Commodore 64 troubleshooting part 1 the basics - multimeters and alcohol

The first part in a 3 part series covering C64 troubleshooting. Starting out armed with only a multimeter, a toothbrush and some alcohol. We take a look at a healthy C64 and apply what we have learned to a sickly C64 and *spoiler alert* yes, sometimes this is all you need to fix your Commodore 64

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0:00 Intro
1:49 A working example
5:11 Testing PSU voltages
8:20 Testing board voltages
11:33 Temperature and further tests
15:03 Non-working Long-board
19:50 Basic tests
23:38 Testing the switch
27:04 Attempting repairs
29:30 Other potential issues
33:26 Non-working Short-board
35:57 Tracing the fault
40:12 Results
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Thanks for watching!

#commodore64 #c64 #troubleshooting

[davemcd]

Absolute legend. I recently picked up way too many C64s and some other stuff in a bundle and have been stepping through on a first pass test of what there. One today was real rough looking with no signa of life. Googling how to test the voltage rails led me here and with a bit of follow along I could quickly see that the 5V put of the switch was great but the 9V was dodgy. Quick spritz of Iso and it burst back into life and seemingly works better than half the others I tested. Cheers mate, appreciate it greatly, learned some new stuff and have at least one good breadbin now.

[kurtreber]

I've bought 2 separate PSU by now, trying to get my old C64 back to life. Both say they deliver 9v AC but actually deliver 13.5! Am I missing something? Is there a part of the computer that actually gets 13.5v AC and I'm just measuring the wrong part? Could it be that European PSU deliver 13.5v for European C64? I had to buy C64 PSU from Europe as I don't see any available in the US. I did try it anyway, and something starts smoking, so I know something isn't right.

[williammckeever]

Great video. Everyone should always start with the basics before you start replacing chips, etc.

[michaelcarey]

I had a faulty C64 power switch causing all kinds of weird faults. As soon as that 5V rail starts to drop all bets are off. RAM chips are one of the first to flip out with low voltage.

[kyokorn]

Idolo ! man! is great explanation, I recently get my first commodore 64, sadly is not working but your videos is a very effective way to start the troubleshooting, thanks for this!!!

[jandjrandr]

I like the instructions to watch out for the U17 and U18 locations because they can be swapped between the 250425 and 250407 board revisions even though the rest of those boards are very similar. Mixing those up could be disastrous for the PLA, feeding it with 12V. The same applies for accidentally reversing the 6581 or 8580 and those ICs are worth a significant amount these days.

[StripeyType]

There are very few videos which have such high "replay-value" - I definitely imagine watching this several times over!

[moosepig-lcjj]

I'm getting a black screen. I'm getting correct voltages everywhere I can think to check. I replaced the fuse because it was blown. I probed the CPU with a multimeter measuring hertz and got the correct clock output but then probed the VIC and got nothing. The VIC is still getting really hot though. What should I do next?

[markusfritze]

Thanks for this. I think another good idea is to take many many pictures before doing anything (and make sure they are in focus). I would then remove the SID and store it safely before doing anything else – that thing is too expensive to take any risks and the machine works fine without it.

[david.godlewski]

studying for when my two "untested" commodore 64s arrive and I'll inevitably need it.. thank you for these videos!

[Epictronics]

Great video. To avoid breaking the clips on the C64C, I tend to only lift the upper part of the case slightly and then push it forward

[trevorjex]

Thank you for the video, this is going to be super helpful to test out my c64 i just got. Checked the voltages and chips for heat, waiting for the AV cable to come in the mail 🤞

[MrRepeters]

Good video. I love "Deoxit" for switches and sockets. Also, looking for "cold solder joints" for switches and items being pushed or joggled.

[gam]

Great video mate. Do you do C64 repairs? I got one that needs looking at, just don't know who does this in Australia

[konturgestalter]

Just rewatched it. really good. would be great to see more of these troubleshooting tutorials on different devices!

[troytaylor]

I was having problems with getting low voltages on my c64c and I swapped some of the 12v voltage regulator thinking that was the issue but realized I wasn't getting the right voltage into it. Saw this video and cleaned the switch with IPA and presto worked! Thanks for this video!

[brianclimbs]

As an amateur radio operator, I find your disdain for RF shields quite alarming.

[UncleAwesomeRetro]

Very nice video :) I had to subscribe and I am looking forward to the next one.

[moosepig-lcjj]

I'm getting a black screen. I'm getting correct voltages everywhere I can think to check. I replaced the fuse because it was blown. I probed the CPU with a multimeter measuring hertz and got the correct clock output but then probed the VIC and got nothing. The VIC is still getting really hot though. What should I do next?

[koztech]

Thanks for this! Yeah there's a lot of text-based guides, but having a visual guide is extremely beneficial!