Re: PET 2001 fix Part 3 - RAM/ROM board etc.

From: Ethan Dicks <>
Date: Thu, 12 May 2011 13:54:38 -0400
Message-ID: <>
On Thu, May 12, 2011 at 1:21 PM, MikeS <> wrote:
> Have you tried replacing the video RAM?

Besides the fact that I did test (and mark) all the 6550s, bad video
RAM is not likely to cause pixel-level defects in the video... that
tends to be a fault around the chargen and attached shift register or
with the timing chain of flip-flops and such.

I was able to test the SRAMs in another board using a Fluke 9010A (it
plugs into the CPU socket and sees whatever the CPU would see), so I'm
confident that the SRAMs are good.  What I was *not* able to
successfully test with that board was those same SRAMs at $8000-$83FF.
 It looked to me that there was some problem in the path between the
6502 socket and the SRAMs.  This is in addition to any visible
rendering problems.


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Received on 2011-05-12 18:00:25

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