From: William Levak (wlevak_at_grex.cyberspace.org)
Date: 2006-04-30 03:03:20
On Sat, 29 Apr 2006, Anders Carlsson wrote:
> Hi.
>
> Some of you already know that I today went to pick up a few PETs and
> accessories for the people who made explicit requests. One of the
> machines I picked up was a PET 8296-D, which to me seems like a
> rather all-in-one PET with computer, disk drives and monitor in
> one.
>
> However, unlike all the other machines, this particular one doesn't
> boot properly, which I knew already when I picked it up. I could
> replace with with some other PET, but this was the only one of this
> kind. The question is whether I am able to fix it, or if it even is
> worth shipping it as a broken PET to anyone who would be able to fix
> it up. The symptoms are as following:
>
> The computer chirps at power-on, and both drives power up shortly.
> The red LED in between them goes green. The display shows a scrolling,
> green pattern that doesn't look like character data:
>
> http://www.cbm.sfks.se/pics/8296d.jpg
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. An oscilloscope or logic probe can tell whether this line is
functioning.
If no signal is there, one of those chips could be bad, or one of the
ROM's could be bad.
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