C16 BLACK SCREEN

[Desperado]

Good morning everyone,
I need to repair this C16, which, when turned on, shows a black screen with three vertical stripes on the right side. I have already checked the voltages, the reset signal, and the clock on pin 1 of the MOS 8501 CPU. I’ve read that the most common failures on this computer are the CPU or the TED. How can I determine which of the two components is faulty?
Thanks

 

[Desperado]

Can someone help me to solve this crazy jigsaw please?

 

[daver2]

Go for the obvious answer (since they are in IC sockets) swap them one at a time with devices that are known to work...

Dave

 

[Desperado]

Go for the obvious answer (since they are in IC sockets) swap them one at a time with devices that are known to work...

Dave

Unfortunately i haven't spare ics for this shameful C16....

 

[daver2]

Buy some...

Dave

 

[falter]

Almost certainly will be either the CPU or TED. And as Dave said the first step is obtaining working spares, which are usually available on ebay, and trying a swap. They were super hard to find before but seem to be in some number right now there.. at least the TED.

 

[ClassicHasClass]

Very likely the TED. In all the 264-type Commodores I've personally found to have blank screens, the TED was at fault.

 

[VintageVic]

You might want to try to source GAL replacement for TED, since the original TEDs have
limited lifespan and are getting rare and possibly expensive. Or build one yourself, if you're up for it.

The PLA16V8, the Commodore 16/116/Plus4 PLA that you can build yourself

 

[Desperado]

You might want to try to source GAL replacement for TED, since the original TEDs have
limited lifespan and are getting rare and possibly expensive. Or build one yourself, if you're up for it.

The PLA16V8, the Commodore 16/116/Plus4 PLA that you can build yourself

Thanks so much! I replaced the 8501 Cpu and now i have a basic screen... Unfortunately i have this screen... I replaced the basic rom but i have always this fault.

 

[daver2]

Can you explain what is wrong?

Is the keyboard working or not (for example)?

What monitor have you got connected?

Dave

 

[ClassicHasClass]

Looks like it's not getting to the READY prompt. I wonder if it's getting hung up in the RAM test.

 

[daver2]

If it is anything like the Commodore PET - faulty RAM in pages 0 and 1 is 'terminal' for normal operation.

Dave

 

[xp0nentz]

This maybe looks like a TED malfunction. Although it can be a CPU malfunction. Try replacing those.

 

[xp0nentz]

Thanks so much! I replaced the 8501 Cpu and now i have a basic screen... Unfortunately i have this screen... I replaced the basic rom but i have always this fault.

didnt see this, Maybe rom or ram.