I recently picked up this old Samsung SyncMaster LCD TV. With my Retro Computer and Electronics hobby I felt it was worth trying to get working again. It had a paper on saying that it didn’t work, but I tried it anyways and it wouldn’t power on at all. I had come across that it can be possible to fix old lcds due to bad capacitors. I figured it was worth a shot so I brought it home.
The positive to this tv is that it has about any video hookup I may want.
The SCART really interested me as I have made the RGBI to RGB Converter for my Commodore 128 that I setup to use with a SCART to HDMI box. I will possibly be able to connect directly from my RGB unit with the SCART cable I already created. I am not familiar with the Antenna hookup on this TV though, I was initially going to first test this with my Timex Sinclair 1000 as it is an Analog TV, but I don’t have a connector for that port.
So the initial power on test had done nothing already (days ago so yes if it was just powered on the capacitors lkely have a charge and well it can be dangerous to open then). This is also not an LED backlight so it has a High Voltage section in the power supply to power the backlights, so be careful… So I started by opening up the case to see what I would find.
Looking at it I saw 3 obviously bulged capacitors on the power supply board. I looked at the other capacitors and didn’t see any that were an obvious problem. I looked at the control board with it’s surface mount caps all looking fine. I then pulled the board and desoldered the old capacitors. I pulled the 4th one there that was the 820 like the one bulged one as it was suspect because the other one was. I also pulled the next closest one there to the right to check it out.
The 3 bulged ones were bad as well as the other 820 there even though it had not bulged. That fifth one off to the right tested out fine. So I went looking for replacements online, I can get them, and get them rather reasonably from the looks of it. Certainly worth investing in a screen didn’t have anything tied up in.
Still I didn’t want to go spending money on them and have them come in and it not work. So I dug through my spare parts. I found 2 exact replacement 1000uF 10v 105 degree ones. The other two the 820uF 25v ones I didn’t have. Now those two are in parallel, and this was just to test if they were why the TV wouldn’t work, so I went with a single 2200uF 25v capacitor. I don’t recommend it, while it may be just fine even in the long run, this was just to see if it would get the TV working.
So I thought, lets close this for safety 🙂
So I turned it over and plugged it in. As soon as it was plugged in, the power light blinked. I powered it on and it went right to the no longer broad cast Analog TV tuner. Oddly no audio though, I expected to hear static. I couldn’t change the Source either to any of the ports. So I hooked up a Commodore 64 to see what would happen. Below you can see the results.
As soon as I turned on the Commodore 64 I was able to change to the AV Source and it worked fine, the audio was there as well. I still have my S Video cable only at my one desk. I did see what looked like artifacts on the graphics around the shock towers (or what ever those are on the screen upper left). I need to make up a second SVideo cable for my Commodores. I did recently get one in that I want to add to my RGBI to RGB converter for my Commodore 128 80 Column mode.
Now I just need to get in the 820uF capacitors, well I will get a few of the others as well as I don’t know if they will hold up very well and I have to make an order anyways. Just a bit of cleanup and it should be good to go then. I look forward to trying out the SVideo input and seeing if it looks any less artifact like around those towers. I also look forward to seeing if the SCART connector will work with my Commodore 128’s RGBI output for the 80 Column mode.
The new capacitors came in. Below I have marked the ones I replaced. I picked up most of the ones Jameco had available.
So what did I find with them. Well originally those four main ones in the middle there were bad, with the 3 bulged and the 1 that was not bulged. Those were just junk.
The remaining ones I replaced were probably fine. I replaced that one off to the left, as it looked to be the same manufacture as two that had failed. It looked to be perfectly fine. The others that were replaced appeared to be fine as well. I was in there, I had them and I didn’t care to just put the old ones back in.
I did have to substitute some values. The 820uF capacitor value wasn’t available. There were 2 in parallel, so they add up to 1640uF. I ended up replacing them with a 680uF in parallel with a 1000uF to give a capacitance of 1680uF. My understanding is they should preform the same as the 820s would have been. The last three that I replaced were some 330uF capacitors, they checked out fine.
Some Testing with my C64 Mini. The TV doesn’t have HDMI, so I used an adapter to VGA in this case and also connected it to my 12″ bench monitor to compare the output. It works great with that adapter to VGA, but when I tried the DVI port, the image was going off the screen and only washed out and purple looking. I think it may be the adapter box as everything else appears fine. Last night I connected it up to one of my real Commodore 64s via Svideo, and it worked, but was washed out. The cable didn’t have a resistor on it, so that may have been why, I am going to make a second SVideo cable for the Commodore 64 and try it with the resistor on the line there.
I also tested it out with my Composite modded Timex Sinclair 1000 (US Model ZX81) (mod information on another post here). The results were very good. I am quite happy with it. I hope to be able to use this TV for a number of older computers and systems with the connections it has available on it. It is a lot more portable and compact than my Sony 19″ PVM that I have yet to find or build a desk to get it setup.
I decided to hookup my Commodore 128 to the TV as well to test it out. There was some disappointment in that this TV has a SCART connector, and I had made a RGBI to SCART converter that I connect to a SCART to HDMI adapter for using the 80 Column mode (See my other post on that). I was hoping that I could just no use the SCART to HDMI unit and go directly to the SCART input of the TV. Unfortunately the TV doesn’t see the input on the SCART port. This TV detects if a signal is present and then “allows” you to change to that port, if it doesn’t see on you can’t even select the port with the Source or Menu options. So I hooked up the Composite 40 Column mode to the Composite input and used the SCART to HDMI box (with a HDMI to VGA adapter yet) to connect to the RGBI 80 Column mode. The RGBI looks quite good even after all of the conversion. The Composite is not to bad. I do want to see about getting a good picture on the SVideo though. I am going to modify my RGBI to to SCART converter box to break out the SVideo signal as well, as it currently only has a pass through for the Composite video for the C64/40 Column output.
Today my order from Jameco came in. Part of that order included replacement capacitors for the Electrolytic Capacitors in the Timex Sinclair 1000. There are only two in the computer a 22uF 16Volt and a 1uF 16Volt capacitor. I ordered the closest replacements that Jameco had, which was a 22uF 25Volt Aluminum Electrolytic, and a 1uF 25Volt Tantalum Capacitor (which btw are also a form of Electrolytic Capacitor). They didn’t have a 1uF in an Aluminum Electrolytic, but they had the Tantalum which is a valid replacement for it. We specifically want to maintain the microfarad (uF) value, but a higher voltage rating is ok, but try to keep it close as it can have some impact if it gets to far away from the original. Also as the voltage increases typically the size does as well. With other suppliers you can find exact replacements, but I was placing an order with Jameco anyways, and I haven’t ordered from larger shops and also didn’t want the cheap china capacitors. I don’t know for sure Jameco’s are much better, but I hope so.
There is a difference with Tantalum capacitors in while they are Electrolytic capacitors and polarlized, the positive side is what is marked. Where with aluminum electrolytic capacitors the negative is marked. So keep that in mind if you go to swap them. They are more expensive, but I only needed 1 and it wasn’t a big deal.
So I fitted in the new capacitors. With the Tantalum I decided to insulate the one lead there, the positive one in this case. So I used some red wire insulation on it. If you look a these boards, the capacitor pads are doubled, as in there are a few closer points and wider points. The original 1uF was a radial capacitor, so it had long leads like the Tantalum as well, but you can see further to the right the “white” line there with a solder point and a “+” which is the solder point that would be used if it was an axial electrolytic like the 22uF is.
I tested the new and the original capacitors. The 1uF 16Volt came back with 1.114uF 1.1% voltage loss and 2.2 Ohm ESR. The replacement was 1.045uF .2% voltage loss and 2.5 Ohm ESR, so the old one was pretty close to the replacement values. The 22uF 16Volt was a bit different. The old one was 34.1uF 10% voltage loss and 15 Ohms ESR, while the replacement is 20.8uF .9% voltage loss and 0.86 Ohms ESR. I don’t know exactly what I should expect, but my thought is that the 22uF appears to be getting out of specification pretty well.
Once I had the new capacitors installed I did test that the computer booted, which it still did. Then I moved on to the 16k internal ram upgrade, as my 16k Ram expansion does not work, and it is an easy modification to do internally.
With the Timex Sinclair 1000 it is very easy, the computer came with a 2k ram chip already installed in a ram socket. That means I just needed to get a 62256 ram chip which is 32k, but I will only be using 16k of it, and run 4 wires.
You can see the original ram is in the socket, but it does not fill the socket, and is actually not even installed in Pin 1. I am sure many or even most ZX81 computers do not have any socket or may have the smaller footprint socket in place. GadgetUK164’s ZX81 had the two small ram sockets installed on his board, he used some header pins so that he could leave the original smaller socket under the larger ram chip. There may be some that have a smaller socket as well that is missing the top 4 pins, which could be removed and replaced with the full length one, or just clip the pins from another socket or use some header pins like GadgetUK had to extend the socket.
So that I didn’t have to damage the circuit board, I straitened the required pins on the new ram chip.
Next I pulled the 2k ram chip and installed the new chip. The 4 lifted pins are bent up so they won’t make contact with the socket pins.
Above you can see the chip inserted and wired to the board. The wires are attached at D1, D2, D3 and D5 (yes we skip D4). Tynemouth mentions the order doesn’t matter, but they are in that order to be the easiest runs. I used some 30awg solid core wire for this, which also happened to come from Jameco today. I figured it was a pretty color and they are all datalines. I just tacked them to the diode leads. Tynemouth had desoldered the diodes and put the wires through the holes. Diodes don’t like a lot of heat, so soldering to them can risk breaking the diode, but desoldering then resoldering them can too.
The way I did it is not quite as pretty as Tynemouth’s example, but we are talking about a mod that includes straitening pins on an ic and having flying wires on them. The real trick though is doing it the way he had ensures the wire has good contact and won’t have a chance of becoming loose. So I needed to be sure I had good contact and not a bad solder joint that will fall off of the diode lead there and short to something else. I tinned the wires with solder before putting them to the diode, and added a dab of solder to the diode lead. If it was corroded a bit the solder may not take, but it took very nicely and also adding that bit of solder does add some new flux to clean the point. I had my iron set on 300, which is what I typically use for board soldering. I also use leaded solder, which is what these old retro computers had to start with too.
The last bit I did to the Timex 1000 here was to add a heatsink to the ULA chip.
I have now finished the modifcations I had planed for this computer. I just need to wait for the thermal glue to dry on the heatsink before reassembly tomorrow night.
The next thing I need to do is reinstall it in the case. Then I will be testing the original keyboard to see if it is working properly as well as the computer itself. I hope to have this back together tomorrow night and see how it works out.
I got it put together and ran the check posted on the Tynemouth Software post. It shows 32k, but it is showing the 16k Rom plus the 16k Ram.
The keyboard tested out too as fully working. The problem I have is the PAL/NTSC switch (the old channel switch), is offset a bit to far to the edge of the board, and I can’t get it set in the NTSC setting while inside the case. I have to heat the solder and push it to the one side. The holes for the switch were very large, you can see that in my Part 1 post where I have the switch and the cleaned out holes. I should be able to shift it enough to get it where it needs to be due to the side of those holes. A little update, I did shift the switch position and it now lines up perfectly with the bottom case.
I found the heatsink on the voltage regulator had no heatsink compound on it at all. I removed it and added some silver thermal compound and reinstalled it.
After starting to put the system back together it wasn’t working properly. It was an issue with the ULA, if I bumped it then it would get flaky or work. I reseated the chip and then it was working again. I hope it continues to work. I did find someone has made modern replacement ULA chips, hopefully this one will be fine an I won’t have to get one. I have a Samsung LCD TV which I had been working to repair. I finally finished it last night and here is the Timex Sinclair 1000 Composite output on it. It look very good. You can see it beside the C64 Mini there which I was also testing the TV out with. The look kind of cute beside one another. You can find info about the TV repair in another post here.
I think the last thing I should need to do is making up some labels for the case. Where it says “TV” i want to put “AV” or Composite or something. On the bottom where it shows CH2 CH3 I want to make up a new label that shows PAL and NTSC as the options there.
I recently picked up a Timex Sinclair 1000. I first tried connecting it to my LCD TV which does have an analog tuner, but I couldn’t get the signal on it. I then dug out my VCR from the storage area and connected to that. That worked just fine. I am not sure why the TV wouldn’t take it directly. The signal looked pretty good too. I really didn’t care to use the 1000 on the TV all the time though, and not with the VCR all the time either. I went on and looked into a Composite Video modification for it. The modification is done with the same little transistor circuit as the Atari 2600, which I have done before. This is only when the system has the later ULA 2C210E chip such as mine, the earlier ULA 2C184E does not generate quite a standard video signal, so that requires a different circuit. I don’t know if any of the Timex models have the early ULA chip or not. The Timex Sinclair 1000 is a rebranded Sinclair ZX81. The RF Modulator is different for the US Timex model (and the US ZX81 which they did sell some of), there are a few other differences. The Timex 1000 came with 2k of ram rather than 1k like the ZX81 came with and outputs to 60hz NTSC video while the UK model does 50hz PAL video output.
Although in his video he had the OLD ULA chip, and the simple Transistor circuit didn’t work properly for him, he went on to make the more complex circuit later on. His initial bit was using the transistor circuit such as I ended up with.
I found good schematics for the ZX81 here with other useful info. This is where I ended up getting information as to what the various extra Modulator connection labels were.
I would post the schematics and other bits from the sources, but that is their material, this is how i used their material, you would need to build the transistor circuit from TFW8bit, or you can buy the board they sell which would simplify matters.
I went with a little different approach than I initially intended. I was going to leave the RF Modulator in but disconnected, that didn’t work out. There wasn’t much room, and I couldn’t remove the capacitor and resistor(?) and wire from the RCA jack easily, and I couldn’t get the strip board in their easily. In the end I removed the internals of the RF Modulator and installed the new circuit inside.
I want to note that with the ZX81 and the US Timex 1000 (and I guess the ZX81 US kit), the pins used for the RF Modulator are different. I uses the “USA” marked pins, it uses 3 of them.
For the US model, it uses 3 wires instead of 2 for the UK versions. USA3 (Not FR3) is the far left wire, that is apparently the Video in signal although I don’t know where it comes from exactly, as that is not the direct pin from the ULA video output. The next USA2 is actually +5Volts. Then USA1 is the last and it goes down to the Channel 2/3 switch. That switch actually switches between Ground and +5Volts ( I use that later as Tynemouth did).
For the Composite signals, I actually removed the RF Modulator board etc:
Here is the board installed, it is built as TFW8bit’s stripboard, although on a larger piece of board so it would stay solidly in the modulator box.
Above you can see the wires used. Originally the modulator of course used USA3, USA2, and USA1. In this case I am only using USA2, which is now the third wire not the middle one going in. The first is going to FR3, which is actually Ground, yes the modulator chassis is ground as well, but I didn’t care to solder to it, and had the opening for the third wire. The middle wire goes to UK2 which is the video directly from the ULA chip pin, and not the round about way that USA3 apparently gets it.
First I tested this out and it worked great. Here it is via the Composite input on my little LCD monitor I keep on my bench.
There is a second modification though. The channel switch is no longer needed, and it can be re-purposed for something else. Tynemouth used it as a NTSC/PAL switch, which is a simple change. This involves R30, which goes to the one pin on the ULA, and to ground. It is a 10 ohm resistor that when pulling that pin to ground causes the system to operate in NTSC 60hz video mode. When it is disconnected from ground the ULA sets the system to run in PAL 50hz mode. To do this I reused “USA1” which goes to the switch center pin already.
Next the Switch needs a bit of a change. As I mentioned earlier the switch changes USA1 from Ground and +5Volts. We don’t want to wire R30 to +5Volts. To do this you could remove pad from the circuit board, or you could trim the wire from the switch and ensure it was insulated. I didn’t want to alter the board, so I altered the switch.
Next I installed the switch and tested it. Be aware, I made a mistake installing the switch..
So, some may notice I installed the switch to the wrong side of the board. So this won’t work in the case now. Thankfully I realized this shortly after putting all of the tools away, but before I was going to reinstall the board.. So I desoldered the switch again and installed it to the bottom of the board like it should be. When I put the switch on, i reinstalled the old paper label they used to insulate it, and to beef it up a bit, and cover the hole from the old pin that went into the +5Volt pad, I put a little piece of Kapton Tape, you can’t see the tape in the photos though as it is under the original paper label.
I then retested it. I have another bit I am looking to do with this board and that is to put in a 16k ram upgrade on board based on Tynemouth’s post on it, and that again GadgetUK has done a video on. It really is not going to be anything new, while the Composite mod, I did a little differently.
I haven’t tested the keyboard on this unit, I did order in a replacement keyboard for it, and if I don’t need it I will keep the original on it for now. I won’t be reassembling the system though until the ram upgrade is finished. The computer did come with the 16k ram expansion, but the expansion doesn’t work. I had looked at repairing it, and the one capacitor was bad on it, but replacing that did not correct the problem. They are rather complex boards, and while I wouldn’t mind repairing it, I am not sure where to start. I though of stripping out the 74 logic chips to test and such, but that is about all I could do. The internal 16k ram upgrade is quite easy though with the right ram chip and a few wires. I don’t have to damage the board or anything, the Timex came with the socket already installed with the 2k ram chip in it. I just have to pull that and do the few wires onto the new chip.
This is just a little follow up to my C64 power supply post. Since I built that supply I have acquired a second Commodore 64 and I wanted to be able to hook up both. I decided to build a second supply based basically on the same design as the first. You can review the earlier post from the link below:
I used the same case, same Meanwell 5Volt DC Supply, another salvaged IEC power port and switch. With a fuse. This time I didn’t have a spare transformer around so I had to order one. The new transformer is a Jameco 105524 9 Volt power supply. I wasn’t happy that it really didn’t arrive with useful info on what wire was which. I went back to Jameco’s listing for it to look up the wiring, which while the information was there, it was not posted in a clear manner. They have a scanned transformer diagram with 1-6 marked on it, then below it typed text saying what the various wires are by the “colors” of the wires. So go by the wire colors. It turned out that the 4 wires I needed were the same color as the other transformer (which only had 4 wires as it was a 110 to 9.5V only transformer). The new transformer was larger, I guess because of the 230V supply support? It still fit into the case I used previously. I also still mounted the transformer and Meanwell supplies to a piece of raw circuit board material. I did run a ground wire down to the one bolt on the transformer. Still it was grounded already due to the Meanwell case being grounded as well as the copper on the circuit board material.
The thing I still didn’t do that should have been done is grounding the metal screws and metal screen on the top of the case, if the Hot wire every pulled and contacted to the screen that would not be a good thing if it was then touched.
This time I did use crimp terminals on the wires going into the Meanwell screw terminals as I had them around, and I think if they are tight they are a little safer that way.
I again did not include a “Computer Saver” or “C64 Saver” overvoltage protection circuit. With the larger transformer I didn’t have room for sure this time. The Meanwell does have overvoltage protection, but it won’t kick in until well after the damaging 5.4 Volts DC..
The screen is a little smaller this time around, it didn’t need that much of a vent. Really it was just I thought it looked better that way than the larger screen. I put the fuse on the bottom, as having it in the lid, I couldn’t put the nut on it before. The Hot/Line/Live wire goes first to the switch, then the back of the fuse holder from there, then through the fuse back over to the Meanwell supply terminal where the Transformer is also connected to it.
I wanted to do a power led… I forgot to. This thing is very tight, it would take a good bit for me to get the board loose so I could get back at the screw terminals.. I have to take the 5 screws out holding the board down, pull the fuse holder out the back, and feed in some of the output wire cord to lift that end of the board.. I am not wanting to risk pulling any of the rather short wires out of the crimp terminals, or making them loose and dangerous later on. I may go back and do it at some point. I would like them on both supplies. Basically some wires and a resistor to an LED off of the 5Volt output..
Above you see the finished supplies side by side. The metal stickers that I ordered from “marstickers” on Ebay turned out amazing. I believe they sell them on Etsy as well, as I found the listings there, the pricing is similar. That is also who I ordered the reproduction Commodore 64 Gold case badges form for my second C64. These are cut metal foil sticker, mirror finish. They came with a backer and clear top piece that holds them into position to get them placed properly.
A few little things, make sure the supply isn’t a bit under voltage at the connector. If the wire is too long (and possibly to thin), you get some voltage drop on the cable and that can be bad for the operation of the computer. I went with a wire around 4′, but some people go longer. So I get a slight bit over 5Volts (5.1V max) on both of my supplies at the power connector.
The wire I used is virtually the same diameter as the pins. It is stranded security wire, it is not very flexible and doesn’t have many strands in it. It is not perfect, flexing it too much will likely cause it to break. Still it is real copper and is stranded, and a good diameter for the power lines.
The 5Volt 3Amp Meanwell supply should be 15Watts The 9Volt 1.5Amp transformer should be 13.5Watts.
28.5Watts/110Volts = 0.259 Amps. Then the fuse should be rated at 125% of that. So 0.259*1.25=0.3238 Amps for the fuse at 110Volts
28.5Watts/220Volts = 0.1295 Amps. Then 0.1295 * 1.25 = 0.1619 Amps for the fuse at 220Volts
If you figure the Meanwell’s 77% efficiency that should move it to .366 Amps at 110Volts and .183Amps for 220Volts.
You should get the closest Amp fuse that is above the value calculated. Probably 400mA if you can find one at 120Volts or 200mA at 220Volts if that is your voltage there. If the rating is to close, then the inrush surge when plugging in could blow the fuse. You want to use normal (fast) acting fuses not “Slow Blow” fuses.
I am no professional at calculating fuse values. I believe that is correct though. The trick is you are figuring the Wattage usage of the supply at the top safe level of it (at the supplies efficiency level), so that you can then relate that power usage to the 110/220 AC, as that directly translates back to there.
The C64 won’t be drawing 28.5Watts out of the supply ever, unless something is wrong.
The factory supply (output) should be 16.5Watts 5Volt 1.5Amp (7.5Watts) plus 9Volts 1Amp (9Watts). So I expect the C64 won’t end up drawing more than that.
Factory supplies seemed to have 120mA or 200mA fuses on the AC line for 220Volt supplies. That seems to indicate they went with higher numbers, but they had 7805 regulators. With the 7805 to give out 1.5 Amps at 5 Volts actually used 1.5Amps at the input voltage, 9-14Volts probably. So they were using more nearing 21Watts (at 12Volt input) at full load. Well as the load increases the input voltage to the 7805 should in theory drop to close to 9Volts. Figuring that 120mA would be right for 21Watts.
The Meanwell has over voltage protection, I did not include a fuse on the 5Volt DC after it. If you did, you would want a 1.5Amp fuse probably there as the Commodore 64 should not pull that much safely anyways although it may blow before the protection on the Meanwell trips, although the Meanwell may still trip faster than the fuse will blow.
This is just what I did, I have not included any wiring diagrams or detailed parts list. It is a rather simple build really. The Meanwell gets the direct 110Volt AC to it, along with ground. The Transformer gets the same direct110Volt AC. Everything else is sending the right wire to the output on the Din power connector hta goes to the Commodore 64. This same setup could be used for a Commodore 128, swapping in the proper power connector, as the 9Volt AC transformer I used and and the 5Volt Meanwell supply I used can handle the additional current load. While this is a simple supply working with AC mains from the wall outlet isn’t a safe thing to do if you don’t know what you are doing. Like I mentioned above, the metal screen and the metal screws that hold it on SHOULD be wired to Ground for safety, if built into a metal case or having any external metal should be grounded, such as the screw heads. The enclosure’s metal corner screws are electrically isolated so they aren’t a problem in this exact case. I expect if I go back and add the Power LEDs that I will be grounding the metal screens in my case. I have been building supplies off and on for a couple decades and have a few years of electronics training having worked with open chassis and vacuum tube electronics back in school. Doing a supply like this is something you should really look at carefully if you go to make one of your own.
There is a simpler way than to work directly with the AC directly and wiring things up. You can get a good quality 5Volt DC AC Adapter, and if you look carefully you can find some 9 Volt “AC” adapters (often used for older security systems I think, but what for in them I don’t know, but you can still find them). Then you can take an extension cord (even a 2 wire one if both Adapters are 2 prong plugs, be sure it is heavy duty enough though), plug those two adapters into the extension cord and hide that inside an enclosure, cut the cords and wire in a cord with the Din power connector for the C64. Jan Beta had has done just that, it is likely a safer project. Retro Recipes has as well.
I wanted to post the final Schematics for the Pi1541 Option B+SRQ and Bare Tapuino here.
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 the 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 that I have seen are based on using one of the small 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.
The above is the Pi1541 Schematic. It is Option B plus 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.
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.
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 he “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. The 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).
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 Adheasive 200 Middleweight bonding spray. I let it slightly dry before putting the paper down do it wouldn’t 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.
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 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.
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.
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.
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 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 taped the cut out print to the board.
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.
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.
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 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.
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 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?
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.
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.
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.
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.
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. aroub 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.
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, well the modulator caps if they are going bad will affect the video output. The RF Modulator is tied in and affects the Composite output as well. Well that is what they say anyways, I really haven’t looked into it.
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 the can is soldered in with the tabs. In the end it doesn’t look to 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 apparently 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 remain ones before reinstalling it.
I cleaned a the tabs and such on the modulator and the holes in the to 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 I guess. Yes I was wearing my ESD Wrist Strap. The blue mat is a grounded ESD soldering 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. So now I need to do that keyboard work so I can put this all back together and use it again.
Here is my desoldering tip. I see 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 I will see about ordering 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.
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.