Next Steps PET 4032 Board Repair

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	by Bill Degnan - 10/29/2009 08:39
I think first however I will check the voltages to all of the chips and components vs. the schematic. There may be an obvious short that I can detect. It may not be RAM because I recall from experience that on an older PET with socketed RAM we could still boot a computer with some bad RAM in any position except the first few slots, the system simply reports less memory. So, I will id which are the RAM that hold the ROMS and the bottom of memory (0000-1000) and replace them first. I don't think it's video RAM, what I believe we're seeing on the screen in the pic is what appears when you first power on a PET, but is then quickly replaced when the system loads BASIC into memory IIRC. Maybe someone else can confirm this. I also remember that on some PET boards (the 2001-8's) the order of the RAM is different, some of them start from the upper left to lower right, some the exact opposite. My hunch is that the RAM in the first slot is the first RAM in the line, etc. So, I am not going to start in the middle of the board. I think I would only do that if the system was acting flaky, or dying after a few minutes. That's the kind of environmental evidence that would indicate a mid board problem, all easy stuff already checked. Reply

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