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

From: Philip Lord <>
Date: Fri, 13 May 2011 05:30:53 +0900
Message-id: <>
Hi guys,
It's early here (5:06am), so please excuse the brevity of my message as I'll be going back to bed for a couple more hours after.

I did change out the video SRAM as there were a few left over from the main RAM that were still good. Unfortunately this did not change the problem. Pulling the SRAM completely created a checkerboard effect, but there were diagonal lines strafing through the pattern. I'll test this again because at the time I didn't realize this was a valid testing technique.

Pulling the CG ROM takes the image back to its original state, blocks and lines.

One thing, late last night as I was briefly poking around with the logic probe, there seemed to be many places where I probed that slightly effected the pixel flicker. I didn't do much testing as it seemed a little random and inconsistent. So maybe as Mike mentioned, it could be a power issue. I have the  board out on my desk hooked up to an original spare US PET 2001 transformer. Maybe there is some issue with it being a US version on 100v Japanese power. I think I have a JPN to US power step up converter somewhere, maybe I'll try to find that.

Thanks again


On May 13, 2011, at 4:31 AM, MikeS wrote:

> ----- Original Message ----- From: "MikeS" <>
> To: <>
> Sent: Thursday, May 12, 2011 3:28 PM
> Subject: Re: PET 2001 fix Part 3 - RAM/ROM board etc.
>> Looks like the problem is mostly in the fifth character column; wonder if
>> that's where the horizontal line was originally? 
> D'oh! VERTICAL line of course...
>      Message was sent through the cbm-hackers mailing list

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Received on 2011-05-12 21:00:03

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