find the last few items to add to the list below.
1) UMC UM61512AK-15 a single one is needed as well, that is an out of production part. I ordered it from Ebay.
27) additional 1N4148 diodes are required.
Various capacitors are required that were not in the 2d kit. Some that were in the 2d kit had to be swapped due to available space.
I believe a couple parts are missing from the above list due to me having them in my inventory already. I will have to review the full BOMs. There were a couple IC Sockets that were required, and for some sockets I decided it was best to use machine pin header strips rather than cutting up regular sockets.
That is the parts to build up the Computer, minus the case and keyboard, which I sourced otherwise.
Building the Nuvo 128 4a:
I started with all the small low stuff. The AD724 NTSC/PAL Encoder was first. It came presoldered to the Harliquin 128 2D PCB, so I had to desolder it from there. I used my hotair gun for that. I then used my soldering iron to solder it onto the Nuvo PCB. I had thought of leaving it on the board and buying the AD724 from Digikey, but it was $26 just for one. Next the Diodes and Resistors. I think installed the Transistors and Resistor Arrays next. I did be sure to not build up parts around the CPLD though. I could have done the CPLD first, but I wasn’t up to it yet. I wanted to get in some soldering practice and work up to that.
On the board J9 is to switch between “Composite Sync” for RGB mode and “Composite Video” on the 9 Pin MiniDin. It is made with the pins shorted for “RGB” mode, making it so you can’t switch it. So I cut the trace on the bottom of the PCB. ”Composite Video” can be used as the Sync signal for RGB video depending on your display/upscaler. I was having issues with using the RGB “Sync only” signal with RGB, and I wanted to be able to use plain Composite Video as well, so I switched it to Composite Video. It my have been an issue with my upscaler’s connection at the time.
Next I put on the CPLD and after that the MicroSD Card Slot. Notice the missing Diodes by the MicroSD Card Slot, they were left off to provide room to solder on the Micro SD Card Slot. I then went back and finished the Diodes. The MicroSD Card Slot was easy to install, but that CPLD wasn’t. Even though the CPLD looks good in this picture, it did not work properly. I tested all the pins I could and used my microscope to view it, I couldn’t find any faults. I was able to program it with the JTAG J17 header there just below it, but it wouldn’t initialize once the Nuvo 128 was built. In the end, I had to desolder it (using hot air). I then cleaned up the pads and CPLD and reinstalled it, partially soldering with my soldering iron and partially with hotair. It then worked properly.
That is a MicroSD Card Slot. The CPLD is tiny and has a lot of pins. The header below it is standard 2.54mm pin spacing.
Nearly ready to install the ICs.
Note: the Keyboard Connectors are 1 sided and must be installed turned the correct direction (which is different for each).
Above about all that was left were the switches, and the 3 directly soldered on ICs.
Programming the CPLD:
I didn’t have a JTAG programmer. With some direction from people on Don’s Facebook Group page, I looked around and found how to setup a Raspberry Pi 3b as a JTAG Programmer. The guide was old, and the one required part for it to work is no longer part of the default pi os, I had to find an old clone of the Github repo to get it to install properly. After that I found they had an “updated” guide that was to work, but I couldn’t even get that to install properly. So at this point I programmed the CPLD. Directions I used: with the work around of finding the other repo: https://linuxjedi.co.uk/2020/12/01/programming-xilinx-jtag-from-a-raspberry-pi/ The “newer” directions, which are also linked in the above that I couldn’t get working at the time. https://linuxjedi.co.uk/2021/11/25/revisiting-xilinx-jtag-programming-from-a-raspberry-pi/
See the Programming Warning below..
Warning: As seen in the picture below I programed the CPLD “before” putting on any of the other ICs (except the video encoder). This worked fine.. But when I found the CPLD wasn’t working properly, I tried to program it again after installing all the ICs, and nearly fried the Pi. It seems it was trying to power the Nuvo 128 5V components by the 3.3V VCC pin on the JTAG programmer. I expected the VCC pin on the JTAG Header was going to be the 3.3V which only goes to the CPLD, as that is what we are programming with the header. It appears that the regulator doesn’t prevent reverse voltage back feeding from the “Output” back through it and out the “Input” pin, and nothing in the design otherwise is setup to prevent it. It melted the casing on my dupont connectors and melted the VCC and Ground pins loose in a matter of seconds. As I was watching the Pi’s Video output it listed a Low Power warning, which warned me of what was going on. I tried to pull the jtag header, and the VCC and Ground wires came right out of the dupont crimps. Thankfully it didn’t do any damage beyond the connectors. To verify the programming, I then reconnected the JTAG header, but “Except” the VCC pin. I powered the Nuvo 128 by it’s main power jack, which powered up the CPLD. Then the JTAG Pi programmer was able to read the CPLD and program it, although it was already programmed properly. That did verify it was likely working and that it was soldered on as well as before at least.
Finishing Up the PCB:
Once the CPLD was programmed, I soldered on the 3 ICs and installed the other ICs in the sockets.
I missed installing the top IC before testing the board, it was not critical though. It is for the Joystick port.
The buttons were not installed yet, and I was waiting on the 5 position dip switch. I rigged up a minimum Composite Video connection for testing. With the dip switch not installed, Don’s ROM defaults to the Test ROM and the DivMMC disabled.
Composite Bodged in
Further testing revealed that the DivMMC was not working. That took me a good while to sort. I examined the soldering, checked for shorts and found pinouts for the Rom and CPLD. I traced the pins for the DivMMC ROM, Ram, and CPLD unable to find an issue. The CPLD pins are so small that it was difficult to verify I was on the right pin though even with test leads with very sharp tips.
I eventually decided to remove the CPLD and try putting it on again. I removed the JTAG programming header, as it was in the way and was going to be melted with the Hot Air gun. I covered up the nearby parts and sockets with Kapton tape to help prevent melting them. After I used hot air to desolder the CPLD, I cleaned up the pads and the CPLD pins and resoldered it on. I did then connect up the Pi3 to the JTAG header… see the warning above, I nearly fried it due to how VCC seems to be wired on the PCB. After verifying the CPLD was programmed ( I downloaded the programmed data to the pi, then programmed it again, and downloaded it again then compared the downloaded files.). I then put the properly prepared Micro SD Card (must be formatted properly, and must have the esxdos files of the matched version on it https://www.esxdos.org/index.html), and it worked!
Running a demo from the DivMMC
Preparing the Case:
Now that it was fully working with the DivMMC and the 5position Dip Switch had arrived, it was time to make the PCB fit into the 48k case. The opening where the 9 Pin Mini din ( old rf opening) needs enlarged along the bottom edge a bit. The opening needs made for the DB9 Kempston Joystick port. The opening for the Micro SD Card Slot needs made. The two openings for the buttons on the side need made. Since I wanted to use the Multi ROM, I wanted the Dip Switch to be accessible as well, so it needed an opening. I have since seen another of Don’s boards done by someone that put the Dip Switch on the bottom of the PCB, and cut out an opening in the bottom. That looked very neat, I don’t know where that would align on the Nuvo though, and it was well after I finished this build and had my opening in the side of the case for the DIP Switches.
For the Buttons, I kind of messed up and put the openings lower than they should have been, then I decided to “slot” them “upward” toward where they actually should have been. Since I had those odd openings I need to come up with a way to make them look a bit better. I made up a model for a button cap in Tinkercad. I printed it out of TPU. It fit on the button stems perfectly, and after the first test print, I made an adjustment and they worked great. They stick out just enough to press, they close the holes up well, and the TPU has just a tiny bit of give. The MicroSD Card Slot came out great. The DIP Switches are accessible even if it is not quite a perfect opening.
On to the Keyboard:
It was on to the Keyboard. I had found there is a replacement “Velesoft” anti-ghosting microswitch keyboard for the 48k case. I wanted that rather than the membrane keyboard. They are available from ZXRenew.co.uk who does the Reproduction cases such as I am using as the “Zelux”. AmericanRetroShop on Ebay in the US sells the Velesoft keyboard labeled as the MechBoardZX. Bytedelight also sells the keyboards, again not in in the US. I purchased my case and MechBoardZX from AmericanRetroShop due to shipping etc to the US. From what I see they look to be identical PCBs, all labeled up with the Velesoft design and just different branding otherwise on the silkscreen.
I did order the baseline keyboard without the LEDs. When I went to put it together though, I had decided to install the LEDs. If I decide I don’t want them on, I can always unplug the power to them. I had the LEDs and required resistors in my inventory so it was just a bit more time to install them. I couldn’t find what resistors came with the kit, I used 1k resistors I believe. In the end I think the Blue LEDs could have had a slightly higher value resistor, while the Green LEDs would have been better with a slightly lower value resistor. With the Nuvo 128 4a, it has a 5V Power header by the left Keyboard connector labeled as J15. I expect that header is intended for this type of use. I based my resistors on using 5V for the power, so there is no need for a Buck Converter Regulator as is generally included in the LED kits. I don’t see why they do that, and don’t setup for 5V power.. Yes the power losses are a little higher, and for an original ZX Spectrum, that may be an issue.
The PCB is very thin, and flexes. To keep it in place while I worked, I taped it to my silicone work mat. That way I could move it on my bench, but it wouldn’t move on its own.
Baseline KitConnected up, including 5V Power J15
Finished Setup:
Now that the Nuvo is finished and I built a new GBS Control with a RGB SCART Input on it, I can run the Nuvo 128 in RGB to any of my VGA, or HDMI Displays with audio. I don’t plan to primarily use it with my bench monitor. I can use this over on my desk that I keep setup for use with my old computers. I also built up a MAXduino kit, which I customized the case to be a nice match for the system. It is a quick and easy build from the Retro.care kit. It lets me load some games that I only have in the .tzx format which is not compatible with the DivMMC.
Some Notes.
C6 is a very tight fit, I had to find a capacitor small enough to fit there. It wedges in between U46 (the Regulator), J4 (the power jack), and SW1 (the 5 Position Dip Switch). It seems that could be adjusted with a bit of work, as the other versions don’t have it quite so tight. The value the capacitor is makes it a bit tougher to find that is small enough in diameter.
C28 and C29 need to be fairly small as well. In my case I had some rather large diameter ones that are very short, so they are raised off the board to clear the components around them. They can be found though, and thankfully I could use the ones I had due to them being so short.
U57 and U53 are a bit too close, they rub each other when installed. It just feels awkward.
As mentioned above the JTAG header J17 for programming the CPLD will backfeed power through the 3.3V regulator to the rest of the Nuvo board. This caused the JTAG programmer to try to power the whole ZX128 after the ICs were installed. I did find that something such as a 7805 Regulator will have that problem if power it applied to the “Output” while no power is on the “Input” side if there is a load on that “Input” side that can draw power. With the Nuvo 128 there is a lot of stuff on the 5V Input side of the 3.3V Regulator. I think a Diode just before the Regulator Input would prevent that, and as the DivMMC CPLD doesn’t draw much power it shouldn’t be a big deal if the 3.3V regulator can handle the slightly lower input voltage that would cause.
J12 for the ESP8266 module has the VCC Pin wired to the 5V Power rail. The ESP8266 Module that fits there is a 3.3V device. Some are “labeled” as “3.3V/5V” but I think they are “mislabeled” as none of them that I have been able to find have an onboard 3.3V regulator. The Nuvo128 has a 3.3V regulator for the CPLD, it could have been wired to J12. Provided it can handle the extra load. I have thought of modifying the board to get the 3.3V over there. I do have the module, the 3.3V powered one, but it doesn’t seem worth the trouble. It looks to be of limited use.
I don’t understand the choice to wire the 9Pin Minidin up with a Jumper J9 to switch Pin 4 between “Composite Sync” and “Composite Video” (which is defaulted to “Composite Sync” . The pinout is based on the Mega Drive 2 / Genesis 2 pinout. With the Mega Drive 2 / Genesis 2 9Pin Minidin port Pin 4 is “Composite Video” and Pin 5 is “Composite Sync”. On the Nuvo 128 Pin 5 is not connected to anything, and Pin 4 is by default “Sync” not “Video”. I expect there may be at least small quality improvement when using “Composite Sync” for “Sync” instead of “Composite Video” for “Sync”. It seems it must be small, as it looks that most of the RGB SCART Mega Drive 2 cables don’t use “Composite Sync”, they use “Composite Video”. I thought of wiring Composite Sync to Pin 5, but the output is great with using Composite Video for Sync so it doesn’t seem worthwhile. The little change of putting Composite Sync on Pin5 and removing J9 seems like a reasonable idea. I also find it a bit odd to use that type of cable, when the Resistors and Capacitors need to be removed from the cable to make it work properly with the Nuvo. Now if I use that cable by accident with at Genesis 2, it won’t do the upscaler, or display any good I am sure. It does make finding an “almost ready to use cable” for the Nuvo easier though.
Now that I have built a ZX Nuvo 128, I have a need for a good option for connecting up the RGB (RGBS) Video from it. The Composite Video output of it is pretty good on my 10″ LCD Monitor that I have on the work bench. The composite doesn’t look as good on some other monitors though.
With the GBS Control I built awhile back to use with the Commodore 128 RGBI to RGBS I had not included a SCART RGBS port or have an option for Audio passthrough. I just made it up to work with a standard VGA Cable. I also didn’t included the optional .96″ LCD Display and Encoder. This time I want to include those items. I am also going to place the SI5351 in a different location. I didn’t like putting it on the heatsink like I had last time. That heatsink does get warm with use, and having the board on it does reduce the heat dissipation. There will be a Switch to toggle in the Resistor between the Sync and Ground for 75 Ohm Sync Termination Enable/Disable. With SCART it will have audio passthrough. Due to that, I am also building it with a 3.5mm Stereo Audio Input/Output Jack. There is also a VGA to HDMI Adapter inside the case with audio wired to the 3.5mm and SCART ports. I can still use the VGA Output, but if I use the HDMI Output I will have audio passthrough from SCART (or the 3.5mm jack). If I use VGA as the Output and SCART for input, I can use the 3.5mm for Audio Output. If I use the HDMI as the Output and the “VGA” Input, I can use the 3.5mm jack for Audio Input so it will then output through the HDMI port.
I looked for a case that included this exact setup. I couldn’t find a full featured case that used the ESP8266 NodeMCU board form factor that Voltar had used, and I have a spare of. I found cases that use a smaller footprint ESP8266 Board with all the ports and features I wanted. They also often used a different SCART Connector than I have though.
I found a case that is similar to the last one (It is listed as a “remix” of it, but is nearly a full reconstruction I think) I had used previously. The remix also included a SCART port, which is the type of port that I have. It also had the option for the HDMI adapter, and being based on the other case I found there are 3 variants of HDMI Adapters that had mounts already made for them. The first HDMI Mount I printed I thought was the right one for my adapter, but I found out it wasn’t. There are 2 very similar looking HDMI Adapters, and mine was the “other one”, I found a mount that fit it. I tweaked it a bit to make it a slightly better fit. It turned out to have smaller screw holes, so I split it when installing it. I went back and resized the holes and reprinted it. It now fits quite well.
The case didn’t have an audio input (except by the SCART Connector), but that is an easy 1/4″ hole to add. This case did not have the LCD, or Encoder option. It also didn’t have spot for a switch that I wanted for the Sync resistor. It was simple to add the 3.5mm jack, and easy to add the Encoder, as they are simple holes. I added the spot for the switch in the little part above the VGA output port. The case is 3mm thick, which is a bit much though for the Encoder and 3.5mm jack, but it just fit. I printed the base case part to check it out and found a couple issues with it. The GBS board I have was a very tight fit, and when I test fit the board I almost couldn’t get it out. I ended up sanding the PCB down just a little, which makes it fit better. The SCART port is a bit of a problem to get in due to the large pin RGBS connector getting in the way. The Component RCA Jacks openings are slightly offset to the right.
After building this GBS Control up, I went back and relocated the front VGA and Component holes over to the left where they belong. I relocated the SCART port further toward the back of the case. I also thinned the front of the case by 0.25mm, due to the tight fit of my GBS board, this also gives the Encoder and 3.5mm Jack a tiny bit more usable screw thread to secure them. I printed a new version, the holes on the front line up properly now, the SCART still has a bit of an issue with the large RGBS header being in the way. It isn’t as bad now as the screw won’t run into that connector. For this build I had removed the RGBS port as it was in the way. I also redid the HDMI Port opening in the back, I didn’t like the tapered/feathered edge on it. I can’t move the SCART back any further than I already have as it will run into the back case screw.
Adding the .96″ LCD, it was bit more complex. I had to find some dimension specs, and I made up a model of it in Tinkercad. It gets a small bit oversized to allow room for the part to fit. My LCD is 1mm narrower than some other similar .96″ LCDs. I had to work out where everything else will be in the case. Where the ESP board will be blocking space, where the VGA to HDMI board will be, and also where the back of the Encoder will be. I printed a test print of the LCD holder part. The LCD fit, but that 1mm wider version didn’t. I reworked my 3d model of the LCD to be 1mm wider on the PCB, but it did not matter on this part, as there is no Rim up around the PCB with this part. I made another minor change to the case to accept the LCD where I wanted it. The LCD is optimally installed with four 2.5mm m2 screws. You can use 3mm m2 screws, be careful not to bottom them out and damage the case making them show through the top.
I didn’t realize it at the time, but when I went to put the VGA to HDMI adapter into the mounting bracket, it did not fit properly. There are apparently (at least) 2 VGA to HDMI adapters that look very similar externally, but the boards are a bit different. The one that was included with this case was not the correct one for mine. I did find one that was made for my adapter. I did make changes to it, I put in a relief cavity to let one of the ICs to rest in to prevent putting pressure on it with the clamping plate. That could cause failure over time. I also put some “slots” in the bottom of it looking similar to the one that did come with this case, I then found the screw holes were smaller, so I split the part when putting in the screws. I revised that and reprinted it with the larger screw holes. I swapped it out and the screws didn’t split it out this time.
The case is cool looking, and there is a good attention to how to make it work. It feels sturdy, mostly due to being thicker than the case I used last time. It is thicker than most cases I make myself, but for what it is, I figure it is worth the extra filament. I don’t like seeing into the case internals through the VGA ports, I may make little thin plastic sheets that close those gaps. I had to order the proper length screws to put the case together, as I didn’t have any that long. The model designer did specify the proper screw type and length.
This second GBS Control is functionally about the same, it has more connector options and HDMI Output internally. The VGA output also still works, I left it on the board and used the output header beside it to get the RGBHV into the VGA to HDMI.
The 3.5mm audio jack can either be used for input or output. If I am using SCART as the input, that will be inputting audio. If I want to use SCART with a VGA monitor, I can then use the 3.5mm audio jack as the audio output to speakers. If I am using RGBS/RGBHV VGA port for input (or component) and want to use HDMI with Audio for the output, then I can input the audio into the 3.5mm audio jack.
Overall, I had to pull pinouts for the SCART, and find the Pinout for the RGBS header that the included pigtail wire was for. I had to check the pinout of the 3.5mm jack I purchased. I also had to trace out the VGA/RGBHV pinout on the GBS Board, to verify it as it is labeled properly. For the VGA to HDMI adapter, I had to desolder the 3.5mm jack usb port, and the VGA port. I lost the HSync (or VSync) pad in desoldering the vga connector from the VGA to HDMI adapter. I was able to trace that down to a pad on the other side of the board. I had to trace out the pinout of the 3.5mm Jack on the board as well, and found I lost one of the Right audio pads too. There are 2 Right audio pads and 2 Left Audio pads so that worked fine as well. The board seems a bit delicate, but removing those connectors can be hard on any board. There is another type of VGA to HDMI board, the one used on the Super Gameboy Console project, there is a bracket for it out there as well, it has a standard through hole VGA input and audio jack. After building this second GBSControl, I went back and rebuilt the first one adding the SCART, HDMI etc. For that one I used the other HDMI Adapter. It was easier to remove the VGA and through hole Audio jack, but the USB Power had to be removed, and that was difficult to do without ripping off the pads (I lost one of the ground pads, but there are plenty of ground pads).
The LCD didn’t work when I connected it up, I flipped SDA and SCL and the LCD worked. I wired the Encoder as shown in the diagram on the GBS Control site, with the recommended capacitors, but it doesn’t work very well. For the rebuild of the other GBS Control, I didn’t include the Capacitors on the Encoder, it seems to work better. I was thinking of putting on some 100nF capacitors instead, but as it worked better without any capacitors, I didn’t bother with them.
To prep the GBS board, I removed the large pin RGBS header, as it was in the way of the SCART and not needed. I removed the RGB adjustment pots. I removed the headers over where the ESP gets wired in. I also removed the buttons, as I was unsure if they would get in the way of the Encoder (they would not have). The one capacitor was damaged (dented), so I also removed it and swapped it with a spare.
Once all the parts and boards were prepped, I tested the GBS before modding it. It posts a splash image when in default mode. That worked.
Then I added the 4 surface mount capacitors. I added the wiring for the ESP board. I again used two angled pin headers for the Ground pins to give a good secure connection to the GBS board.
The LCD was easy enough with just 4 wires with a header. For the Encoder, I wired it up with the suggested capacitors. The Encoder didn’t work very well in testing, below I also show that I added the new connectors etc to my original GBS Control, with that board I didn’t put on the Capacitors with the Encoder, and that is working better for me. I will probably remove the capacitors from the Encoder on this unit the next time I open it up.
For the HDMI Adapter I desoldered the VGA the Audio jack and USB Power port. I built up the HDMI adapter wiring. I didn’t have a large enough connector for the VGA output header, so I made up 2 smaller ones, the first for the RGB and Ground, then a smaller 2 pin one for H Sync and V Sync that gets plugged in to the right of the larger one. The board is labeled with R G B and H V on the header, which is correct, the other unlabeled pins are Ground, or mostly are ground on that header. I used the provided pigtail for the power header and soldered that to where the usb power port was for the HDMI adapter to power it.
ESP Board PreppedClock board with Kapton and foam double sided tape.This didn’t work very well with those capacitors, I am suggesting not using the capacitors on the Encoder.
Below I have the baseline GBS Control. This has the ESP board installed, the Encoder, the 4 pin header connector for the LCD screen. The 4 added surface mount capacitors. The RGB potentiometers are removed, they do have the jumpers installed from the bottom of the board, don’t forget them. The jumpers on the RGB potentiometer locations were put on the bottom of the board, as I am placing the Clock Generator board on top where they used to be. When I had this this far along, I tested it to make sure it was still working.
Next I installed Clock board. This new placement is recommended currently on the GBS Control wiki, and the board just fits in there. The first board shown is an Adafruit branded board appears slightly larger, but I don’t have dimension of it. The person doing the alternate placement used the same type of board I am using had cut the board down smaller, more in one dimension than the other. I expect the reason for chopping it in the narrower dimension is to get more clearance to the TrueView IC pins and heatsink, as it is quite close. I had missed this was to shift it to align with one of the Ground Through holes in the board from the removed Potentiometers. The smaller generic board I used does otherwise fit perfectly without any modification if you use a ground wire. You may be able to get alignment to that ground point though by removing the RGBS connector, but I missed the note about the Ground pin while doing the build. I placed 2 layers of Kapton Tape to the bottom once the wires were soldered on. I then put foam double sided tape to hold it in place. Then I put in the short wires to the ic pin on the corner. I wired into the capacitor the same as before for power, except I put power to the power and ground pins. I am not sure why they are telling you to add the 3.3v to the one capacitor, the board supposedly runs as 3v with a LDO Regulator that can be powered by 3.3v. So I felt it best to power it the way it was designed to be powered.
The last parts all plug in. The HDMI Adapter took some tracing out the pinout to know where to put the wires. I used a bit of ribbon cable with connectors that I crimped on. I do not do them very often, so it took me a bit to figure out how to crimp this type of connector properly. I used the power pigtail to power it. I used the RGB pigtail to wire to the SCART Connector. The switch and resistor for the Sync pin is wired to the Sync pin and Ground on the SCART Connector. I did wire together both halfs of the switch, it just doubles up the connection path incase one half starts making poor connection with use. It is not easy to see, but the SCART Connector has all the Ground pins wired together. Then the 3.5mm audio jack is wired into the SCART. With the audio also running over to the HDMI Adapter from the SCART Connector. The HDMI Adapter ribbon cable has some Liquid Electrical Tape on it to tie it together. That was mostly as I had lost a pad for H or V Sync and had to run a little 30awg wire to the top of the board and solder it then to the proper wire in the ribbon.
The 12pin JST PH (2.0mm) connector by the VGA output is where the HDMI Adapter is connected to. The pin out is Red, Ground, Green, Ground, Blue, Ground, Hsync, Vsync, and 4 more pins that we won’t be using. As I didn’t have a 12pin JST PH connector, I used a 5pin connector wiring in R, G, B and 2 Ground pins. Then for Hsync, and Vsync I used a 2pin connector, which fit in nice beside the 5pin connector. You can add a spot of Hot Glue if you like to hold it. Alternately if you have an 8 pin, or longer plug you can do it all as one, and it will be more secure. I linked a couple suggested connectors and the tool below, not any affiliated links or anything. You could solder to the pins, or maybe get or salvage a cable from somewhere else. I used part of a salvaged ide cable, which a good size of wire for the crimp connectors. Otherwise I use 30awg solid core wrapping wire, and 24 awg silicone insulated stranded wire, along with various other bits of regular scrap wire from my stash. The wrapping wire is small and easy to use to solder to small pads or ic pins. The stranded silicone insulated wire is very flexible, easy to strip, and the insulation doesn’t melt, so I splurged on some the other year.
SCART Connector, 3.5mm Audio Jack for Input or Output depending on usage. Sync to 75Ohm Switch and HDMI Adapter assembly.
The wiring on the VGA to HDMI adapter may vary, as there are some variations in the connector. With the adapter above, Red, Green and Blue were on the top of the board with Hsync and Vsync on the bottom of the board. I checked them with a continuity mode on my multimeter to verify I had it all correct. There are of course numerous Ground pins on the VGA connector. For the Audio input to the HDMI Adapter, I just used my multimeter again to test the connectors on the removed 3.5mm jack, which I was unfamiliar with the footprint for. While the 3.5mm jack had the build in “switches”, both the switched and non switched pads were wired to the inputs. That was good, as I lost one of the audio input pads closest to the hdmi adapter.
The last bit is easy, just screw the LCD to the top cover. Then it is connected with the included pin header. Using some M2 x 2.5mm (3mm max) screws to install it. The Pinout is sometimes different for the LCDs, so always wire it based on the Silkscreen Labels on the LCD. The Silkscreen Labels though are on the “front” side of my LCD, once installed I can’t read them.. The Dupont 2.54mm connectors can be purchased as various lengths and used for breadboard wiring and such. You can buy the crimp tool for them. I purchased a SN-28B Ratcheting Crimper, which doesn’t work for the JST PH 2.00mm crimps.. so purchased the SN-01BM Ratchet Crimper I have both sets now. I am wanting to try the SN-01BM with the Dupont 2.54mm. The only difference in the Crimp tools is the Die Inserts, so you can just use one crimper and get different Dies for them if needed. There are other non ratcheting crimpers that are a bit cheaper, I tried one but didn’t have much success with it. Other people have said they are great, and I find that the case with such tools, using them incorrectly they smash the crimp, or cut the wires off.. Doing them correctly, they work great. Putting the crimp in from the wrong side, crushes the connector and usually cuts the wire, but putting them in the correct side it just works.
The complete internals. There is a good bit more inside this GBS Control build, The filament I used is Overature Matte White PLA. It is a little bit of an odd filament, not glossy and more opaque (but not fully with LEDs behind it). It gave the unit a unique look, and it feels sturdy. It also looks good with my White ZX Nuvo 128 in the ZX Spectrum 48k White reproduction case.
I closed it up and did some testing with RGB Video from my Nuvo 128 to HDMI on my bench monitor. It looks great and the audio sounds great, all considering the monitor it is connected to that is.
I had all the parts that I needed. I used another type of HDMI Adapter, and put it in the revised case.
Below are most of the new parts laid out. It is hard to make out, but the required resistor is wrapped between the sync and ground pins on the large rgb header partially blocked by the new 3.5mm jack. The HDMI Adapter wiring had connectors JST PH (2.0mm) connectors crimped on. I didn’t have connectors that were long enough, so I used a 5pin for the RGB and Ground, then a 2pin connector for the H-Sync and V-Sync pins again. The wiring on the VGA to HDMI adapter was a bit different as it is a traditional through hole vga port, but it was easier to map out as that is the standard vga port footprint. For the Audio, it was easy to check left and right on the 3.5mm jack, it had 2 pads for Left and 2 pads for the Right channel.
The SCART port is relocated further back on the case to help it better clear the large RGB Connector. If you look at the pictures, you may see in the White one above, the one SCART Screw would run into one of those RGBS pins if the connector was installed. The front of the case is .25mm thinner as the GBS board was wedged tight in the white case, which did make it nicer for the 3.5mm and encoder mounting with just that little bit more thread usable to screw in. The front input port openings on it are now properly lined up with the Component RCA Ports. The .25mm thinner front of the case gives the GBS board that little bit more space, but oddly the other GBS board seems to have more clearance. The Grey case is the revised one. The top didn’t print as nicely in the Grey.
Back, mostly the same.Component Openings AlignedSCART back for better internal Clearance.Tops are the same other than how well they each printed. I had the Z Height a bit too low on the Grey one, so the finish is not as good. The Grey would still show the lines more than the white due to the type of filament though.
With the large RGBS header on the board, it did get in the way of the one corner spacer. That I had to shave down a bit to get it to fit properly. I could have removed that header like I did on the white one above, but I didn’t want to go to that trouble. It was minor thing to file the spacer.
RGBS Header in the wayShaved SpacerShaved Spacer Installed
The SI5351 board was relocated. This was almost required, as there was very little clearance to the HDMI Adapter with the prior location glued to the top of the heatsink. I also prefer it as that heatsink does get warm with use.
Kapton and Foam TapeReinstalled
I did use one of the other style of HDMI Adapters in the Grey one. I had a couple of them. It is the type used in the Gameboy Console project, so I had two more of them laying around. After looking at it, it is not identical to the one I used in the Gameboy Console project, the regulator setup is different, some parts are not present. This adapter was easier for me to get the VGA and Audio ports off, but the the type of USB ports for power was more difficult than the other style. I prefer using this type of HDMI adapter, as it lines up to the hdmi better and feels more secure. I will also be more likely to reuse the connectors I pulled from it.
Alternate HDMI AdapterUpgrades completed.
I think this one looks a bit neater internally, I did get the wire lengths down just a bit, which helps it be less cluttered. It still has a lot of wiring in it though. You can see the buttons on the pcb don’t have any issues with the Encoder being above them. Sure they won’t be used, but there was no reason to remove them.
I am going to reprint the Grey top case at some point, plan to do it with a multicolor print to fill in the GBS C text flush to the top. I tested this one with the Nuvo 128 as well, testing both HDMI with Audio and VGA Output. It worked just as well as with the White unit except the Encoder seems to work better without the capacitors. This GBS Control will go back on the desk where I keep my Commodore 128 connected for use with the RGBI to RGBS adapter. I plan to use the new White one for the Nuvo 128 mostly if I use it somewhere other than that desk.
2x M3 x 10 mm (For SCART Connector) Alternately use longer screws with Nuts if you prefer.
Depending on which VGA to HDMI Adapter you use. Either 2x M3 x about 6mm for the smaller one, or 1x M3 x 6mm with nut for the larger boxy type Adapter (in the Grey unit)
After building the RAD REU for my Commodore 64/128 I found out that the Nuvie videos were made for PAL systems. My two Commodore 64s and 128 are NTSC models. I didn’t make the RAD REU to watch those, but since I wanted to see what they were like. I started to look around for a reasonably priced PAL C64. I came across this one listed as not working with a switch issue at least. It also doesn’t look great.
It arrived with a little paint on the lower left corner, some cut marks along the lower case and badge. Such as hobby knife or pocket knife. The cuts look intentional, but I don’t see a reason or pattern. The case overall looked reasonable. I opened it up to inspect the stuck switch and overall condition. It was rather dirty inside, the cartridge port guard was somewhat rusted. A little rust on the RF Module. It was dirty like it been stored in an attic or shed. I tested the jammed switch and got it to move to a position where it was switched on. Powering it up the system seemed to work fine. I did some testing but not a full diagnostic test.
I took the system apart to clean it and work on the power switch.
The C64c after repairing the power switch and cleaning the board up.
This is a Short Board. I find it interesting how much less complex it is than my other two Commodore 64s.
I do have some brand new power switches for the C64, but these switches can be taken apart and be fixed, at least sometimes. I removed the power switch and took it apart, the grease in it was gummy and sticky making it not operate properly. The switch didn’t show any significant wear internally. It did take a fair bit to get the gummed up grease out of it though. I added new silicone grease and reassembled it. This blue power switch doesn’t have a “nice click” to it like my other Commodores, but as far as I can tell, it is working properly. It now moves nicely, and makes very good connection across the switch pins. I have since seen someone comment in a video that the Blue switch doesn’t feel or sound the same as the other Red ones, so it seems this is just one of those other types.
This got the computer working fully, or appeared to. While I had the board out, I did clean it with IPA. I cleaned as much of the rust from the cartridge shield as I could. I did not reinstall the clip on cardboard RF Shield. The image above is the board after cleaning and fixing the power switch.
For the case I washed it with dish soap and warm water. For the white paint on the case, I used 91% ipa, which easily removed it. For the cuts into the case, they were shallow, but I could “feel” the edges when touching them. I decided to use a hard plastic stick, and “rub/burnish” the scratch down. That pushed the raised up sides of the scratch back down and made it so that I couldn’t feel it any longer. There were a number of them all mostly below the keyboard. This also made them less visible, although if you look closely you can see them. The case is in good condition overall beyond that, the clips are intact, it is not cracked or modified.
Those are the scratches after burnishing them.
The dirty keyboard.
I also disassembled the keyboard, just taking the keys and springs off with a keycap puller. The rest of the keyboard assembly was cleaned with Windex, a brush, and qtips and paper towels. The keyboard frame and pcb was not disassembled, I waited to test it before deciding if it needed opened. The keys were washed with warm water, dish soap and a toothbrush. There were some springs that were a bit rusty, those spring were wiped down and put into a small cup of vinegar for about 20 minutes. They were then rinsed with water, wiped down and dried. The next day after the keys were properly dry, I reassembled the keyboard. It was connected to the computer and tested and found to be working properly.
The video output on the C64c was good on Composite. There are some visible jailbars, but it is not awful. I had more of TheRetroChannel’s RF Replacement boards for the C64Shortboard (and C128) as I installed one on my Commodore 128. I also had all the parts to build one, so I decided I would swap out the RF Module. With doing something like that, I decided I would also recap the board.
The audio jack on the board was modified to sit lower to the pcb. The jack would have otherwise been centered at the same point as the SVideo port. With the audio jack lowered, I was able to keep the board a little bit more level than I would have been able to otherwise. There is no modification to the C64 mainboard or case for this mod. The L-H opening is not modified and neither is the RF opening. I kept the modulator, just incase I want to put it back someday. To get proper alignment, I test fit in the board and case. Once I get the alignment correct, I solder in one of the 4 mounting pins, then test fit it again. Then solder the next mounting pin and test fit again. Then finally I solder the remaining two mounting pins as well as the 8 pins for the signals to finish the installation. I then tested output of the Composite video, it looks pretty much the same as before. I then tested the Svideo output and audio output, which both worked properly. The Svideo is sharper as expected. Also the Chroma/Luma is still on the normal display port as well as Composite video. There is a jumper on the new board that does disable the color signal to the Composite, which is to clean up the Svideo output a little, but I keep it installed. There is also the Chroma Luma bypass option, which I did not do. The board supports doing Stereo Audio out to the audio jack if you have dual SIDs, which I don’t have. It also has a Hard Reset circuit on it, that you either install a button in place of the Audio Jack or use a button mounted somewhere else by the one jumper header on it. At this time, I do not have the Hard Reset connected, but I did populate that part of the board incase I decide to set that up at some point. I don’t like to modify cases, so I don’t have anywhere to put a switch at this time.
The video wasn’t bad on this C64c, and after the change, the Composite looks pretty much the same. With the Commodore 128 there was a significant video output improvement though. I wouldn’t have put the mod, except I had the spare boards. It may be a little better, and it does make it easy to connect to SVideo. I do have a single Commodore 64 to Svideo cable, but I have 4 computers now, so not having to have more custom made cables around is nice if I want more than one of them connected at a time.
When I recap a board, I test the new capacitors before installing them. I then test the replaced capacitors and compare them to the new test results. With this computer, I didn’t find any capacitors that were obviously going out. Sometimes I find a few that seem to be out of where they were expected. I work to use proper replacements from good manufactures and sources. I see no reason these capacitors should fail as long as I have use for the computer. The old capacitors are 33 years old now, they may not have held up at some point in the future. My hand isn’t as steady as it was, and I can’t see the part as well as in the past. I can do this work now, I don’t know about in another 10-20 years what it would be like. Maybe the computer won’t work in that time, maybe it will..
I keep forgetting to get good before pictures of projects. There wasn’t much to this, I would have liked to have some pictures of the switch internals. I have been doing similar switch tear downs for years, it isn’t complex, although it is good to carefully look at the parts and how they come apart. The recap was standard, this board did give me a hard time with the thick ground plane though. I don’t remember having quite as much trouble with the other two C64s or the C128 on the ground plane. The cleaning is standard, I used dish soap and warm water in the bathtub for the case top and bottom. For the keycaps I use a bucket of warm water with dish soap in it. If I am not washing something large like the case in a sink/tub I will often use Windex instead. For sticker residue I use WD40. I only use IPA to get marks off if nothing else has worked, I also tend to not use it on dark plastic. IPA can damage the finish of some plastics and can make visible marks on dark plastics sometimes. I use IPA to clean circuit boards and metal areas. I have also started to use 99% IPA instead of the 70% or even 91% IPA to clean flux. That has shown to leave less residue, and break down flux much easier.
The RAD REU Nuvies do work with this PAL C64c. Now to get Sam’s Journey? Which is one of the reasons I wanted a REU to start..
Someday I may try to retrobright the keyboard. The case itself is not very yellow, but the keys are.
Muldrf's Hobbytronic 