Samsung 940MW TV Fix No Power

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.

Composite and S Video, and Headphone output. I have the cover plate off but I have it.
DVI, VGA with Audio in, EXT (RGB) on a SCART connector in the US?, And component, some Antennna thing..

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.

Bad Capacitors on the Power Supply Board.

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.

Yep Bad.

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.

Temporary Fix

So I thought, lets close this for safety 🙂

A little bit didn’t fit 🙂

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.

Success 🙂

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.

Timex Sinclair 1000 Part 1: Multi Region Composite Mod

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.

I used Tynemouth Software instructions on the Composite Mod. Found here: http://blog.tynemouthsoftware.co.uk/2016/11/ts1000-multiregion-composite-video-mod.html

I used the stripboard circuit from TheFutureWas8bit Atari 2600 mod:

https://www.thefuturewas8bit.com/2600_comp_mod

I also used info from GadgetUK164’s video: https://youtu.be/5OQuJ-GMwF4

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.

http://fetrmartin.free.fr/ZX81/

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:

Modulator bits, the board, with the 3 wires, and the Capacitor and resistor, and the output wire on the right.

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.

Composite Video circuit.

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.

Success.

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.

USA1 ready to use.
The Grounded side of R30 lifted from the board.

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.

Switch installed properly..

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.

Commodore 64 New Powersupply 2

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:

https://hobbytronics.home.blog/2019/02/11/commodore-64-new-powersupply/

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 new supply. Sorry for the poor picture quality..

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..

Here you see the new supply on the left with fuse holder on the bottom.
Another view of the back and top. The new one is a fraction darker plastic, be great a few shades darker though.
Here is the top front view of the supplies. The new one on the left again. I added the metal sticker I had ordered as well.

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.

Power connector. You can see the wires aren’t tiny compared to the pins, 2 strands are also removed to get them to fit.

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.

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.

This is again the final revised board layout.

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.

Pi5141 Option B + SRQ and TFT LCD Passthrough header.

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.

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.

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.

Success.

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.

Two Heatsinks Installed for reliably.

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.
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 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.

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 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.

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.

Bartop Arcade Build Part 2

This is part 2 of the Arcade. The first post has the Arcade in a good working condition. This will cover some of the final touches.

So I did a bit more work on the Marquee. I did a bit of work on the graphic design. I am in no way a graphic artist. I had downloaded some logos to do the initial graphic. I found some better ones to use and made some other changes to it. I then printed it out on my inkjet printer onto 3 sheets just like the previous test one I did on a black only laser printer. It turned out pretty well, I couldn’t do a full color graphic though. I think I will leave it at this paper graphics for awhile anyways.

For the Marquee there really aren’t any hot spots. I was thinking doing a frosted piece of Plexiglass behind the marquee to handle any hotspots, but that turned out to not be needed (with the paper that is). It is a little brighter than I think I want it, but I didn’t find it too distracting while test playing it. It is quite hard to photograph anywhere near properly though as bright as it is. I have at this point decided to not make a dimmer system for it. I have a couple of workable circuits that I have used for that in the past, I just don’t want to take the time at this point, when the biggest issue is taking photographs of it.

For the LCD I wanted to make a bezel/cover that went over it. To do this I put some 1/8th inch strips up the sides of the cabinet to rest the Plexiglas against. It slides up behind the Marquee bottom board, between it and the top edge of the LCD itself. The strips up the sides are a lot like the ones that were in place on Mike’s build in the video. I wasn’t sure what they were for in his case, they may make it to have very little gap on the sides in his case? He did not cover the monitor with Plexiglas so I am not sure, he also had a small board along the bottom above the control panel, which I omitted due to the Plexiglas. I fitted the Plexiglas so that it just meets up with the back edge of the control panel. It is not held along the bottom and just goes up against the control panel board, so it can flex and make a gap there a bit. I may secure that in some way in the future, but currently it is minimal, and I do not want to make it difficult to remove the control panel if I need to.

Above is the Plexiglas I was cutting for the screen. To cut it, used a board and metal angle. I was cutting from the side on the right side where the knife is laying. Because the Plexiglas had a bad edge from when I purchased it, I needed to be sure to get one good long cut. This stuff is very hard, it is not the softer type. It likes to fracture/crack. I managed to get a very good first cut on the top edge. The next cut, which I was doing in that picture really cracked up the edge. The last cut, cutting it down to the right width, that cut went very well thankfully. I had 1 factory edge and 2 cut edges exposed that turned out pretty well. It was very slightly too wide, to get it down to the right width I used some 180 grit sandpaper and a sanding block to get it just right.

The next part after fitting the Plexiglas was to get it in the final position with the LCD in place and the Control Panel in place. I then used a marker to mark the corners of the LCD behind the Plexiglas. I removed the Plexiglas, and monitor. I placed the monitor on the bench facing up and then placed the Plexiglass back over it using the marks I did while it was in the Cabinet to get a good view and check the marks were correct and centered properly. Once I was sure I had the corners marked that I wanted was to take away the monitor and flip the Plexiglas to the back side. From the back side, I cut into the protective plastic with a fresh Xacto blade around where the monitor will be placed, and removed the outer portion. This left the “monitor area” covered and protected. I also kept the protective layer on the “front” side as well. Then I used some Gloss Black Rustoleum 2x Ultra Cover paint, which is to work on Plastic as well. Painting that on the outer rim that I exposed by removing the film from it. This paint is on the back side of the plastic not the front, I have done this before for other projects. It leaves with a super gloss finish that won’t be touched. The back is not flawless, it is not 100% opaque (with more coats of paint it can be made fully opaque), but it is opaque enough for this use in my case with the single coat. Viewing it from the front the finish is flawless.

Above is the panel after painting it once I removed the protective layer from the inside. This reveals where the monitor will now be behind. The paint does take awhile to dry well. I wanted to make sure it was good and dry before installing it, I didn’t want paint lifting where it meets the strips on the side. The final installation it went well, it is held tightly in place by the monitor at the top edge. I have a fair bit of pressure on the board there from the Monitor to get a little more tilt than the base will give on its own. I was very happy with the result.

Above you can see the thin strips the Plexiglas will rest on. After installing them I painted them gloss black to blend in. You can also see the door latch and spacer block to keep it from moving much. The little block at the bottom of the door is to keep it from going in to far, there is another stop block on the top corner as well, but it is out of view in the picture. The round speaker grills are again easy to see here as well as the chrome volume knob on the right.

Above is the Plexiglas installed with the monitor behind it before I removed the front protective film. Yes those are the wires leading to the front panel, when I reinstalled the panel I wrapped them up so they weren’t such a tangled mess. The monitor is there sitting on the blocking it is screw into the cabinet with. I have some pressure on the marquee bottom support board to get a little more angle out of it, as well as the block is a bit angled itself. I would have used the VESA mount board in the cabinet except this monitor doesn’t support VESA mounting. So there are two screws in the back of the monitor base going into the block there. The block is built up so that the monitor was at the height I was going for, and it is secured to the bottom of the cabinet with 4 brackets with screws. I used brackets as I have it set so that I can get to the screws if I need to remove the monitor rather than gluing it in or putting in screws from the underside.

Above you can see the speakers installed before securing the wiring, the power supply board has been removed, or it would be attached there at the black and red wire, which now lead down to the 5Volt output on the Meanwell power supply below it. The other picture shows more of the internal wiring that goes to the Raspberry Pi, the two front mounted USB ports, the USB power cable which goes to the Meanwell 5Volt output as well. The safe shutdown/power up button wiring is there as well as the speaker input wiring. I ended up plugging the speakers into the Monitor’s Audio Output as I am using HDMI for Audio off of the Pi. If I had plugged into the Pi I would have needed an audio ground loop isolator, because I have the Pi and the Speakers powered by the same power source. I had to do that with my Pi1541, and I had tested on this and had the same issue. Using the Monitor Audio Out that it gets from the HDMI input, lets me eliminate the need for that.

Here is the back with the door latched of course. There is a fair gap at the hinge side, but with the wide hinge that does not show. I should have made it just a little shorter, it rubs easily, but I hope to not have to open it much. I also hope to not loose the keys.. You can see a bit of the run in the paint at the top, but it is on the back and shouldn’t be seen much. Overall I have to say the paint turned out pretty good. There at the top, there is that extra T Molding strip on the Marquee Top. I think it looks nice and provides just a little ventilation due to a narrow gap where the boards come together there, and that little bit of excess still gave me enough with 20′ to do it. The Plug/Fuse/Switch unit in the back there can be wired a few different ways. The one I have has a lighted switch, that switch could be wired either as an Always On light even when turned off, or it can be wired at only to light up when the power is on. I have chosen to wire it so that it will only be lighted if the power is on. Some of them do come with a black switch and those don’t have lights in them. You could just switch the Hot line so that the light would not come on then because if the Neutral isn’t there it won’t light up. With the plug unit, again be certain they are secured well and not loose, a loose wire can cause heat and melting and potentially fire. I nearly soldered used solder and heat shrink on the plug unit for that reason, but I didn’t as then I would have to desolder it to ever remove the plug or power strip.

I had to edit the above picture, as the Marquee keeps washing out almost completely. That is the Marquee that is in it, I just took two pictures and over laid it over the lighter cabinet picture. The Marquee looks a little better in the picture than it looks to look at it. I did not remove the protective plastic from either side of the Marquee Plexiglas yet though. It turns out to be very hard to photograph this cabinet.

Above is the Pi 3B+ as it is sitting in the cabinet currently. I would have taken it out of the case and mounted it to the cabinet, but then I have to rig up a fan to it then. I may do that later. You can see in the picture the wires coming down to the GPIO Pins. The round momentary button on the back of the case there is wired to GPIO3 (Physical Pin 5) and Ground (Physical Pin 6) of the Pi 3B+. GPIO3 is a pin that will by default wake the Pi from a the shutdown/halt condition. Simply editing the /boot/config.txt file and adding the line “dtoverlay=gpio-shutdown” will activate GPIO3 to be a “shutdown” button. You can change the Pin that it will use for the Shutdown by defining the pin in the dtoverlay value. That will then make the other pin be the shutdown pin, but it won’t move the “wake/start” function from GPIO3. The Pi will start the Shutdown process as soon as it has been pressed. Once the Pi has shutdown, you can start it back up by pressing the button again (as long as you are using GPIO3 (Physical Pin5). There are other ways to set this up, they can include a delay where it will make sure the button is held down for a period of time, which could be handy to have. I went with the easiest option though as I have the button on the back where it is not very likely to get bumped while the cabinet is in use. I found the instructions on how to set that up on this thread: https://www.raspberrypi.org/forums/viewtopic.php?t=217442#p1337231

I did do just a little testing firing up one of my old 2600 games. Asteroids, I managed to roll over the score easily. I was playing on the easiest level though. I went back and started with the next level and that did not go so well.

I want player 1 to be the left side, and player 2 to be the right side. I found after reinstalling the control panel that they were backwards. To correct his, I unplugged the joysticks from the USB ports on the Pi and swapped their positions.

The Pi is accessible from the back door if I need access to it. I can also easily remove the control panel. I have two brackets on the back of the Control Panel with screws into to keep it in from coming off. I briefly thought of making the SD Slot accessible on the Pi from the outside like I did with the Pi1541. It is a bit much with 3/4″ material though, and I don’t want the card to be to easy to remove and loose. If I want to add anything to it, I can by using the Wifi connection, or open the back door to pull the card.

The Marquee top has some brackets and screws that I used to secure it towards the cabinet. I want to have it remain removable to easily access the Marquee graphics etc if needed. If I do another cabinet I will likely change the Marquee area. I am thinking of making it set back just slightly then use painted angle metal pieces to hold the Marquee in place. This will mean there would be no T Molding across the Marquee Top and Bottom. It will make it so much easier to install and support the Marquee though. That seems to be how the real Arcade machines did it as well, at least quite a few I have seen. I think I will still use the light box design behind it. That worked great, and the Aluminum will distribute any heat from the LEDs very well. They are using nearly half an amp at 12volts, so there is some heat there, but not a ton over all that rather large area.

So one may ask, about what this project cost to build. In my case I believe that I have a little over $250 wrapped up in materials. I am not counting the Pi 3B+, SD card, Monitor or Power Strip. If those were purchased as well, I would have been looking at around $410. I did not include cost of Wood Glue, Brads, the bit of Aluminum sheet, as those are supplies I had around, as well as the corner blocks which are basically scrap wood. I did purchase a few tools, a 30mm Forster bit, a Router Slot Cutting bit, and the Edge Guide Clamp, those items add up to around another $100. I now have those tools for future projects though.

I have enough MDF, LED strip light, hinge, Plexiglas and a few other bits for a second cabinet. I would need to buy some T Molding, Controls, the Pi, Monitor etc though. I would like to find a better way to cut the Plexiglas, the scoring it with a knife doesn’t work very well on this hard stuff, at least for long cuts. I managed to get it cut, but it could very easily have turned out bad. It really isn’t “Plexiglas” brand that I picked up, I think I have had some softer stuff in the past that was easier to cut, but that wouldn’t hold up for this usage. I don’t remember Lucite cracking like this material has for me, I have used that in the past, it is pretty good stuff, although even more expensive. It has been quite a long time since I worked with it, so I don’t know if it was all that much more fun to work with.

In the end the cabinet is still difficult to photograph, at least with the camera I have. I guess Gloss Black is not much fun for that. Although it is not flawless, I am quite happy with the final result. Above the Plexiglas over the LCD is quite obvious though and gives a good view of how well that turned out for me. The little mix of colors of the buttons is that I purchase a Blue and Yellow set, and already had a white set. I felt mixing the colors gave a better effect.