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Thread: PET 2001-32N - Diag works in UD9, but with Kernal it fails to start

  1. #121
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    Quote Originally Posted by dhoelzer View Post
    Let's just say it wasn't pretty and leave it at that. I also have a 2nd degree burn as a related part of the mishap, trying to catch my desoldering gun as it fell. It was a catastrophe without a cat being involved.

  2. #122

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    Some weeks ago I made the comment that I find it much easier to design circuits, event fairly complex circuits, than I do to troubleshoot an existing circuit, especially where there are multiple failed/failing components...

    Surveying the state of this PET board... I'm running the RAM and ROM out of a daughterboard, I switch back and forth between as-designed SRAM video and my own bodged daughter-board that replaces the video RAM with modern SRAM, the fact that I've now replaced 14 of the original ICs on this board, and being at a point where I really have no idea what's wrong with this thing, how crazy is this recurring thought that I might be better off 1) hiring one of you to fix this thing or 2) taking the schematics, making some design changes (SRAM rather than DRAM, simplifying all of that to a single 16 bit bus to one chip), modifying the video circuit to output composite directly, possibly evening building a separate on-board VGA driving either an 80 or a 40 column text-only display from modern dual-ported video SRAM (I have two 32k dual ported SRAMs right here, infact), but retaining the original cassette, IEEE488, etc. ports... Do the entire thing as a single dual-layer board out of a foundry in China.. I'd expect the board to cost something like $30-$70 per piece, with likely 200 hours of design time... which is easily how much time I've already invested into everything that I've already straightened out done trouble shooting on (you might remember that my CRT board was a whole *other* adventure).

    What do you all think? Anyone game to be hired to sort this board out? Or should I just muscle through this since I've already put in so much time?

  3. #123
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    I see you have asked for someone to help repair the PET main board in a separate thread.

    Can we just take a breath while we take stock of where you are for a second?

    You state that you have a ROM/RAM card. I assume this is from Tynemouth? If so, what symptoms do you get when you are running the PET with the ROM/RAM out of the Tynemouth card?

    All that you have left on the PET is power supply, clock, video circuitry, IEEE, cassette and keyboard peripherals.

    OK, the existing ROM and/or RAM data buffers could be faulty and a few other gotchas - but you have fundamentally removed a load of 'iffy' logic from your 'need to repair' bucket (so to speak).

    So what happens with the PET configured in this mode?

    If you are quite happy with the PET running like this - then if we can spend a little time getting it fixed in this mode then 'job done'... If it still turns into a marathon, then look for assistance. How does that sound?

    Dave

  4. #124

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    Quote Originally Posted by daver2 View Post
    I see you have asked for someone to help repair the PET main board in a separate thread.

    Can we just take a breath while we take stock of where you are for a second?

    You state that you have a ROM/RAM card. I assume this is from Tynemouth? If so, what symptoms do you get when you are running the PET with the ROM/RAM out of the Tynemouth card?

    All that you have left on the PET is power supply, clock, video circuitry, IEEE, cassette and keyboard peripherals.

    OK, the existing ROM and/or RAM data buffers could be faulty and a few other gotchas - but you have fundamentally removed a load of 'iffy' logic from your 'need to repair' bucket (so to speak).

    So what happens with the PET configured in this mode?

    If you are quite happy with the PET running like this - then if we can spend a little time getting it fixed in this mode then 'job done'... If it still turns into a marathon, then look for assistance. How does that sound?

    Dave
    The daughterboard is actually one of my own design.
    By the way, if you (daver2) can make a version of your test ROM that can work in the 4K space at F000-FFFF I'd be happy to send a new EPROM image to him that can burn on a new EPROM and use that instead of the old pettester.bin.

    Frank

  5. #125
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    Frank,

    I was thinking of doing that anyway. The source code is on my google drive in the spirit of helping out the Commodore PET community. I'll think of a way of conditionally assembling it to maintain a single source file though.

    Dave

  6. #126

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    Quote Originally Posted by daver2 View Post
    Frank,

    I was thinking of doing that anyway. The source code is on my google drive in the spirit of helping out the Commodore PET community. I'll think of a way of conditionally assembling it to maintain a single source file though.

    Dave
    The good thing about 6502 ML is the conditional jumps don't need any relocation. If all JMP/JSR are labeled, you just change .org directive, add the start vector in the RESET vector locations and recompile. I can do that if you link me the source.

    Frank

  7. #127

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    Quote Originally Posted by daver2 View Post
    I see you have asked for someone to help repair the PET main board in a separate thread.

    Can we just take a breath while we take stock of where you are for a second?

    You state that you have a ROM/RAM card. I assume this is from Tynemouth? If so, what symptoms do you get when you are running the PET with the ROM/RAM out of the Tynemouth card?

    All that you have left on the PET is power supply, clock, video circuitry, IEEE, cassette and keyboard peripherals.

    OK, the existing ROM and/or RAM data buffers could be faulty and a few other gotchas - but you have fundamentally removed a load of 'iffy' logic from your 'need to repair' bucket (so to speak).

    So what happens with the PET configured in this mode?

    If you are quite happy with the PET running like this - then if we can spend a little time getting it fixed in this mode then 'job done'... If it still turns into a marathon, then look for assistance. How does that sound?

    Dave
    Hey Dave-

    Actually, the entire last two pages of posts are all with Frank's daughterboard. After install, everything looked fantastic except for the interrupt problem (fast cursor). The longer it ran, the worse it got, getting to the point it's at now. That's *all* with the daughterboard in place.

    To try your ROM, I have it installed and am directing the board to use KERNAL out of the daughterboard and your test ROM out of EDIT. As I stated, it won't even clear the screen.

    I'd very much like to repair this board, but the cascading failures/problems have me a bit frustrated.

  8. #128

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    Quote Originally Posted by dhoelzer View Post
    Yes, sorry, I mis-typed that. I was trying your tester in the EDIT slot with a Kernal in place; it shows about the same screen and fails to start.
    My problem now is that with the typical PETTEST ROM in place of the Kernal, I had been getting screens of Gs and character sets, no problem. It worked every single time. When I replace the PETTEST with the 901465-03 KERNAL ROM, it fails to start. Strangely, it had been mostly starting (COMMODORE, etc.) a few days ago. Now, when I put back in the PETTEST, I'm getting what you see in the photos, which feels like a bad RAM somewhere? Yes? No? Suggestions? Would that cause Dave's TEST ROM fail to run in the KERNAL slot? I wouldn't have thought so.

  9. #129

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    Quote Originally Posted by gatyra View Post
    My problem now is that with the typical PETTEST ROM in place of the Kernal, I had been getting screens of Gs and character sets, no problem. It worked every single time. When I replace the PETTEST with the 901465-03 KERNAL ROM, it fails to start. Strangely, it had been mostly starting (COMMODORE, etc.) a few days ago. Now, when I put back in the PETTEST, I'm getting what you see in the photos, which feels like a bad RAM somewhere? Yes? No? Suggestions? Would that cause Dave's TEST ROM fail to run in the KERNAL slot? I wouldn't have thought so.
    Yes, sorry, I mis-typed that. I was trying your tester in the EDIT slot with a Kernal in place; it shows about the same screen and fails to start.

  10. #130

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    Quote Originally Posted by dhoelzer View Post
    Hey Dave-

    Actually, the entire last two pages of posts are all with Frank's daughterboard. After install, everything looked fantastic except for the interrupt problem (fast cursor). The longer it ran, the worse it got, getting to the point it's at now. That's *all* with the daughterboard in place.

    To try your ROM, I have it installed and am directing the board to use KERNAL out of the daughterboard and your test ROM out of EDIT. As I stated, it won't even clear the screen.

    I'd very much like to repair this board, but the cascading failures/problems have me a bit frustrated.
    Just bumping this thread since it's been silent for a week with no advice.

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