Thanks for the tips. I have a logic but working scope right now (there's one
up in MN in one of the storage units).
----- Original Message -----
From: "Ethan Dicks" <erd_6502_at_yahoo.com>
To: <cctalk_at_classiccmp.org>
Sent: Friday, October 25, 2002 9:25 AM
Subject: Re: Pet Question
>
> --- Keys <jrkeys_at_concentric.net> wrote:
> > Tried my Pet 2001 series today and no display? If I turn the bright up
> > all the way I can see white broken lines across the screen. The built
> > in cassette players comes on fine. Anyone have clue where to begin?
>
> Do you have an oscilloscope? A logic probe? Knowing what tools you
> have helps direct the assistance.
>
> Check for a reset pulse on the CPU (or any other VLSI chip - it's the same
> signal). Check for clock to the CPU. One of the chips (I think it's
> the 6522) has to work or the video is permanently blanked (i.e., if you
> remove it entirely, the machine runs as best it can, but you'll see
> nothing). If it's nothing that basic, it might be a component fault
> in the video circuit. Since you mention it's a "2001" - that means
> that there is no 6545; the video is in TTL. The schematics are at
> http://www.funet.fi/pub/cbm/schematics/computers/pet/index.html - pick
> the right link for your model (static PET vs DRAM-based-no-CTRC)
>
> Oh... check the voltages first. ISTR there are two +5VDC regulators.
> One failing can cause all sorts of unhappy behavior.
>
> Cheers,
>
> -ethan
>
>
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Received on Fri Oct 25 2002 - 10:17:54 BST