Commodore 64 Black Screen

[HawkMines]

I got a Commodore 64 that only comes up with a black screen. The light comes on, but that's it. Cartridges don't seem to change the problem. I just bought this, so I don't know if the monitor cable will work, or the power cable's bad. I don't own any replacements. What should I do?

[eightbit]

You are going to have to troubleshoot. You do not give a lot of information:

 

1. How is it being connected? You said Monitor? What type of cable and what model monitor?

2. Did you try the RF connection instead?

3. Did you open it, inspect it for missing components/damage and push down on all of the socketed chips to make sure they were seated correctly?

4. Did you test the PSU for proper voltages?

[carlsson]

5. Is it a breadbin model? Then the PLA chip is a strong suspect.

[HawkMines]

1. I only have RF. I would test Monitor, if I had a Monitor Cable.

2. See above.

3. I opened it, and everything looks to be there. Pushed down the socketed chips, same result.

4. Haven't tested the power supply, but the power supply is the only thing I have two of, so I don't think they're both bad.

5 Yes, it's the Breadbin model.

 

I'll get pictures out tonight, in order to clarify what's going on.

Edited September 13, 2017 by HawkMines

[carlsson]

The PLA chip is a kind of memory management chip that naturally runs hot. On the breadbins, it is known for its very high failure rate, certainly the most common chip to break. It will result in a black screen. Some say you can try to kickstart the computer by rapidly power it on-off-on-off-on and leave it in that state, but I don't know how well it actually works.

 

There are a number of PLA replacement solutions of varying degree of functionality, compatibility and price. Some use a fast EPROM (which is considered a bad solution), then you have the various SuperPLA, realPLA, PLAnkton etc. While those cost a little money, they're made from modern technology so they won't break down again.

 

While you're at it, you might want a C64 Saver which is a device put inbetween the power supply and the computer. It will monitor voltages and if either goes bad (in particular the 5V DC may suddenly output 9-12V I think), it will trigger and protect your computer. Commodore's own power supplies are known for having problems with this. You could also look for a modern aftermarket PSU that is safe but it'll be even more costly. All depends how dearly you want to care for this C64.

[xenomorpher]

Getting a power saver is good advice and something I'd get first if you're going to be using an old 1st party power supply and don't want to cause further damage. That could be frustrating when you're trying to troubleshoot.

[Good_Times]

Damn man, this stinks. Even though we both went in knowing full well that the old workhorse was untested, I still feel crummy that it didn't boot right up out of the box. As I mentioned in our private convo, it was always stored properly (to my knowledge) and never mishandled, so it's damned perplexing. Everything looks so well cared for, shiny and nice, wtf ?

 

Although I never really messed with it, favoring consoles & handhelds instead, my parents were always adamant that it was properly treated/stored. Other than the obvious - having a nice Commodore for YOURSELF - it'd sure make my older siblings happy to see it up and running again, I bet. I spoke with one of my sisters about it back when I first listed it here and showed the pics, but all she could tell me was "Oh, the Commodore? It was buried in the garage since the late 80s..." and then went on to reminisce about the great times they'd had with it.

 

Here's hoping that it's a (relatively?) easy fix and that it's able to live on!