Re: Broken PET 8296-D

From: Anders Carlsson (
Date: 2006-04-30 15:35:27

William Levak wrote:

> You have no horizontal sync.  It is generated by pin 39 on the 6545 and goes 
> through pin 1 to pin 3 of 74LS06 at UD6 and then goes to the video board.

There is a 74LS86 at UD6, but maybe it is functionally equivalent? Anyway,
using my multimeter there seems to be signal from pin 39 on the 6545 to
pin 1 on the UD6 chip, From pin 1 to 3 there seems to be a signal, but
with 1.7 kOhm resistance?

I tried to lift the 324744-01 PLA, but then the computer refused to start.
I also noticed one pin on the character EPROM (yes, this is a localized
machine like all the other PETs) was bent, so I lifted and reseated it,
with no improvement. Maybe pin 24 is not supposed to have contact anyway?

I got ahold of an EPROM burner, but it only takes 2516/2716/2532 chips.
Theoretically, there is a possibilty to find equally old spare chips from
a drawer or other broken PETs, if they are somewhat compatible inbetween
eachother. Of course, we're talking Commodore computers, so maybe I
shouldn't count on that... :-)

Anders Carlsson

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