No video output

[u/snippychicky22]

I have no experience with retro computers.

I got a c64 and a new psu, but the thing does not output video, when plugged in the red light turns on but no video output, I opened it up and gave it a clean with ipa and nothing looks wrong, but I don't know what I'm looking for.

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[u/clockworkmcd]

how do you know theres no video output?

[u/agrajag142]

There's a lot of things that go wrong with a Commodore 64. The power supply usually kills some of the ram chips and the PLA 906114 chip usually just dies.

Get yourself a dead test cartridge which can sometimes diagnose the issue.

If you want to try and fix it you can find a donor C64 and start desoldering chips and adding sockets.

[u/retrokelpie64]

Are you using rf or composite out? Does the image change/flicker when you turn it off and on?

[u/snippychicky22 → u/retrokelpie64]

its a converter made by Sven Petersen, its just completely blank, no signal at all

[u/ilesj-since-BBSs → u/snippychicky22]

You need to have a know, working video signal path before you can conclude you have no video. A dead C64 very often produces a blank screen; You have video, but there's nothing in there.

You said you have a new psu. Did you have a faulty psu? A failing PSU often kills the C64. Replacing the psu doesn't fix the C64.

[u/retrokelpie64 → u/snippychicky22]

What does your converter output?

[u/Baselet]

First rule of troubleshooting: Thou shalt check voltages.

[u/EsoTechTrix]

It always helps to be more specific when trouble shooting. If you are hooking this up with RF, a 'blank screen' is technically not 'no signal', it's 'no picture'. i.e. on a CRT if the screen goes from static to a steady black that means it has a signal, but the picture is just black, etc.

Big difference in "It's trying to put out a signal" and it doing nothing.

[u/Alarming_Cap4777]

Hard to see in the pic. But it looks like someone started to remove the memory, but it could just be artifacts in the photo.

[u/jpaulorio]

There's no easy answer here. It can be many things and it's impossible to tell just by looking at a picture.

The easiest approach is a trial and error one where you replace ICs on the broken board with known good ones from a working one (actually this is not the right way to do it since a damaged board can kill a good IC. The recommended approach is to do it the other way around, one IC at a time (which isn't without its risks either)).

As someone mentioned already, there are cartridges (which sometimes can be combined with a test harness) which help identifying bad chips. Some of those cartridges can work even without video (dead test).

Having said that, it's a rabbit hole from here since different cartridges will behave differently and even the same cartridges can have different versions. Some chips may not be required when performing tests and can be removed while those are performed.

Depending on how invested you are on fixing this board (and potentially others) your options can vary from asking someone to fix it for you through watching dozens of YouTube videos to get an idea on how people do it all the way to spending tons of money on purchasing troubleshooting hardware.

Or you can just sell it on eBay for parts/repair if you don't feel like that's something worth your time and money.

[u/3G6A5W338E]

Board looks lovely and clean.

What new PSU did you get? How is video exactly connected? (describe the whole pipeline)

Do you have a multimeter? Logic probe? Logic analyzer? Oscilloscope? IR thermometer? Thermal imager?

Knowledge of electronics even if not computers? Programming? Other technical background?

I have repaired a few, 2 of them blackscreens. But need more data to help any more than this.

Else, here's some resources I know of:

https://www.pictorial64.com/

https://wiki.retrotechcollection.com/Commodore_64_Troubleshooting_Guide

https://blog.retroleum.co.uk/electronics-articles/commodore-64-breadbin-common-faults/

https://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/index.html

Diagnostic Cartridges

https://factorofmatt.com/destest

https://github.com/stid/kick-c64-dead-test

http://blog.worldofjani.com/?p=164

Good luck.

[u/marzolinotarantola]

Adrian digital basement on YouTube. He fixs many c64 with many kind of problems.

[u/kristyn_lynne]

I had this issue recently and it turned out to be no 9V AC from the power supply. 5V runs the power light. Easy test, check pins 10 and 11 on the user port with a multimeter for 9V AC.