Help needed with PET 2001

r.lagendijk_at_hccnet.nl
Date: 2006-06-08 22:21:38 

Hi everybody,

I'm trying to repair an PET 2001-8C. When I turn the PET on it displays a
lot of garbage on the screen. But just on the 3rd quarter of the screen.
It's the same garbage every time.

I switched or tested the TTL's in the video circuit but nothing changes. I
switched the 6550's main RAM with video RAM but also no change.
I switched the 6550 Char ROM with another ROM now there is different
garbage on the screen so the ROM is being read.

I replaced the 6502 but no change. The PET should display without the 6502
running so I did some test without the 6502 installed.

I took some pictures:

http://www.xs4all.nl/~lagendr/Diverse/PET 2001.htm

I reseated all chips that are in sockets. The video circuit chips are now
also in sockets (not the cheap ones.)

Is there anybody who has a idea what's wrong with my PET?

Greetings Richard


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