RE: Dead PET 2001 with 6550´er

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Hallo Klaus,

> On startup it shows just garbage chars on the screen.

The 20xx and 30xx series always show garbage because they have a TTL-logic
video circuit that works right from the moment you power up the computer.
The garbage you see is the random data in the video-RAMs.

> I suppose the ROMS are dead.

It can be anything: 6502, ROMs, glue-logic etc.

You either must have an analyser or debugger to find the fault in-flight.
Otherwise you are stuck by exchanging the parts one-by-one.

FYI, I face the same problem. But I have the advantage of a second working
PET :)
    ___
   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\
   \___|       http://Ruud.C64.org

 

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