Another Pi1541

I now have three working Commodore computers. Two 64s and a 128. I felt I wanted to have a second Pi1541. I didn’t have a non repairable 1541 laying around this time though. I do now have an Ender 3 Pro 3d Printer though and a little experience in working with it and 3d models. This gave me the interest in making a much smaller Pi1541 that looks a bit like the 1541ii. I figured that styling fit better with my Commodore 128 as well.

I didn’t need another Tapuino. There was talk of Steven adding .tap support to the Pi1541 back when I built my Pi1541 & Tapuino. That seems to not be making any real progress though so far, but it may yet happen. It may have and I missed it. Steven White and any other contributors have done a great job with the Pi1541 though. It is a great thing to have around.

My first Pi1541 case had so much room that I wanted to make more use of it, it has a 7″ Composite LCD than can be toggled between the Pi and an external input, an internal mono audio amp that can be toggled from the Pi (with a simple mixer to mix the stereo from the Pi) to an external input, it also has access to the USB, Network and HDMI from the Pi, as well as a bare Tapuino. It has controls on the front panel for the Pi1541 and Tapuino functions, as well as the SD Cards for both the Tapuino and Pi. I can take it and one of my Commodores and use it as a portable 7″ monitor with Audio for the Commodore 64 or 128. I can swap the SD Card and use the 7″ LCD for the Pi and run any other Pi OS, or connect the HDMI to a TV and use another Pi OS be it RetroPi or Raspbian etc…

This one was built to be more like the common Pi1541s out there. To be rather minimal in size, but do the job.

There has been a problem for me and the Pi1541 in that the Pi3B+ has gotten expensive with the release of the Pi4. I guess it is supply and demand. The Pi4 has a different architecture so it can not work as a Pi1541. I am betting there are quite a number of other projects that probably are in the same situation. Steven did come out with a Pi Zero version for the Pi1541, and as I was going for “Small”, and these are cheap I purchased one for my new Pi1541. Then I found out you have to overclock it, and it doesn’t support all of the features that the Pi3 does due to the more limited cpu and ram it has available to it.. So that idea was scrapped. There are other Pi3s though that are still more reasonably priced and support all of the same features with the Pi1541 as the Pi 3B+. So that brought me to getting a Pi 3 A+. They are slightly less powerful than the 3 B+ model, but they can still be purchased in some places for $25.00. Granted I can currently get a 3 B+ for $35 at http://www.adafruit.com which is where I purchased my Pi 3 A+ at for $25. Maybe there is less of a shortage right now. I still have a hard time spending $35 even when you can buy the more powerful Pi4 2gb for the same price (and the 1gb model for less)..

The next thing was to find a case design that I liked. I don’t like having bare boards laying around. I also don’t like simple block cases a lot of the time. I came across a case design on Thingiverse that I mostly liked.

https://www.thingiverse.com/thing:3127040

Like I said I “mostly” like the case. Mike from thegeekpub used this case for the Pi1541 he posted a video on. It is styled after the 1541ii. It is listed as a “work in progress”, and kind of is. I made quite a number of mostly small changes to the case for my needs. Some were functional changes, some were cosmetic. The case is a 4 part case in the current design, the pictures at Thingiverse don’t all reflect that.

My prototype print. The only change being the rectangle LEDs at this point.

So let us go with the cosmetic first. I wanted Rectangle LEDs like the real 1541ii. My skills with 3d modeling are limited. That was one of the points of this project though, it was to help learn a bit more in that area. I use Design Spark Mechanical for 3d modeling. I have used Tinkercad for past simple models or modifications, but that certainly wouldn’t work with this project. My first attempt on the LED openings was to take the round holes and close them and put the rectangle openings into them. I managed that and made a prototype print of that for fit etc. I learned a bit with that and what I needed to make more adjustments with. I had to make the openings a little larger to accept the LEDs, also even then a bit of filing was done to the final print. The LCD wouldn’t quite line up with the LCD opening. The later “final” print I managed to move the LEDs stacked to the left edge like I wanted to start with. They were a bit easier to fit, but still took a little filing of the openings, it is hard to print a sharp enough corner.

Here you can see the LCD alignment issues a bit.

I enlarged and relocated the LCD opening a bit the alignment wasn’t quite right for my particular LCD. It may not be quite the same for all of these types of LCDs.. I also angled the top edge, as the depth that the LCD sets back made it so that I would have made it even taller making it odd to look strait on at. The other change I made to the face was cut a slot into it where the “disk” would have went. I like how that looks better.

I did not use a Pi Hat PCB, so in the back I needed to close the opening and make a circular opening for the DIN socket I used. I did that by adding on to the narrow “center” part of the case. Closing it was fairly easy, making the proper opening then for the Panel Mount DIN socket and screws was done as well. To provide some support when inserting the socket I put a lip on the inside of the top cover. This does not protect the socket when pulling it out though. If I had put the socket in the Top of the case, it may have been stronger but would have been more difficult to work with.

First prototype on the back opening. I didn’t make the “tab” tall enough. I don’t yet have the inner “lip” to help support the socket.

The last part was the bottom of the case. With that I made a change to one of the standoffs, with the Pi3A+ it had a component on the bottom hitting and pushing it off the standoff. I didn’t want to damage my Pi.. I think a Pi3B+ doesn’t have something quite as close to that spot. I closed some of the opening in the bottom where the SD Card opening is, I didn’t want it any more exposed than required, it was only a minor change. The more important change was on the side where the Power, Audio and HDMI ports are. For one I closed the areas up a bit, raising the bottom up, the top down, putting in a bit of a panel at the one place that didn’t have one. I also had to widen them, I couldn’t get my cables in at the ports, and it wasn’t because the openings were shorter now. Maybe some cables are a bit more slim than mine. My final intention was to take some thin plastic something like a transparency and cut the USB, HDMI and audio/video jack out to use as a backer to close the rest of the opening and not block access to the ports to make it a bit cleaner. I haven’t gotten around to that. I did do something like that on my large Pi1541 for the one port in the back.

Here you can see the Pi3A+ installed in the prototype case. There is room for a Pi3B+ but the usb and network ports would not be accessible. Those little blocks on the right side that do not exist in the upper center part are areas I added some material on the bottom part to make the openings look a bit neater to me.

For the inside I did go with hand wiring everything using some protoboard. The front control panel being fairly easy to do, short of alignment of the LCD. The buttons as designed work great, it is an great design.

Here you see the back of the control board in the front. The LCD and 5 buttons are on the front side.

For the Pi1541, well I make what I call an Option B+SRQ design for the Pi1541.. This is Steven’s Option B plus another Level converter and wiring up the SRQ lines. I will have to update this post with the schematic. You can find the schematic though that I used on my Pi1541 + Bare Tapduino project. Just note that one includes a Tapduino in addition to the Pi1541 section. I can’t find an Option B+ wring diagram, it has been unfortunately rather vague on how the later additions to the Pi1541 are wired up. For my reference I did modify the Option B wiring diagram to be a Option B+ but as I didn’t make the original diagram I won’t post the modified one. The SRQ is required for the high speed emulation of the later Commodore drives with the 128 I think.

I don’t believe my schematic is the best to follow. I think a Wiring Diagram is generally easier for someone to follow. The schematic below is from my Pi1541 + Tapuino The SV2 header goes to the Pi to various pins. I am sorry it is not the best to follow.

To make the main Pi1541 board section, I used another piece of protoboard with my required IC and two level shifters. Also the filter capacitor and resistors etc. Everything connects back to this board, then this board goes off to the Pi3A+.

Here is the start of the main interface board. It had a lot to add yet.

Below is the completed electronics. The White 3d printed parts were the final parts I made. The front being the LED placement, LCD Opening and Slot changes. The middle ring with the back tab at the proper length. The interface board is mounted with the two screws that hold the middle ring in place as well.

Below are pictures of the completed Pi1541.

Final front. There are some 3d printing minor defects.

Here you can see the LCD Alignment is much better that the prototype.

The port in the back with the tab height corrected, it also has the supporting inner lip on the top cover. Still with the yellow bottom. Then the odd bonus of seeing the Pi LED in the back.

The side view with the yellow bottom. The USB and HDMI are just a bit narrow. Yes the PLA case is a bit translucent.

Might as well have the top view too. Yes that is my Pi1541 schematic in the background.

I figured I would do some size comparisons to my other 1541 drives.

Here is my 1541ii drive with it. I used the same Green and Yellow LEDs. I have seen other 1541ii with different colored LEDs though?

Here it is my 1541, and my Pi1541 + Tapuino. It is far more compact.

Does it work? Yep.

I have printed a white bottom for the drive and installed it. The difference being the color and slightly wider openings for the USB and HDMI ports. Over all this Pi1541ii design should be easy for someone to build for the most part. With a Pi1541 Hat that fits the alignment of the original case, just print the original center part without the tab added. It can accept a Pi3B+ as well as the A+ just fine. Then the only bit to custom build is the front panel board, sure a pcb could be designed for that to even make that easy.

If anyone wants the modified 3d models I should be able to get them to you. If there is interest, I would probably look into the option to post them as a modified design on Thingiverse. I have never looked into that though and do not know what is involved. I don’t think the support rim on the top cover should get in the way of the Din plugs in the back if they line up properly. The main modifications were the tigher fit on the bottom, as well as the changes on the front of the case.

You can check out the Pi1541 site for the basics and the wiring diagram for the Option B design. It is just adding the SRQ lines with another level shifter, I tend to label it as “Option B+” or “Option B + SRQ”. There are people making pi1541 hats that include the SRQ lines, but I have seen no official diagrams posts, they are just doing it the way I am not that I am the first to do it. The SRQ I believe is needed for the 1581 Commodore 128 high speed transfers. All of the required pins are labeled on the GPIO header in that diagram. There are what I call the Option B Plus Pi Hats out there for sale. That is why I don’t understand why there has been no Option B Plus wiring diagram posted.. You can also now use a Rotary Encoder to replace the UP/Down and Select buttons. I like the idea of the Rotary Encoder, but it didn’t fit the case design. For my Pi1541 + Tapuino I did use a two way toggle switch for the Up/Down controls to eliminate a button. I might have used a Rotary Encoder on it had that been an option at the time, as I could have used it to replace 3 of the buttons (Rotary Encoders have rotate left, rotate right, and have a button that you can press them in).

https://cbm-pi1541.firebaseapp.com/

Commodore 64 GAL PLA Replacement

Back in March, Adrian at Adrian’s Digital Basement posted a video (and a later follow up) on a cheap PLA replacement made with some still accessible GAL chips. When I saw it I picked up 5 of the required GAL chips. You need two chips to make a PLA replacement from them. The actual chips are GAL20V8B chips, preferably the -25LP but with an alternate programing of the one chip you can use the faster -15LP chips instead. The chips can be programmed by downloading the .jed files from the Daniel’s project website: https://www.freepascal.org/~daniel/c64pla/

While the GAL20V8B chips are no longer manufactured, they are in Daniel’s words still rather easy to get and cheap. The chips are able to be programmed in the popular TL866 programmers. I have the newer TL866ii Plus that I purchased for programming EPROMs. There are the older TL866 programmers and those work too, which is why he choose that model of chip rather than a similar still in production chip. This indicates that if someone wanted to they could likely recreate this project with that still in production chip at some point, but unless there is a shortage on these chips I doubt it will happen.

I happen to look around for parts and projects, so I had the chips laying around, but I have never pulled the trigger and ordered any manufactured PCBs from any of the providers out there. If you read my other posts you will see I have designed a couple of my own and etched them at home. That is a lot of work. These premade designs are not meant for that level of prototype work, the tolerances are too tight for me to make the way I made my other ones. Double sided and very small traces, a lot of through holes that need plated etc.. My one design being a single sided board, with wider gaps on the traces, also the lack of solder mask. The other design being wider gaps yet between traces to help with the lack of solder mask and it is difficult to manually align both sides and get them transferred to the board properly. I also designed my double sided board specifically to having to use vias between the sides.

So, how did I come about making progress after eight months? Well in looking for some parts for my TI99/4a, I found the PCBs for the GAL PLA for sale at what I felt was a reasonable price and ordered two. It turned out to be a very easy project. Since it is a manufactured board, all it really amounted to was installing the pin headers for everything. Adrian used Machined Sockets for the GALs and Machined Pin headers for the legs, in my case I used Machined Pin Headers for everything. Beyond that I did the same thing as he had.

Keep in mind what order you want to solder the headers up. If you use sockets, then you must put the underside legs on first. If you use all Pin Headers like I did, I found it easiest to put on the inner pin headers for the GALs on the top side, then the lower “legs” and finished up with the outer pin headers for the GALs. It turned out great. I certainly do NOT recommend using the larger square pin headers.. They damage sockets badly as they are far to large. The “turned pin”/”machine/machined pin” headers can be problematic as well especially in old single wipe sockets.

The Left are “square” pin headers like on Arduino boards, rpi etc. The right though is the machined pin headers

Above you can see the more popular Square Pin Headers. Those are not what should be used for the legs, you should use the Machined Pins instead. These are for the legs, the shorter pins going into the circuit board and soldered on there. The longer legs sticking down and those insert in the IC Sockets on the mainboard.

Machine Pin Sockets. I used these instead of IC Sockets for the GAL chips to insert into.

Above are the Machine Pin Sockets that I used in place of standard IC Sockets. I generally prefer Machine Pin Sockets to the single or double wipe standard ones. They machine type sockets are more flexible than standard sockets as they don’t go all the way into the PCB. These Machine Pin Headers though are almost identical to the Machine Pin IC Sockets, but can be made any required length. I didn’t have sockets of the size of these GAL chips, so I used the header strips. I also used these for the ATMEGA in my Pi1541, as I needed a Machine Pin Socket and the standard double wipe socket wouldn’t work on my homemade pcb.

The bottom with the round Machine Pin Headers.

A side note on the Machine Pin Headers and Machine Pin Sockets that I used. They fit together just like they are made for each other. With a little careful work and some heat shrink on the ends you can make them into inline connections for wiring. Sometimes it is useful like when I make lighting in models and such. They fit fairly well, it is a little like using those DUPONT Male and Female cables that use the “square” pins as seen further above. I think these kind of click in a little more securely, they also make a shorter connector in the end.

Unfortunately, before programing the GALs, I tried to program an EPROM for a cartridge I had assembled. A bit over half way through programming the EPROM the programmer failed, now it says it has a short of VCC problem, and fails the self test on the first VCC test.. That meant I had to order a new TL866ii Plus and wait on it to come in. I wasn’t very happy as I did not get very much use out of the first one even though I had it about a year and a half. I tried downloading the new software and putting on the lasted firmware, but the same result.. I have mostly given up on that programmer, but I certainly will keep it around incase I have an issue with the new one, or find a solution on repairing it.

The new programmer arrived the other day, and since I had the latest software and all the files already, it didn’t take long to program up the GALs. Still out of the 5 GALs two of them didn’t want to program successfully. I did program a pair then used the fifth one to start another set. I cleaned the legs on one of the two that didn’t want to program initially and it seemed to program properly that time around. I should have the chips ready to go for a second replacement if I need it in the future. I haven’t tried cleaning the other GAL and programming it again, I can’t do anything with just 1 GAL anyway at this point, but I did keep it incase I can get it working. I generally don’t do much during the week as far as pulling the Commodore apart, so I didn’t test it until today.

GAL PLA Replacement installed. I like Sharpie Oil Paint Markers for marking stuff like this. Standard Sharpie fades or rubs off over time..

Here it is installed in one of my Commodore 64s. If you read my other posts on this one where I cleaned up and repaired it, you may know I have a PLAnkton PLA in it normally. I am just testing this one. The board has a Machined Socket installed in it already which properly accepts the Machined Pin Headers, which the PLAnkton also uses. The PLA in my other Commodore 64 is also socketed, but it has a the factory single wipe socket. Installing the round Machined Pin Headers into that may damage the socket which wasn’t a great quality when it was new 40 years ago. That Commodore 64 still has an original working PLA in it, if I damage the socket it may not make good contact. If the PLA had failed, I wouldn’t be so concerned. In this case I am just testing that it works, so I know it is ready to go if needed. I doubt the PLAnkton will fail me anytime soon, but the factory PLA in the other 64 may.

I also have an ARM SID in this Commodore, I found the SID that was in this one had an issue. It may have been damaged all along, or it may have been when some traces were shorted by the unclipped legs on it.. The original SID was directly installed into the mainboard, and the legs were never trimmed at the factory. That left them sticking through quite a bit, and having the board sitting on the workbench ended up folding them over onto traces, and cut into the solder mask causing a short. The ARM SID wasn’t cheap, but I felt it was the best replacement if I wanted full function SID in the board. I am quite happy with it, but I do need to get the firmware update installed which fixes some issues.

I did not do exhaustive testing of the GAL PLA, but I did some testing here with the Dead Test and a short run of the Diag cartridge without the harness before that. I let the Dead Test run 8 full cycles without any issues.

I certainly like how easy this worked out. It looks well modified, but fits very well and is nicely built. I don’t have Super Zaxxon or anything to really stress this out that I know of. I have reinstalled my PLAnkton and closed the ole girl up. The GAL PLA is going to be packed safely in some EDS conductive foam for a rainy day.

Below is a link for Adrian’s first video on the GAL PLA. He did a follow up testing the Epyx Fast load as well.

Thanks for reading. I hope something here is helpful. I do most of these posts to kind of pull together different sources and include little things that I came across in doing these projects that may not have been mentioned in the other source material that I had when doing the project. This was a quick and easy project even though I kind of started thinking about it quite a while ago.

Due to getting these boards in and a couple others, I have finally made a customized board that I have ordered from JLCPCB. I know I see a lot more advertisements for PCBWay. Maybe I would try them at some point. JLC seemed more strait forward to get the initial order in and seemed a bit cheaper. Provided those boards work out, I expect that I will be putting together a post on that project after they come in. I have worked on a few things that I haven’t gotten around to posting. Mostly simple stuff that doesn’t take much in the way of a post and may not be of much value to post.

In the end I really don’t like waiting on things, or I may have ordered some of these PCBs myself. Then of course I waited 9 months to find some that someone else went to the trouble to order…. It really showed me how easy it is to put together a simple project like this when you have a properly made PCB compared to trying to wire up some sort of adapter from Pin Headers or IC Sockets and jumper wires. My Pi1541 was very time consuming to build. Sure there was a good bit of planning and construction, but had I ordered in the PCB, it would have been so much easier to assemble. It would have also been a bit easier to design the board when I didn’t have to take into account making VIAs by hand, dealing with lack of solder mask etc.. The Pi1541/Tapuino board did initially have a number of mistakes, and that would have kind of sucked to have ordered in and have to fix that, but it would have been possible. The board is kind of specific too, I didn’t want 4-9 laying around forever.. How many people want a Pi1541 the size of an original 1541 anyways? If I were to redo the project and it turned out possible to design it to be the proper layout and size to be a Pi Hat type but fit the original 1541, as well as maybe a break away Tapuino board section that could be stand alone.. I may have seen a use for more of the boards. That was far beyond ever doing with my hobby level board etching ability. I have since made a second Pi1541 (without a Tapuino), that one was a lot of hand wiring and would have been so much easier with a PCB or two.. Still what am I going to do with 5-10 of a board.. Most of my projects I only need one or two of.

Pi1541 in 1541 Case & Tapuino – Part 3 : Schematics and a bit

I wanted to post the final Schematics for the Pi1541 Option B+SRQ and Bare Tapuino here.

Gerber Files for the board can be downloaded from here:

https://github.com/Markeno76/CommodorePiTap

Below is the Bare Tapuino schematic. It is basically a Tapuino using a bare ATMEGA328 instead of an Arduino Nano etc as the base. The ATMEGA is burned with the Arduino Uno boot loader. It can be programmed by pulling it or on the board. The required connections are available on the board by the Reset pin plus and other headers. That is why the Reset pin is there, to make that easier. I didn’t route a regular ICSP header though. It was hard enough to route this board for me, and I believe the other header with the required pins would have had to been unplugged for it to succeed. There has not been any firmware update for the Tapuino in a good while either. The design is a combination of the schematics from the Tapuino Github. The C2CON header is for the secondary Cassette for recording from it. I did not use that, although I do have the header in there on my board I have no connector anywhere to accomplish it. Because I am not using that feature, I really don’t need the 4052N on my board. That is what it is for. The 4052N can be bypassed by putting two jumpers in its place. The first jumper goes from Pin1 to Pin3 on it (Write Signal). The second bypass jumper goes from Pin12 to Pin13 (Read Signal). The Tapuino is a Tapuino 1.5 plus the Read and Write LEDs from the Tapuino Mini 1.02, and then using a bare Atmega instead of a Arduino Nano or Mini etc. I could not find schematics for the later Tapuino versions, I guess someone else made them to sell and has not released them. I didn’t care for a buzzer or speaker attached to hear the playback, so I was fine without that. I really do not have the Read or Write LEDs on my board at this time as they were added later. I might add them, but I am not sure it is worth the trouble. I would have to take my control panel apart to get them installed, my thought is to place some surface mount LEDs just behind the mesh. The other thing I would like is there was another firmware out there that had some “graphical” look to the Tapuino LCD display, I would really prefer that. I can’t find it anywhere, it was posted on a German blog I believe, but only pictures of it, no code etc.

The other note on the 4052N is that the 74HTC4052N does not work, but a 74HC4052N does work on the Tapuino.

Being a “Bareduino” base, there are other components on the schematic that are not typically on a Tapuino. That is because most are based on using one of the Arduino boards as a base. It was a good excuse for me to make a Bareduino.. I figured why waste an Arduino Nano or something like that if I was making a board anyways.

Pi5141 Option B + SRQ and TFT LCD Passthrough header.

The above is the Pi1541 Schematic. It is Option B plus with the addition of including the SRQ signals. They will be required for some updates to the firmware to take advantage of.

The TFT LCD Passthrough is probably less useful to most, it is actually a traditional Mini Din PS/2 Port. That is what my little 7″ Composite LCD came with as a connector. I decided to put it into the Tapuino. It was originally for use on my workbench to test my Commodore 64. It supports 2 inputs, the default is the one connected to the Pi’s Composite video output. The second input is out the back of the 1541 case and can be connected to the Commodore 64 Composite Video output. The board footprint and setup is actually setup so as to allow putting a Second Serial Din port side by side with the first one. If that was the case, then the TFTLCD header would be wired over to the back of the Serial port and the Serial Din would be installed instead of the PS/2 style Mini Din.

The 7″ LCD though lets me use this device as a stand alone device with the Pi, or with the Commodore as a reasonably portable LCD. There is also a jack on the back of the 1541 for an Audio Input with a switch beside it. If the switch is flipped toward the jack it will output the audio from the external jack to the internal amp and speakers, if it is switched the away from it then the audio is connected to the Pi’s audio output instead. This lets me play the Pi sounds through the internal speakers. The speakers are actually Mono, the rear jack is mono too. The Pi audio output is mixed down to mono with a resistor to prevent them back feeding into each other and damaging the Pi’s audio output. The alternate is that I can again connect up the Commodore 64’s Audio Output to the internal speakers.

The MicroSD Cards are both accessible from the front, the one on the left being the Pi’s card slot, which is extended with a MicroSD extender. The one on the right being the Tapuino’s card. This lets me remove them to add or remove files easily. The other thing it allows me is to swap the card in the Pi. I can then use the Pi for more things like running Raspbian on it, I can then output that to the internal speaker and the 7″ LCD. It can alternately access the HDMI Port on the side of the case (again with an extension going to the Pi itself). I can also put in a card with RetroPi on it, which again can run on the internal speaker and 7″ LCD or alternately output through the HDMI. I can then connect up controllers to the USB ports that are accessible on the side as well.

There are plenty of variations on the design possible. My point was to reuse this case I couldn’t otherwise make use of due to the failed read write head on the unit. The transformer I had left was for 220Volt input, so that wouldn’t have been of use to me either. I wanted to do something with it that would fit in with my C64, and there was just way to much extra space to not make more use of it. I liked the idea of doing a Bareduino project as well.

The Cassette cable worked out really well to. It is basically wired up as a passthrough Pin 1 to Pin 1 from the Din to the Card Edge connector. The Card Edge end is bolted into a DB15 (Gameport type not HD15 VGA (which is DB9 sized)) shell. I later painted it with a Green “Top” mark and lines and a Red “Bottom” mark so that I know which side should be up. I also inserted a bit of plastic to work as a Key into the slot in the connector. I had done that before and it fell out, so i wanted to have a visible mark as well. The wire is part of a very flexible Cat5 cable (yes old Cat5 not Cat5e) that I came across, I pulled out the extra 2 wires to make it more flexible as well. The ends have some heat shrink on them to build them up slightly and provide some strait relief.

Above you can see both the 7″ LCD and the little OLED on the drive face both display the Pi1541 output. So it can be used with or without the 7″ attached. The Pi controls are there on the left side, the 3 buttons and the 2 way momentary toggle switch. The Red LED is the Pi1541 activity light. The Green led on the left in the factory location is the Pi1541 power LED, it lets you know the Pi’s power is turned on. The other Green LED on the front panel is actually the Power LED for the internal audio amp. The Red tipped knob is the volume control and On/Off for the Audio Amp. The 4 buttons on the right are the Tapuino controls with the small LCD on the right being the Tapuino display. The Tapuino is powered completely by the Commodore 64 Cassette port. So the main power for the Pi does not need to be on for the Tapuino to work. That is partly why there are 2 schematics. There are two 5Volt power sources, the one that Pi uses is the internal Meanwell power supply where the Tapuino section receives the power it uses from the Cassette port, they are not wired together. They do share a common ground, which they share through Serial connection anyways.

I have used this unit for Raspbian as well as Retro Pie as well. My general intention is to use it just as a Pi1541 though most of the time. Originally I figured I would use it for Retro Pie a bit as well, but I have since built a Bartop Arcade to run Retro Pie instead. I really didn’t feel like disconnecting it from the Commodore desk and moving it to the living room to connect to the TV and such just to play some old games (other than Commodore games that is).

I have been thinking of putting a button on GPIO3 for a safe shutdown and startup button for the Pi when using Raspbian or Retropie like I did with my Bartop Arcade build. I just don’t at this time know where I would want to put the physical button. I could reuse one of the Pi1541 buttons, I could assign Safe Shutdown to another GPIO Pin that they happen to already be connected to. Still that would then not work as a wake up button as GPIO3 is the only one that will wake it.

Commodore 128 80 Column RGBI to SCART to HDMI.

I have been wanting to get a working display for the Commodore 128 80 Column mode. Looking into it, certainly get an old compatible CRT Monitor, either a Commodore RGBI monitor or apparently a CGA monitor potentially. Well they are old and they are expensive, and quite expensive to ship. There a couple more modern LCDs, including some NEC Multisync 70 series monitors. They are apparently around, but they are old and somewhat expensive too. If I get a display I would rather have confidence that it will last for a fair while. That and I am pretty cheap I guess.

I looked at options, the Monochrome Composite 80 Column mode is easy. Just make up a cable with the DB9 and a regular RCA plug on the other end. I want color though.

There are some CGA(RGBI) to VGA converters that people make to sell. They convert the Digital CGA signal to an Analog RGB signal, that is close to VGA. The frequency is at the CGA 15khz though instead of 31khz like VGA though. So most monitors don’t accept the 15khz signals (NEC Multisync 70 series is one of the few again, and the 60 series that I have doesn’t). Then you need a second unit that then takes that 15khz to a 31khz VGA signal.

I found a circuit design for a CGA/RGBI to Analog VGA. This is the first part, and you need a secondary converter to take the 15khz signal to the standard VGA 31khz. The GBS-8200 is a popular solution to take the signal to 15khz. I found another solution, which is a SCART to HDMI converter that Adrian Black posted about on his Youtube channel. I picked one up, an a donor cable to make up a proper cable for it.

I took the RGBI converter diagram and came up with a bit of a hybrid of it. I had tried an earlier wiring up to see if my Multisync 60 series monitor worked, it didn’t. So I am making up up circuit I found. There was a report by another site that said they didn’t like that circuit, and preferred another circuit for the process.

The draw back of these RGBI converters is that while they are full 16color output, they output Dark Yellow in place of Brown. It is not a fault of the circuit, it is because that is how CGA/RGBI worked, the Monitors actually handled the color replacement. To do the Dark Yellow to Brown replacement requires including the 74LS138N ic. When it gets the “Dark Yellow” signal, it injects just a little bit into the “Green” pushing the visual output from Dark Yellow to Brown through R1 below.

Update 2/5/23: Today I was looking to revise this project to a PCB Design. In looking at, it I and thought the Sync Invert was incorrect on the schematic. I was wrong, it was correct so I have switched the schematic back to the original from 2019. I have no promise I will complete a PCB design, but if I do I will be posting it up on Github or another site. I am thinking of making the pcb to fit into the same case I used for the prototype if possible. To make it more useful for IBM CGA I plan to put a power jack on it, the Commodore AV Port will be a pin header row or something, so it will be optional. There will be the optional Audio Jack coming from the Commodore AV Port, as well as an option for the Monochrome 80 Column Composite output (because I can), Commodore 40 Column Composite as well as Commodore 40 Column SVideo output. I am making the PCB Design in KiCad at this point. I want to see how that works. I had used Eagle back at the time of making this project initially. I have recently used EasyEDA as part of the Super Game Boy project, as Joe had build it in there. I wanted to see how KiCad compares. The schematic is nearly finished in KiCad, but the one in Eagle as seen below looks “neater”. I am finding some issues with KiCad not having footprints I would like to be ready to use, but we will see once I start having to work them out and find parts.

Progress on the 2023 PCB Design. See my other posts on the progress there. V1.3 files are now released, see “Part 4” post for the links.

https://hobbytronics.home.blog/2023/02/07/commodore-128-80-column-or-cga-rgbi-to-rgba-15khz-vga-adapter-part-2/

https://hobbytronics.home.blog/2023/02/27/commodore-128-80-column-rgbi-cga-to-rgb-analog-adapter-part-3/

https://hobbytronics.home.blog/2023/03/12/commodore-128-rgbi-cga-to-analog-rgb-part-4-a-new-case/

Here are some pictures of the unit built up on some protoboard and reusing a section of board with a HD15 VGA connector on it. There are a couple of things I will be doing with the board, first I will be installing a 150 Ohm resistor on the board (R9). Currently in the second picture you can see an old 150 Ohm resistor in there for testing. I was making sure that 150 Ohms wasn’t too much and that it brings the current usage down to what I consider should be a safer level. Initially I had been using a higher value resistor and the circuit wouldn’t work. The SCART box needs enough voltage on Pin16 “Blanking” which switches it over from Composite Video to RGB Video mode. With too low a resistor I wasn’t happy with the current draw. I am going to be powering this board from the Commodore 128’s AV Port. I didn’t want to risk damaging the computer by pulling to much power through the port. With the 150 Ohm it had lowered it to a better level. The other changes I will be making also involve the AV Port connector. I want to be able to connect up for both 80 and 40 Column video modes, with the AV Port plugged into the box for power, I can’t get to the 40 Column signals. I am going to add another RCA jack for the Composite Video, I will also add a SVideo port somehow later on, so that will be an option for 40 Column mode. The a RCA port was the Audio out coming in from the AV Port originally when the first pictures were taken (in the end I moved the Audio to the side, and made that port 40 Column Composite Video). The Audio also goes into the “vga” jack and is sent to the SCART converter to go into the HDMI signal from it. I could have hard wired in the SCART Cable instead of including the VGA port. I wanted to give myself other options with the box though. That is also why there are some jumpers on the schematic. They are there on the board, but they are not easy to see as they are a bit under the wires in the pictures below. The jumpers can allow to switch from Combined Sync mode (CSync), to the VGA Split Sync (HSync & VSync). The second Jumper is the Inverter jumper for CSync/HSync line, with it one way the CSync is inverted, with it the other way it is not inverted. This gives options to potentially connect to other devices, like the GBS8200, maybe some Multi Sync VGA monitor if I come across one. The only concern I have with either of them, is that I am sending Audio to the VGA port to Pin 4. If the Monitor or the GBS board do anything with Pin4 they could damage the SID or be damaged themselves. The other alteration on the VGA pin out is Pin 9 has the “Blanking” voltage wired into it, old VGA cards (very old I guess) sometimes had a 5Volt output on that pin, so as I am feeding it with something under 5Volts it shouldn’t do anything, but that doesn’t mean something won’t be wired to it. I have seen diagrams of people thinking Pin 9 on the VGA port should be Grounded, which that would be bad.. certainly it wouldn’t be a good thing to do.

So after a lot of checking of my wiring, I finally connected it up to the Commodore 128, and well it worked. That was great because I couldn’t get it to work 100% on the breadboard. I though the issue might be the variation of the XOR Gate IC I was using, so I had ordered in some replacements, so it was either that or all of the slop of the breadboard wiring. There is that “Saturn’s Rings” looking interference there going across centered around the Light Blue line. That was a visible thing on the display. I didn’t have that specific issue in the breadboard circuit. The point to point wiring isn’t the best either, so maybe that has something to do with it. I have yet to try it on another monitor though. Still I am pretty happy with it, and soon I will be able to close the box up and make use of the 80 Column mode when I want to. The color correction on the Brown seems to be working, the text at the top is in “brown”. At the least I can say it looks closer to Brown than Dark Yellow to me. The other colors look reasonable to me as well.

Below here is the SCART to HDMI Converter I am using. I found it on a video by Adrian Black where he was recommending this model specifically over the other similar priced models. He said that Heatsinks needed applied to the two chips inside though.

Below you can see the two heatsinks I installed. I hope they are enough, the little one in the lower right is fine, but the main chip heatsink is smaller than the one Adrian was using. I don’t know how hot these get with use. If they “sort of work” without them, I would hope that they will be just fine with these. They are the type that come with some 3m tape applied.

Above I have put together a diagram of the Output of the circuit I built and how it is wired to the VGA port and then how that wires over to the SCART Cable. For a GBS8200 or proper Multi Sync VGA monitor you would just use a regular VGA Cable. I would feel better if you used a minimal VGA cable, which is R,G,B, Ground, C Sync/H Sync and V Sync. I find that the thin modern VGA cables now only have those wires in them. I have had older ones that were about as small but did have all of the wires in them. I am putting in a jumper to disconnect the Audio from the VGA port for safety. When the jumper is moved to the other position the audio then goes to the RCA port on the side (the Red one not the Yellow one).

Here is the Analog RGB side. The RCA port there is now wired to the
Commodore AV Port Composite Video (40 column output). I painted it yellow to reflect what it is.

Here is a top view once it was finished. The Additional RCA on the side is now wired to the Audio Out from the SID via the Commodore AV port and is Red to reflect it is an Audio port. Below you will see an additional “jumper” that is not on the schematic labeled “<Audio” that is a 2 position jumper that either passes the Audio to the “VGA” port or to the Red RCA Port depending on the position it is set to.

Above I put on text for the 4 jumper locations and functions. SCART blanking is connected or disonnected, Audio is to the VGA Pin4 or to the Side RCA. Then CSync Inverter or non inverting. Finally CSync or HSync (such as if I had a compatible MultiSync Vga Monitor)

I certainly look forward to using this setup for my Commodore 128. I added the label below, it is printed on an inkjet printer with standard paper. I then used some tape to mask off the top of the box, and sprayed it with Locktite Spray Adhesive 200 Middleweight bonding spray. I let it slightly dry before putting the paper inplace so that it would not bleed into the paper. It is sticking perfectly, I guess I will see how long it holds up. I may have put some clear packing tape over it before cutting it out, but I didn’t have any. I have used the process for some cartridge labels as well.

A few References:

https://sites.google.com/site/h2obsession/CBM/C128/rgbi-to-scart

https://sites.google.com/site/h2obsession/CBM/C128/rgbi-to-vga/ultimate

https://groups.google.com/forum/#!msg/comp.sys.cbm/ARbaCb8n9Sg/B0UPWvrKOaUJ

Nothing above is exactly what I ended up with, but that is what I based my converter off of. I used H2Obesssion’s CSync and SCART info, and then the other for the Digital to Analog and Brown fix. I would really have liked H2Obession’s “Ultimate” circuit to have worked out. There were reasons it did not work in my case, mostly I think it was the SCART Blanking. If I make another, I was thinking of trying it again.

The unit does work for me, it may not startup the Sync signal quickly enough and I have to reset the Commodore 128 to get the display to show.

The design can be adapted for IBM CGA use. The only difference there is the source of the 5Volt power as there is no Commodore AV port to supply it. Certainly a DC power jack could be added instead for a 5Volt DC power input.

The Computer Saver (C64 Saver)

Ray Carlsen created a protection circuit for the 5Volt DC line on the Commodore 64 computers, as well it can be used for other Commodore computers and other units that use a 5Volt DC input. The Commodore 64 power supplies supply both an unregulated 9Volts AC and a regulated 5Volts DC supply. The old 5Volt Regulators tend to fail and just quit regulating, causing the full power to goto the Commodore Computer, which can’t handle more than 5.5V input. When at 5.5Volts that is the maximum voltage the Commodore 64 Ram chips are designed to handle. The circuit is designed to cut power to the computer if the power goes to 5.4Volts or higher. Ray custom selects his components to get the proper fixed trip point.

Console5.com sells a kit that includes the components to build one of these circuits. Ray Carlsen also sells his as built calibrated units. The one thing is that the 5.4Volt cut off wouldn’t be ensured suing the Console5 kit. Ray mentions adding some additional resistors to fine tune it when building the circuit. I don’t know how far off it may be without doing the tuning. I took Console5’s diagram and compared it to Ray’s. Ray had since added a capacitor on the one transistor as well as a 220k resistor that were not on his schematics. With that information I decided to come up with a circuit board design using Console5’s kit that I picked up. I was able to find the Relay footprint in Eagle. I could not find the Fuse footprint though. I ended up modifying a footprint from a 20mm fuse to match up the 15mm version to. I think I got that right.

Here is the revised schematic. C1 is the added capacitor. R8 is the added 220k Resistor. I have replaced R6 with a multi-turn trimpot in the diagram, it is for fine tuning the calibration of the trip point to 5.4 Volts. This is NOT the exact diagram that was used for the prototype circuit board in the pictures.

Here is the revised circuit board layout. It has C1 and R8 as well as the Trimpot for the voltage adjustment. Below in the pictures you will see C1 is present, R8 is not, and instead of the trimpot I have paired some spots for regular resistors.

After coming up with what I hope to be a proper layout. I started to try to make the board. I had been on the lookout for a potential printer to use for Toner Transfer PCB work. I came across a HP LaserJet P2015dn. It was quite dirty, and the toner was low, but it was printing. I had been tossing around the idea of buying a new cheap laser printer, and I am glad I didn’t as I was looking at a Brother laser printer and they apparently can’t be used for toner transfer due to the higher melting temperature of their toner.

So I started off cutting down a piece of circuit board material.

Here I scored a line with a utility knife and square.

This board is a piece I picked up back over 20 years ago at school. It was old stock then.. It is very thick and very strong fiberglass based board.

After first marking it, I put it in my vice and scored the back side a little as well as the front deeper.

Here I folded it back. I was a bit impatient, and it was a very hard and high quality board. It took a good bit to snap it off.

After breaking the thin strip off I cut that down in half again. Then I sanded the surface to get any tarnish off. Any tarnish will prevent etching, or mess with it atleast. It can also make the toner not attach properly. Then I cleaned it with some IPA to get any residue off as well as any oils that may prevent the toner transfer.

Next I then split it down in half length wise as well. That was a bit easier. I then sanded the surface down to remove any oxidation. I then used a bit of 91% IPA to clean any oils.

Next I taped the cut out print to the board.

Here is wrapped the board with the print out.

Here you see the back side. No this is not the copper side.

Here we see the final result. Well I knew the toner was low and the printout very light. Due to that fact I was quite happy to get as good as I did. I wasn’t seeing any distortions, or smearing the toner. I was really testing if I could do it at all with the toner and iron. A trick to using the Iron is you aren’t trying to make the iron as hot as you can. You are trying to make it hot enough, but not so that it completely liqufies the toner. When it does that it smears it around and bleeds etc. So the other thing is that pressure has alot to do with it. I picked up a small sturdy iron ( I hope it is sturdy, it looks to be) that I could put a lot of weight on.

Well it didn’t work out. The toner was too low in the printer mostly.

Since that went pretty well overall considering the toner level. I figured I would risk a new toner for this very old HP Laserjet. I picked up a cheap aftermarket one, it worked and was better than the empty one, but the toner is not quite 100%. I also tried printing on a glossy magazine page. Both worked great, the print was great, very dark and clear. The paper took the toner well.

Here I started over with a new toner cartridge. This time using a glossy page from a magazine instead of the expensive toner transfer paper.

I prepared the other sample board, again sanding to polish it clean and IPA to clean it. I then cut out and wrapped the board wit the print out. There you can see the setting I used on the iron, a little past half way. I had read about iron temps, and used an ir thermometer to check the temp of the iron to get something close to what was recommended in a post I was reading over. I have a piece of old mdf or some fiber board there, then a smooth light blue painted aluminum plate that I placed on my workbench to iron the board with. First I let the iron heat up, then I set it on the board for a minute. I then put as much of my full weight on the iron for about 30 seconds (per the instructions I was following). I then applied heat and pressure to the board moving the iron around for another minute and a half or so. Then the board was placed in a bowl of cold water to get the magazine paper to break down to be easy to remove without pealing off the toner. I found the magazine paper to remove very easily, the expensive toner transfer paper doesn’t do that. You can see the first board and this second test here as well. The main issue I had was keeping the board from sliding around. I have some silicon thimbles (well that is what they look like), and put one on a finger to help me hold it without burning myself too much. The silicon does help alot, but doesn’t stop all of the heat so be careful. I actually use them when soldering, they also help with the heat there, but there you also can still get too much heat through if you aren’t careful.

Here is the little iron I picked up for this usage. It is small, which may be a problem with a bigger board. But I can put a lot of pressure on it with it’s design.

Here on the top you can see the new board. It came out almost perfect from what I could tell. Only about 3 minutes to transfer this design was great.

Now that new top board looks much better. There were two nicks in the print, the one on the outer marker line on the top and that little spec on the ground plane around the middle of the bottom. The spec was missing from the printout as seen above though.

My method of etching a board is based on a post I read about using Peroxide, Vinegar and a bit of Salt. I have this stuff around, it seems to likely be safer than other methods. Cleanup is easy. It is slower. I doesn’t see how it is as fast as the author said, but it does seem to work. 2 to 3 ratio of Peroxide and Vinegar, plus a fair measure of salt (enough to keep the solution green instead of blue). When it goes blue it will pretty much stop, but if the salt is added and it goes green that pulls out some of the copper from being reabsorbed into the solution basically. This is a very small board, and I have a nearly full ground plane, so the solution didn’t change color, at least that I could see in the dark here. Yes I etch it outside for safety and I don’t know what fumes come off of it if they may corrode other metal nearby. Here yo can see the reaction and that yes the copper went green from it.

Here is the board after I took it out. Just a little before I took it out, I scrubbed it with an old toothbrush and some of the toner started to come off. I could see a trace with some copper in the area that needed removed, so I put it in for a short time anyways. The copper is fairly thick on this board, and it was only a tiny bit longer. It did cause tarnish in those exposed areas.

Here is the etched board, you can see where the toner started to fail. Real HP Toner may have held up a little better.

Here is the board after cleaning with some acetone and then a light sanding again to remove the bulk of the tarnish. What is left should not hurt anything. I will inspect the board that everything is etched enough and no shorts are there. You can see that little gap at the bottom on the outline. That was that little bit that didn’t transfer. I did touch up the other mark on the top where that spec was missing with a Sharpie before etching.

Some areas do look pretty close, but it is late and I am going to get some sleep. I will be looking at this tomorrow hopefully. Then if any bridges are found I will see about clearing them up and drilling the holes for the components. I am afraid solder bridging will be an issue. Those gaps between the traces are not that big. The picture above looks to be a bout double size to the real thing when compared on my monitor. It might not be the most fun to solder. If I had made the gaps wider, it may have been hard to keep a good ground path to everything, but I could see if that could be tweaked a bit. Still I only have 1 kit here and I don’t see why I would be etching another.

If anyone wants a copy of the design let me know. The custom thing is the library that has the fuse holder on it.. I don’t know how to to share that out. I guess I could put the board files on Github or something?

Console5 Kit: https://console5.com/store/commodore-64-power-saver-circuit-kit.html

Ray Carlsen’s pages: http://personalpages.tds.net/~rcarlsen/cbm/c64/SAVER/

Toner Transfer Post: http://www.robotroom.com/Toner-Transfer-Etching-2.html

Etching Post: https://www.instructables.com/id/Is-the-best-PCB-etchant-in-every-kitchen-/

Of course after I finished the board, I found Ray had added a 220k Resistor (R8 which is on the revised layout and schematic). Well I will see about adding it in, but for my current board it would be a bodge wiring bit to get it in there for this initial test board.

I decided I had so much time in this board, and it was close enough that I could still build it and see what I came up with.

First I checked for any shorts across any of the traces, and everything checked out there. Next I moved on to using the Drill Press to put in the holes. There are several sizes of holes, all quite small. The largest size, for the Fuse Holder and Relay did fit in my drill press, although it nearly didn’t get tight. The next couple smaller sizes wouldn’t get gripped by my drill press. So I took the bottom off of my metal Pinvise Drill and put it in the chuck, I left the other size piece inside it to provide some extra support to help reduce the chances I would crush the tube. I tried to put just enough pressure on it to keep it from slipping as to help reduce the chances of damaging my pin vice. It did work out, and there was no real damage to it in the end thankfully.

Here it is completed, the mounting holes are a bit too close to the circuit though. You can see there are several sizes of holes.

Next I tinned all the copper and used some solder wick to grab up any bridged areas. Then I retested for shorts and corrected one created by the solder. I next went on to test fix the Fuse Holder and Relay, they fit perfectly. I removed them and started soldering in the lowest components first. That was the Zener Diode and the other Diode. Next I worked on the Standup resistors, transistors and capacitor. Then I did the four 2pin headers, the input, output and two LEDs. I don’t want the LEDs on the board. I did not set them up as Pin Headers though, so while the holes were properly spaced being 3mm LED pads, the holes were too small. I do have some “pin type” header pins, that on the bottom side are smaller round pins and not square the whole way through. I used those. Finally once everything else was installed I went on and did the Fuse Holder and the Relay. As I went I kept checking for solder bridges, and it was a bit of an issue without the solder mask as I expected. My next board I will see about leaving a larger gap on the ground plane.

Bottom side finished. It was not the easiest to work with a board like this with such close traces it liked to get solder bridges a lot.

Here is the top side completed. You can see the two points for the adjusting resistors. I need those too as it is flipping way to early.

So I tested it out and it it throwing at 4.76Volts. That is way to early. I was concerned with the resistor values being matched at 470Ohms when Ray’s was not matching resistors. That and Ray’s mention to have those secondary ones to help adjust it. Changing the one would change the trip point up and changing the other the trip point down. In reality the two will both go both ways, if the one is set higher then it will push it one way then if it is lower it will go the other way. I guess having both makes it more flexible based on what it needed to get it right to the 5.4Volt trip point using common resistor values. So I will work on that later to get it tuned in and see what it takes.

After further testing, I found it about impossible to get the trip point set with the resistor values on hand. I resorted to using a mini potentiometer, that let me set the trip point. I put it in the circuit at R6. After doing that I found that the trip point wasn’t remaining stable. I took a long break from it as I was quite disappointed in it. I have finally went back to look at the circuit again. I had someone ask about a C64 power supply, and well I happen to need to build a second supply myself for another C64 I have since purchased and repaired. So tonight I revisited this circuit.

I did some more searching on the circuit, and found a Github project with a board design for the Saver Circuit. “OpenC64Saver”. Looking at it, it is Ray’s diagram with the 220k and the capacitor included. The only change they made seems to be swapping the one resistor for a multi turn trimpot like I had ended up wanting to do. Although my board only fit a single turn mini pot on it. I like the layout, but I don’t have Kicad loaded to be able to look at the board design except their rendering. The footprint seems to be the same footprint as the Console 5 kit includes. The resistor values are different I believe, and a few other components. It could be a good start though to get one of those boards and the Console 5 kit.

https://github.com/SukkoPera/OpenC64Saver

So I looked at my prototype again. It was still being unstable. I got to thinking, I wonder if putting a load on the output would help? By adding a small load to the output (150Ohm Resistor, should be about 36mA so not much of a load), it has apparently fixed the stability issues. I have had it running for over half an hour now and it started out set to 5.41V as the trip point, now after being warmed up, it is occasionally tripping at 5.38V but so far solid on at 5.37V. I say that is close enough to being 5.4V trip and being stable. Granted I wouldn’t use this board as built, the single turn pot can accidentally slip or get changed without warning, maybe even by dropping or such.. So I would want at least to have a multi-turn in there instead. I am also not certain that the traces on the board are heavy enough to handle the current required to power the c64 and any cartridges or other items that may be plugged into it. They possibly are, but I think if I were to use this, I would want to make up a new board with the revised layout at the top of this post, or just make the OpenC64Saver board.

Commodore 64 Breadbin #2 Referb : 326298 Part 4 Finish up.

So I had to look into the keyboard issue with the * key. When opening the keyboard quickly get the shift lock desoldered. I have heard people tend to melt and ruin the switches. I had no issues with this one twice though I was very quick with removal and re soldering it. While I was in there I pulled out the two reworked plungers.

Above is the * key pressed, it is showing about 1.6k right there, but it varied above 2k, and if pressed really hard, it went down to around 700 Ohms. When pressed very hard it did register enough to work (sometimes).

Here is an example of another key that was working. around 125 Ohms with an easy press. I desoldered the Shift lock key, quickly as mentioned above, get it heated, and pull the wires and get the heat off of it. Then the removal of the screws again as before. Looking at the board and the plungers, I found the * key plunger had all kinds of white specks of dust of some type on it. I cleaned it off as best I could. The other keys didn’t seem to have the issue. I swapped that plunger over to the “British Pound” key, as I don’t expect to use that key much. I then installed the two replacements I had one going to the * key. I reassembled and then did the test on the * key again, and this time I got 70 Ohms, so that new plunger is working pretty good. I then reconnected it to the Commodore 64 and tested it. The keys were working, the “British Pound” key wasn’t as responsive as the rest, so the conductive pad on it must not be in the best condition, so it was good I moved it.

I did the “Soft press Restore” fix as well. The Capacitor Kit I purchased from Console5.com includes a replacement Capacitor for C38. From the site ” includes a 4.7nF capacitor for C38. Exchanging the factory 51pF for this 4.7nF capacitor returns soft-touch function to the RESTORE key. “

I had not intially put it in, I didn’t know what that modifcation did actually. So I looked it up, and it appears to be a good idea to have. Without the fix, the Restore key needs to be pressed hard and fast to get it to register. This is because the way the circuit wired to it works, it is not looking for a press, it is looking for a specific change that is a bit more digital. So it can miss a simple press, the hard press causing the switch in the button to “bounce” a number of times and one of those bounces tends to then register with the computer. It is a simple enough fix to do. That was the last bit I needed to do inside the case.

Next I put the keyboard back in the case, and installed the new plates and reinstalled the LED.

It turned out looking much better than it did originally. It is painted, so I will see how well that wears on it over time. The new badges look very good, they are thicker than the factory ones. The factory ones are about flush with the ridges around them, these are up out of the ridges a little bit. It is the special Gold remade badges. I think it looks neat, I guess it could have been about as good with the standard badges.

Below here is my stock 64. It has yellowed/browned a little bit, but it doesn’t look too bad to me. The new paint is lighter than the other unit, and I think it overall is a little light, but it is a fairly good match I think.

Well I now have the two working C64s. I guess I will need to make a second power supply sometime. I have the parts for it except the case at this time. I guess it is time to move on to another project.

I would love to hear it if anyone knows anything about the 8Pin Video mod that this had received in the past. If there is any information out there as to how it was done. Certainly removing the original port, drilling for the new one. Cutting a few traces around it to separate the additional pins. Then there are the 2 wires that were added in. I am wondering if there would be anything else involved. I think there were probably two changes in the VIC II area, but I don’t know if they are related or not. I also wonder why this board doesn’t have R36, when I have seen others that do, and a few other changes. There seem to be a lot of variations, and I wonder if some of them are recommended fixes done by the service centers to fix issues with the systems, or make them more reliable?

After finally putting it together, I noticed the power LED had quit working. The lead broke off the bottom of the LED, so I ended up replacing it with another vintage used Red LED from my parts bin. Thankfully it looks the same as the original even when lit up. A new modern Red LED would have likely been a fair bit brighter.

There is a note that the Reset Circuit relation to the 556 IC is different on this specific model of board. The schematics are not correct for it, unless there are correct ones somewhere that I have yet to find. This means that the Reset button on cartridges like the Final Cartridge iii etc don’t work. As well as on the User and Serial ports etc. I may look into modifying the board so that will work. I want to do it in such as way that I don’t have to cut traces on the board though. That is why R36 is missing, it is normally the pull up resistor on the Reset line, where in this setup it is not used and only the 556 is.

Commodore 64 Breadbin #2 Referb : 326298 Part 3 Recap & abit

I had mentioned the video fix for this board in Part 1, but I don’t believe I went over it beyond mentioning. So here it is, Ray Carlsen recommended resistor change for improved Video. These boards shipped with an incorrect resistor installed in the VIC II area, that reduces the level of the Composite Video output.

https://portcommodore.com/rcarlsen/cbm/c64/SCHEMATICS/326298/early%20board%20weak%20video.txt

The resistor is R10 next to the VIC chip. His recommended fix is to add another resistor across the factory installed one. By doing this with the right value of resistor, you can get it set to the proper value. It is easier and safer to pull the resistor and replace it. Anytime you desolder a component you risk damage to the rather delicate circuit board traces. It can be done to look very neat as well.

You should be able to see the “stacked’ blue resistor overtop of the factory installed R10. This combination reduces the value to what it should have been. That did noticeably improve the video output. The factory resistor is 300 Ohms, the resistor that should be there is 120 Ohms. So obviously the signal is reduced. When putting a 220 Ohm resistor across the 300 that takes the value of the two resistors together to to give you around 127 Ohms, so that should be plenty close to the 120 that should be there.

So I managed to replace all of the electrolytic capacitors this C64. The Modulator was quite a pain this time around. Also due to that, I let my desoldering iron sit on idle hot for too long. The tip on it started to break down, so I will have to get a replacement. It worked well enough to finish the job though.

I know some people say replace the capacitors, some people say don’t mess with them if it is working correctly.

I say I hate desoldering the RF Modulator, but as far as something causing something I may see, if the modulator caps are going bad that will affect the video output. The RF Modulator is tied in and affects the Composite output as well, as it usually passes through the modulator. It turns out on this revision though the Composite does not go through the modulator, so it seems on this revision you can possibly just remove the modulator. I haven’t verified that though, and don’t intend to try it at this point.

Above I have prepped to work on the capacitors. They are there, as well as my iron and desoldering iron, and solder collection can that I expel the solder into from the desoldering iron.

As I said the modulator was a pain. They had not “turned” the ears on the modulator to hold it in, they had bent over the small pins. I had to work the modulator loose by getting what I could off and putting pressure on the tab I had loose and hold it down while it cooled, then work my way around. I also ended up pulling the 3 square pins up out through the modulator top. That was my best bet to not lift traces. By heating them with my soldering iron from the top side inside the modulator, until it could put pulled up with my pliers that I was holding the pin with. Once they were out of the way, it was one of those pieces they bent over that was stuck in the end making it so I could remove it. I did loose some of the bottom pads, or do a good bit of damage to them where they can is soldered in with the tabs. In the end it doesn’t look too bad, the one that fell off I put back in place and reapplied solder. The one square pin lost the narrow pad from the bottom, but not the through hole thankfully. It was the audio pin and that is why I decided to just heat and remove them pulling them up out. It was a good idea. They are a tight fit, so once I had them out, I ended up using a small file to file off the old solder so they would fit again. You don’t want them loose, because they are double soldered, you risk the solder loosing contact then.

After getting the modulator off, I replaced the capacitors in it, then went and replaced the remaining ones on the mainboard before reinstalling it.

I cleaned the tabs and such on the modulator body and the holes in the board to make sure it would fit back in easily. After that I reinstalled the cleaned up pins into the modulator. In the picture the center one had some solder on it again as I had started to reinstall it but pulled it back off.

I actually pulled it off, so I could check where the traces went under it, for those three pins. I wanted to be able to make sure they were making good contact before finalizing the work. So I reinstalled it, but I did not solder any of the tabs back tight before testing.

She still worked after the replacements. I haven’t tested the Keyboard or Sound though yet. Yes I was wearing an ESD Wrist Strap and working on my grounded ESD Mat.

After it tested good, I then twisted the tabs on the modulator and soldered all of that back on. I did a bit of cleanup of the flux and reinstalled it into the bottom case. Now I need to do that keyboard work so I can put this all back together and use it again.

The new tips came. I am going to be more careful about leaving it idle when it is not in use.

Here is my desoldering tip. I have seen this happen with Copper based tips, I guess this is Brass looking? If the hot solder is left on them it starts to dissolve the metal of the tip into the solder. It is replaceable, and I like the iron so ordered in a replacement for it. Once they start doing that they keep breaking down. Other types of tips will just burn the plating off and then will quit accepting solder and not transfer the heat properly. I will not leave it idle like that while it is on again. It was while I was working with the modulator, which may have taken a hour. I was taking care to not wreck it, so it took awhile.

Beyond the modulator it was an easy recap. Most of the capacitors I pulled tested pretty reasonable but not all.

Three of the 10uF capacitors tested with almost no capacitance. Otherwise they were a little inconsistent and all of them measured above their stated values. The new ones are closer to their rated values. With those three odd ones, I feel it was worth it.

Well on to revisit the keyboard. I really don’t want to take it apart again, but the * key is kind of important. So I will get that in the next and likely last post on this refurbishment.

Commodore 64 Breadbin #2 Referb : 326298 Part 2 Case Repairs

Well I am getting back to the second Breadbin repair and cleanup as I finished up another couple projects I had put it on hold for.

I did get one of Birt’s C64 Case Saver kits to repair the damage to the case:

https://www.soigeneris.com/commodore-64-caser-saver-repair-kit

I didn’t think I could do much with the tab, and with the two cracked screw standoffs, I figured it was worth while to get it. I will have to say I am very happy with the fit and quality of the parts. I attached them with some JB Well 4400psi Epoxy.

I am doing another coat of paint on the lower portion of the case, partly in hopes of a sturdier finish, but also due to that crack that showed at one of the Din ports in the back. I had glued it, then I used some Epoxy on the inside to help it as well. I then used the White Putty in the crack to help blend it out.

With the top I cut the broken portion of the case tab off. It was the narrow one. I then installed Birt’s replacement tab. It was a perfect fit. Per his recommendation I did slightly round its edges and the two remaining tabs. I also put his parts on to reinforce the cracked screw standoffs in the top. I again used the White Putty on the outside of the crack in the right front corner of the case to help blend it out for the paint. While I had the epoxy, I decided to reinforce the inside of that crack with it as well.

The paint turned out really well. I put on about 3 coats on it. Krylon Fusion All in One Matte River Rock.

I ordered in some reproduction badges for the top of the case. Well I went with the “gold” model type labels. This thing is an odd machine, and the reproduction badges are great, but the way they are made is a bit different so it was not going to look exactly original from close up. So I am happy to make this rather neglected, and somewhat unique 64 look a bit more unique.

I have just finished replacing the electrolytic capacitors on the board. That will be posted in Part 3. The modulator was quite a pain this time around.

I still need to look at the * key and see if I can get it to be more responsive. The two “repaired” plungers are a bit off, the height is just a little wrong. I am going swap them out and keeping them as future spares. I need to open the keyboard to check out the * key anyways, I might as well switch them. I may redo them with epoxy sometime and try to adjust the height a bit more. I don’t know if that will be Part 4 and hopefully end up with it finished up.

Commodore 64 Breadbin #2 Referb : 326298 Part 1

I picked up another Commodore 64 breadbin model. It had a rough time in storage from the looks of it. The system has been in a damp dirty storage area, there were several of them being sold by the same person, in similar conditions along with some other old 80s era computers like Apple ii systems. I guess they were stored in a basement somewhere that had some real water/moisture problems.

As you can see from the outside it is a bit dirty, and some keys were missing. This was I think the second best looking of the batch. Below you can see the inside, the paper shield was a mess, black mildew along the bottom. A good bit of dirt inside. After seeing it in the bag, I decided I wasn’t even opening it inside. So I took it out back and opened it there. I removed the cardboard shield and it went strait to the trash can. The case was then hosed down to get the worst of the dirt off. I wiped the keyboard down a bit and the board before taking them in. The case parts went it the tub and got a really good scrubbing.

I removed the RF Shield and cleaned the board with some 91% IPA. It turns out to be a bit of an interesting board. Yes the screws are mostly rusty, the RF Shield and Cartridge port plate tells a tale of too much water too. On close inspection the board looks ok for the most part, the legs of some of the components are rusted, I clipped a them and the tips just fell off. This board has obviously been worked on in the past. The inner cardboard sheet that was above the bottom RF Shield went strait to the trash, it was about as awful as the upper cardboard shield.. I kind of like this brass looking shield, but without the cardboard to go with it, I won’t be reinstalling it. I don’t care enough to make a new cardboard piece.

You may notice the wires in the above picture. This is a 326298 Rev A board. An early board that only has the 5 Pin Video port. This board was built in 82 based on the unsocketed chips. The board had extensive work done to it. All of the main chips are socketed. They are all dated second half of 84. The 5 Pin Video port was replaced with the later 8 Pin Video port. There are two wires running off from that port, and various cut traces on the top and bottom to separate out the additional pins. I think in the VIC II area there were possibly some other changes. The VIC II area cage was (and still is) rather rusted as well as the RF modulator top plate, and the RF RCA Port was all rusted.

So after the ipa bath I hooked up the board.

It worked, no issues. Next I tested the keyboard, it worked, minus the two broken keys. Some keys were not very responsive though. I did a full teardown of the keyboard to clean it properly.

I first removed all of the keycaps with my keycap puller. I recommend one, they are rather cheap and good insurance to prevent breaking the old plastic. I next desoldered the wires on the ShiftLock key. I had removed the tape from around the keyboard, as you can see, to get to the screws under it. After removing the screws the board lifts off, and you can see the plungers then.

I took out the plungers and put them to the side, then took the keyboard frame and sent it to the tub and some warm very soapy water. I also soaked the keys in the soapy water. Then scrubbed the keyboard and keycaps with a toothbrush and rinsed them well and dried them. I also took the springs which were dirty and some were rather rusty. I put the springs into some White Vinegar. The Vinegar removes the rust, it does make the metal a bit dull looking. I expect if you leave them in too long you may break down the metal too, so I kept checking on them. They cleaned up well, the worst of them you could tell were actually pitted but were still in working order. I then washed the vinegar off with some water and dried the spring as best I could. I placed all of that on a towel to dry properly.

While that was drying, I took some IPA on a qtip and lightly wiped the contacts on the circut board. We don’t want to remove the conductive coating. If you clean too much of it off they keys won’t work. Next I took the plungers, and wiped the shaft part with a damp cloth to get any dirt off, I didn’t wipe the contacts on the plungers, they looked pretty good. They were mostly clean overall due to being covered by the keycaps and in the keyboard frame holes.

All of the good plungers and two broken ones.

Well, I had watched Perifractic’s Lego 64 videos, and I got an idea to try on the broken plungers. They did still work, as I had tested the keyboard with them, they just won’t hold a key now.

So I found a Lego laying around. You see the full piece I started with there in the lower left. I cut it in half, cleaned the plunger up and fited it to it. I shaved it down to go into the plunger shaft a little for more surface area and strength. Then I glued it in with a combination of Bondic and Super Glue gel. I DID have to file down the Lego piece, it was too large and the Commodore Key cap wouldn’t go on it. I used my small Diamond Grit Needle Files from Harbor Freight (they are just small files, I got the Diamond Grit ones, they seemed to work well for me on plastics). I will say that the glue doesn’t hold well, these tops will come off. So it isn’t a great fix, but I think it will work. I am still waiting on replacement Plungers and springs for the keyboard. I put the one plunger back at the British Pound symbol location, but I put the other at another key that is less likely to see much use. The 8 key gets a lot of use.

Here is the keyboard frame after reassembly.

Here is the keyboard back together back in the cleaned upper case. I tested it and it all works. The * key doesn’t work very well though.. When I get the new plungers in, I will probably remove the circuit board again and check that key. I don’t know if it it is the plunger, or dirt, or the contacts on the circuit board. Other than that and the missing caps, the keyboard was quite responsive, better than my other C64. That one I did not remove the board to clean the contacts. Removing to swap the plunger and check that key isn’t too bad. I will only have to desolder the ShiftLock key and remove the screws. The plungers that I am not working with will all stay as long as the keycaps are still on the keys can’t come out.

I does look much better than it did, but it is very streaked. The Power LED plate was actually corroded to the point much of the paint was lifted and flaking off. Corroded Aluminium.. Ya, I guess a good bit of moisture for a long period of time. I plan to get a replacement Badge and maybe a matching Power LED plate, I just don’t know what I want to go with.

Next I started on some preventative maintenance as well as rust removal. I had already removed the rusty tops of the VIC II area and the Modulator top cover. I then desoldered the Cartridge Plate and the VIC II cage which is rather rusty. I did alot of cleanup on the RF Modulator cover and Cartridge plate. A combination of wire brushes, sanding, and polishing with the Dremel etc. To remove the stickers easily, I put a little WD40 on them and let it sit. When I was done they were pretty decent. I tried some Vinegar on the RF Modulator cover, but that removes the protective coating that was still on some areas of it, so I stopped that. I did soak all of the rusty screws (basically every screw in this thing) in the Vinegar to get the rust off. I also removed the Fuse holder pieces, and fuse, they were quite corroded. I placed them into the Vinegar as well (well not the fuse). The Vinegar did clean the corrosion pretty well off the Fuse holder, but it left those areas black, I then polished them back to a shiny surface before reinstalling them. When all the rust was off of the screws and Cartridge plate and RF Modulator cover, I put some “Teflon Non-Stick Dry-Film Lubricant” on them. Not to Lubricate them so much, but to put a protective film on them to help prevent them rusting again. I did the same with the keyboard springs after they were dry. I don’t use the stuff on plastics though it puts a white film on that is hard to remove. So I put it on before putting them in place.

I resoldered the Cartridge Plate back to the board. I also touched up some solder points on the board. The VIC II cage will not be going back in either. I think the VIC will stay cooler without it, and with a proper heatsink installed.

Here is the board reinstalled after cleaning up the rusty bits.

The board was tested again and still worked. So next I installed a few heatsinks.

The 5 Volt Regulator doesn’t have much of a heatsink on it. The Rivet is loose and the heatsink is spinning around. So I decided to remove it and fix that as best I could. I took the heatsink off of it. I placed it on a new 2 Amp capable 5 Volt Regulator, it wasn’t needed, but that is what I keep around. I was a concerned that with the age and heat that Regulator dealt with over the years plus that loose tiny heatsink that it really should be replaced before it fails. When these regulators fail they most often fail open, meaning they will push the full voltage through them instead of dropping it or cutting off the voltage completely.. That fries the ics in the board. I have not heard of them failing inside the C64, while they are the big issue inside the C64 power supplies. With that very tiny heatsink, which was also not making good thermal connection to the regulator I didn’t want to take a chance on it. This time I put a second folded back heatsink behind it with thermal compound between the heatsinks as well as on the back of the regulator and bolted it all together.

This change to the Heatsink is an improvement, I guess. Still it seems very inadequate and gets very very hot.

As far as the case repairs go, I guess I didn’t take any pictures to show that specifically. The top of the case is cracked in the front right corner, it appeared to have taken a hit to that corner. It also has 2 cracks in some of the screw supports. I used my solder iron on a lower temp to melt the inside of the crack in the corner of the case together again. Then I put some liquid Testors Model glue in from the back to smooth it out. That did start to melt the plastic, I removed the excess glue. I have found that if you use that stuff and it melts the plastic and there is too much excess glue the plastic won’t harden again. The one standoff in the top of the care there is cracked as well, I haven’t fixed that yet, I think maybe from the same trauma that cracked the top. Three of the standoffs that hold the keyboard in place were sheared off as well. Those I glue back on with superglue gel. I then clamped them for a day and left it sit. That will give me the best strength, they shouldn’t be stressed while it is curing, which is 24 hours to get to full strength per the manufactures directions that is. The clamping ensures they are down properly and the joint is thin and tight too. After that I put some Bondic glue around them, the Bondic won’t cure in the crack because it needs UV Light to cure. I have also found it doesn’t bond very well compared to Super Glue. It does retain some flexibility and have some hold, I find that can assist Super Glue because it holds so tight, but doesn’t flex and fractures.

This case is badly discolored and I don’t want to try to retrobright it. I picked up some Krylon Fusion All-In-One Paint+Primer “Matte River Rock” paint awhile back to potentially paint a 1541 case. The case had some small chips out of the bottom. I took some Tamiya Putty “white” and filled in and built up the missing areas. It is a potent thin putty that dries quickly, and sands well for me. I it seems to bond to the case plastic well (As the model glue fuses the plastic, so I would expect the model putty to grip it well too). When I was done with the physical repairs to the bottom portion of the case, I put a even coat of the Matte River Rock paint on it. It turned out well. After the paint dried I found a crack show in the center of the half circle of the video port in the middle of the case. I glued that with the Testors Liquid model glue, I hope it holds well. Later I will put on some epoxy to help give that crack a little more support (I should have used Epoxy on the keyboard plungers instead) . I think once the board is reinstalled it will have more support where that crack is as well.

I haven’t done anything to the top of the case so far except weld and glue the one crack. The one case clip on it is broken off and lost. There are also 2 screws posts in the top that are cracked. I have thought about getting one of Birt’s “Hey Birt!” case saver kits to get a new case clip, I could use one of the reinforcement pieces on the cracked stand off, and have spares for the future. As I have to fix that case clip, I don’t want to paint the case yet, I will likely scratch up the paint having it upside down for those repairs. I will put several coats on the case. I want to test the paint on something with a Matt Finish clear over it. Some paints don’t mix well, and can cause the lower paint to lift or got to a crackle like finish. I have found that even with paints from the same company.. So I will test the Krylon Matt Finish first on a scrap of similar plastic (probably a modern computer case bezel). I want to put the clear over it, even though I like the existing Matt Finish of the paint as it should help protect it better.

So for now that is about it for this C64. In the future I will be doing more to it. The remaining repairs to the case. That include the Clip and post repair as well as painting and installing a new Badge plate. Checking out the * key, as well as installing the replacement keys and springs. I also have a capacitor replacement kit for it. With the 84 Breadbin I already worked on, I had found some capacitors that showed evidence of failing, so I figure this one is going to be served well by replacing them. I do wonder if that, especially the ones in the RF Modulator, may make a difference in the video output. I may or may not install some additional heatsinks. The computer is working fine, but it does have bad jailbars, so I may do something with that too at some point. I don’t know of removing the modulator and building up a replacement would help that or not.

I would love to know where the other Breadbins that were sold with this ended up and see that they were properly cared for. There was a very interesting VIC that I would have loved to see, but I wasn’t paying that kind of cash for a VIC let alone one that looked like it spent a few years sitting in water.

Pi1541 in 1541 Case & Tapuino – Part 2 (Board Etching and Build)

Lets see what was left after the last post. There were quite a few changes to the board layout. I found several defects in the circuit diagram I had made.

There were corrections for the Pi1541 section, in that I had connected up one of the signals that I shouldn’t have. The removal of that bit made the design a bit simpler actually.

For the Tapuino side I had several missing connections. So the layout below is not the exact same layout seen below here. This one below is the corrected revision with a few additions as well.

Gerber Files for the board can be downloaded from here:

https://github.com/Markeno76/CommodorePiTap

Here is the design minus the Ground connections.

I built the Pi1541 section based on the Option B design, but with the additional signals wired in that were listed but not wired. That is why I have the second level shifter on the board. I sort of think of it as an Option B+ design, there are some others out there, but most are just plain Option B. It didn’t matter originally, but for some of the new features he has been working on, the additional signals are needed. The problem though was that the oAtn or OUT_ATN should not be wired up as it will never be used, so I had to remove that and I had to do some modifications to my prototype board below. I also added the Buzzer for the Pi1541 to the board design. The next changes were the missing connections to the 4052N on the Tapuino section. I was missing 4 lines going to the IC, two being ground and two to the ATMEGA pins. Some other additions are Read and Write LED Indicators to the Tapuino.

The board I etched was no the above design, to correct my prototype board, I had to cut the lines to the oAtn, removed the wire from the pin on the Pi for as well. I have added wires for the missing traces to the ATMEGA from the 4052 and grounded the other two pins. My buzzer is on the Pi header not the board, and I don’t have the additional Tapuino LEDs.

The images of the board below are the board made with the previous design. That is why it won’t look exactly the same. Some pictures show the corrections and some show how it was originally assembled.

First let us start of with the Toner Transfer process. To do a toner Transfer you need a piece of glossy paper. I initially purchased some Toner Transfer Paper, it was rather pricey for all the more use I get out of it. With Eagle I can not find how to “tile” my printout, so I am using a full sheet for any tiny board.. I found you can use magazine pages, so I tried that. It has worked out pretty well actually, although The first run didn’t. This is a more complex board, it is double sided, and it really is not easy to line it up properly. To do so, I printed out both sides. The top mirrored and the bottom not mirrored (as the bottom is printed mirrored already). I then lay them on top of one another and with light behind them I get them aligned. I then cut the sheets down. This gives me some registration of the alignment. I double and triple check alignment. I tape the two sheets together on two opposite edges with clear tape. I do not want the tape to overlap onto the circuit board material, so I had around a inch boarder around the board printout. If the tape overlaps the design it can make it not transfer properly. We need no assistance in having a failed transfer, that is easy enough to get without additional help.

That being said here is how my first try went.

My next attempt went much better.

With that transfer I just had to touch up some places with a sharpie in the ground plane areas. It was not easy to etch though. It took quite a few passes and pulling the board out as the toner ended up starting to lift in a number of areas. I don’t know if it was my toner (I think it is at least partly the aftermarket cheap toner), or the extended time it was taking in the etching solution for me. I was just using peroxide, vinegar and salt. It was taking a long time. I don’t have anything stronger here, but due to the time it took, I may try to pickup something else in the future.

Below is the completed board after etching compared to my printout samples. There is one bad short, I don’t know why it did that there. There are some areas that were a bit close. The transfer process is to put the board between the printouts, and use heat and pressure to transfer the toner from the magazine paper to the copper. The copper must be very clean and not tarnished. I sanded it with fine sandpaper, then cleaned it with some rubbing alcohol. You want “enough” heat but not too much, too much and the toner melts and deforms, to little and it doesn’t transfer. Too little pressure and it won’t transfer, it seems the more pressure the better. I use a small iron that I can put a lot of pressure on, but I don’t find it easy to do. Once the transfer is done (or you think it is), then put the board into some water. The magazine paper will break down and come off leaving the toner on the board (if it worked). Carefully wipe it off to get that white paper haze off of the surface. Then put the board into the etching solution. (I have some examples and details of the process on my Commodore Computer Saver post, which is a more recent post here.)

I was extremely happy to find out my alignment was nearly perfect. It etched well, although it took forever. This is the second board design I have etched, and only the third board. The first being an adapter board that was extremely simple. The other design I did, I had the traces closer together with less empty gap. The wider gap I had here between traces made it much easier to solder up as there is no solder mask present.

The next step was to drill all of the holes. That took awhile. It required some very small drill bits. I had picked up a set of very small bits from Harbor Freight last year for very little cost. They turned out to be perfect for the job. The only problem is it would have been forever with my pin vise drill. I went to the drill press (from Harbor Freight as well), and well it couldn’t hold bits this small. Well my pin vise drill is metal, and round if I take the bottom piece off. I carefully installed it into the drill press chuck. I tightened it just enough to hold it and left the other bit holding part inside the shaft of the pin vise to make it stronger.

I then went ahead and drilled out all of the holes. The smallest being the holes for the resistors and capacitors. The last board I did, I drilled some of the holes a bit large, that made it hard to get the leads to solder in with too much gap around them. This time I went with the closest size bit I could. That ended up being about 3 primary sizes, the smallest for the resistors and capacitors, then one for the Dip sockets and finally the pin header and other connectors. With a few larger ones for the mounting points on the PS/2 style socket and board mounting holes.

With this being a double sided board, and no plated through holes I had to pay special attention to assembly. I used Machined DIP Sockets for the ICs, as the top side of the pins can be accessed with them tight to the board, and some of the connections are only on the top of the board. I didn’t have a Machined socket for the ATMEGA, so I used machined strip headers for it taking care to make sure they were standing up strait. I did not assemble this board in the order I would if it had been a manufactured board with proper through holes. Normally I would put in the short stuff first, then the taller stuff later and the tall connectors last. I couldn’t do that, and get to the areas I needed to on the top side.

Dry fit on the left, soldered on the right. Because of the non plated through holes, you see a bit of solder on the top side where I had to solder to the top side. The Pins for the Level Shifters (and the other header pins) were soldered by sliding up the plastic bits to get to where I needed top side soldering. I then slid the plastic back down the pins. The Level Shifters were then soldered on from above.

As I mentioned above there were some changes to the board after I etched it. The above image shows it as it was made initially. Below here is the revised board with the corrections. The removal of one resistor in the Pi1541 area, I also removed the one header by the Serial port due to there having been a short under it I had to remove. I didn’t need that header in there for my exact use. That header would be used if you wanted to put in a Second Serial port like the real 1541 has instead of the PS/2 type port I am using for my 7″ LCD interface. The same header coming off the PS/2 port wires to the removed header above the Serial port to enable it in that case. The cutting of one trace in the Pi1541 area by that resistor on the bottom side of the board. The additional two wires for the Tapuino between the ATMEGA and the 4052, as well as the added. Ground pins connected up to it. Again the below changes don’t need made to the “newest” design. These modifications are due to the earlier defective design I etched this prototype from. If you compare them there are quite a few changes between it and the revised design at the top of this post. This is how the board is in my drive now though. I have the Pi Buzzer for the Pi1541 directly on the GPIO of the Pi. I don’t have the Read and Write Status LEDs for the Tapuino, although I am thinking of adding them. It is worth noting that the pinout for the header that is going over to the Pi’s GPIO is different on this earlier board than the revised board. The changes were to move the Buzzer to the board, but also I swapped the positions of two of the signals to simplify the traces going to the Serial port.

The Silver “Stripe” marks on the top of the board are marks for Pin 1 of the various Headers.

Here I have the board installed into the chassis.

You may wonder about the Black Oval thing in the middle on the right, that is a Ground Loop noise isolator. It is between the Pi’s Audio Jack and the Audio Jack of the Little audio amp at the bottom of the case there. Without it, there is a buzz. I have used a couple of these things now for that kind of isolation. I believe they are essentially a transformer inside, so there is no direct electrical connection between the grounds.

I had mentioned in the last post that there was an issue with the Meanwell power supply needing a 200mA minimum load on the 12Volt rail. My solution to that problem was to install two 100mA rated fans. The one I put on by the little audio amp. The ic on it gets warm at higher volume levels, so I figured it was a good idea. The other fan I put on the top of the case by the Pi to cool it. The fans make very little noise and provide enough load to the power supply to be happy even with the Audio Amp off, which also runs on 12Volts. I don’t believe the fans are are really pulling 100mA, but they are close enough that everything is working well.

Yes the Pi1541 is working.

Here are some shots of the exterior of the Pi1541/Tapuino unit.

The Tapuino section is also working as well. Originally though, I couldn’t get the Tapuino to work with the 4052 installed. So I bypassed the 4052 with some jumpers into the IC socket and I was using it that way for awhile. The 4052 is not needed unless you want to be able to duplicate from another device into it. I put it in the design to have it “complete”. It lets you connect up either a physical Cassette and dub off of it, or another Tapuino (why?). To use it, there is the unused red header there in the Tapuino section that would go to the other device. I eventually came to the conclusion that the likely fault was the specific 4052 IC I was using. I was trying to use some 74HTC4052N ics, and they just wouldn’t work. I ended up ordering some 74HC4052N ics, and those worked perfectly. I try to be careful when ordering in ics, and the fact there are so many similar models it just doesn’t always work out. I don’t know what the difference is in the HTC that it won’t work in the place of the HC chips for this use. For the old 8bit stuff usually you use LS stuff, but these don’t come in LS. If you don’t want to duplicate tapes to the Tapuino, then you really only need to bypass the 4052 with two jumpers, you could even leave out the IC socket and jumper on the board.

I would like to post the board design in some way that it can be downloaded by others that may want to try to use it. I don’t know about making Gerber files though, I could post the Eagle files somewhere and then someone could do Gerber files themselves. Eagle is free for these small designs.