Commodore 64C Black Screen: See pic

[Boschloo]

I'm getting black screen out of this, can anyone see anything obviously wrong? Already tried re-seating the socketed chips.

It's VERY clean inside.

[hofster]

There is neither power cable or video cable connected...

Seriously, I can't remember ever solving a C64 problem by visual inspection.

[carlsson]

Also if there was something visually wrong, most likely you had even more serious issues than if it "looks" good.

 

Again, I would consult Ray's collected wisdom for a start. Here are his tips for the short board.

https://portcommodore.com/rcarlsen/cbm/c64/c64c-ic.txt

 

[+OLD CS1]

Yeah, black screen can have a multitude of sources: power, bad VIC-II, bad PLA, bad CIA, &c.

[Boschloo]

5 hours ago, carlsson said:

Also if there was something visually wrong, most likely you had even more serious issues than if it "looks" good.

 

Again, I would consult Ray's collected wisdom for a start. Here are his tips for the short board.

https://portcommodore.com/rcarlsen/cbm/c64/c64c-ic.txt

 

This would indicate that my RAM is either bad or shorted. 

I actually bought a can of deoxit but I don't know the right way to use it.

I'm going to put the motherboard in the dishwasher and see if that solves it. That's how I fixed the C128.

[eightbit]

Black screen does not indicate RAM is bad. RAM *could* be bad, but a lot can be bad. I have never had a black screen due to bad RAM on a C64.

 

In my experience black screen has been bad PLA the majority of the time. I of course cannot guarantee that is your situation, but it is a good place to start. 

 

However, this is a crappy short board and it appears almost everything is not socketed at least that I can see from the picture.

 

Where are you obtaining these machines may I ask just out of curiosity?

 

 

And, dishwashers don't fix computers, people fix computers

Edited December 16, 2023 by eightbit

[hofster]

The PLA doesn't fail on the shortboards. It's very reliable.

RAM fails so RAM is a good guess. The ROMs are also failing on these, especially the char ROM in my experience. 

VIC-II is also a common fault.

The dishwasher is not going to be a fix here. It's only a potential recipe for rust.

[Boschloo]

4 hours ago, eightbit said:

Black screen does not indicate RAM is bad.

It's not the black screen that is making me think that, it's the fact that the RAM chips are burning to the touch. So hot that I can't put my finger on it. According to Adrian, this is the RAM 100% of the time.

I tried the Dead Cart in it. Unfortunately I don't have a real Dead Cart so I used the Kung Fu Flash. But the green light on the KFF just kept flashing and Dead Cart never loaded. It works on the functioning C64. 

[carlsson]

Yeah. While the PLA is the most common culprit on older long boards (original breadbin and early C64C models), it is one of the least suspects on newer short boards.

[eightbit]

5 hours ago, Boschloo said:

It's not the black screen that is making me think that, it's the fact that the RAM chips are burning to the touch. So hot that I can't put my finger on it. According to Adrian, this is the RAM 100% of the time.

I tried the Dead Cart in it. Unfortunately I don't have a real Dead Cart so I used the Kung Fu Flash. But the green light on the KFF just kept flashing and Dead Cart never loaded. It works on the functioning C64. 

 

Well, burning hot RAM is a different story. That would certainly indicate bad RAM.

 

As for the PLA, I guess I am unlucky. I have had three short boards over the past 10 or so years with dead PLA's. I wouldn't call any of these (regardless of board revision) very reliable anymore. Especially MOS chips!