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Thread: PET 2001 Issues

  1. #1
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    Default PET 2001 Issues

    So I've had my PET for a few months now working fine, although I haven't gotten around to making disks/cassettes for it to run yet, and today I turned it on with a very strange issue (see pictures). Funny thing is I got a PET from my uncle who wanted it fixed up and that has a very similar if not the same issue. I thought it was likely the rom going bad and I was going to pull the chips out of mine and make copies for my uncle's. Both machines are in the 2001 series, not the cash register style but with the later keyboard with the smaller screens, 40 column and 32k ram. If it's not a rom issue then what could it be? and if it is the rom, is there anyone that could write new roms? I was going to try it myself but I have yet to figure out how to set up my programmer.
    20200124_183724_2.jpg20200124_184402_2.jpg20200124_183718_2.jpg

  2. #2

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    Something is generating an interrupt. Might be a 6520 or 6522.
    Dwight

  3. #3
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    Default

    What is the dash number of the kernel ROM D9? Is it 901465-03 (BASIC2) or 901465-22 (BASIC4)?

    Somehow the PET has got itself into the machine language monitor via a subroutine call rather than a break instruction. Is the cursor blinking?
    Last edited by dave_m; January 24th, 2020 at 09:39 PM.

  4. #4
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    Default

    Quote Originally Posted by dave_m View Post
    What is the dash number of the kernel ROM D9? Is it 901465-03 (BASIC2) or 901465-22 (BASIC4)?

    Somehow the PET has got itself into the machine language monitor via a subroutine call rather than a break instruction. Is the cursor blinking?
    I'll check the numbers shortly. The cursor on mine is blinking and I can type, my uncle's isn't flashing and I can't type

  5. #5
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    Default

    Mine apparently has the 03 rom, BASIC2, my uncle's is the other version

  6. #6
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    I am ‘taking a flyer’ here and would say the 6520 PIA at G8 is possibly faulty.

    You could try swapping G8 and B8 over (assuming they are in sockets of course).

    Dave

  7. #7
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    I'm not seeing g8 or b8, would that be ug8 or ub8? Or maybe you're thinking of a different motherboard?

  8. #8
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    Yes, on the schematics the ĎUí is missing. Sometimes I put it on, sometimes I donít...

    They should both be 40 pin devices and both identified as 6520 parts.

    One of the ICs has the DIAGNOSTIC pin wired to it (and the keyboard) whereas the other drives the IEEE 488 port.

    If swapping the two devices over fixes your problem, then you have moved the faulty chip to the IEEE port position and it would need to be replaced.

    If swapping the two devices over makes no difference, it is something else.

    If swapping the two devices over changes the symptoms, one of them may still be faulty - it is just putting it in a different place causes a different fault.

    Dave

    Dave

  9. #9
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    Quote Originally Posted by RadRacer203 View Post
    I'm not seeing g8 or b8, would that be ug8 or ub8? Or maybe you're thinking of a different motherboard?
    Make sure you are using the correct schematics for your version of the PET: http://www.zimmers.net/anonftp/pub/c...01N/index.html . Can you program a 2716 EPROM for a test EPROM in the D8 socket?

  10. #10
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    Good point. 2001, 2001N, ...

    Dave

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