Re: Dead PET 2001 with 6550´er

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ruud.baltissen@abp.nl wrote:
> 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.

Yes, except the video sync logic is dead. In Paul Förster's PET 2001, one TTL
that generates the VSYNC was dead, so the video showed only a faint
horizontal line. It seems the VSYNC signal is also needed for the computer
part to start up (IRQ source, IIRC), so this machine also showed the dead
machine symptoms.

Nicolas

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