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Thread: cbm 8032 rusty and dead

  1. #1

    Default cbm 8032 rusty and dead

    i guys, I need help for a pet 8032 rev 2090.
    it was full of rusty chips and broken tracks, so patiently I removed all the broken chips and repaired the tracks but it still didn't start, black screen and no beep.
    I repaired the reset circuit and it works well since on pin 40 of the CPU it arrives, on 39 there is the clock, I tried with the rom / ram replacement but it doesn't change anything, cpu, ram, eprom, pio e cia, crt are new and functioning, the crt therefore does not start because the cpu does not read the rom and therefore black screen.
    thanks for help
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  2. #2

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    (EDIT: I see you mention Rom/Ram replacement, so you've probably got the Tynemouth card.) There's a card, called Tynemouth Pet Rom/Ram, that plugs into the cpu socket and helps troubleshoot, or entirely replace if you want to leave it in, the memory circuitry. It's a good start. I'd also use one of the USB eprom programmers like the TL866 that can be used to check the logic chips (albeit having to be removed from the board first.)

  3. #3

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    What I do in this case is very tedious: check continuity from every pin in every socket to every other socket and pin that it should connect to.

    But the PET is actually pretty simple so it might be easier to check a lot of other signals first. For instance, are interrupt signals correct? Is the CPU running? If so, what address range is it in?

    There are also ROMs for diagnosing the PET.

  4. #4
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    Default

    Quote Originally Posted by Xchip View Post
    I tried with the rom / ram replacement but it doesn't change anything, cpu, ram, eprom, pio e cia, crt are new and functioning,
    If the RAM/ROM board did not work, then I suspect a fault (open or short) on the data or address lines on the mainboard which will keep the I/O chips from working. A NOP Generator will help when scoping the Address lines for proper square waves, and activity on Data lines. Do you have a scope? The NOP Generator is made from a couple of 40 pin IC sockets.

  5. #5

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    Or can be cobbled together with a few snippets of wire. But the use of sockets is cleaner.

    One of the PIAs could be pulled to make sure it's not holding /IRQ low, but I don't recall which.

  6. #6

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    Do you have an oscilloscope?
    Dwight

  7. #7

  8. #8

    Thumbs up

    ok, I can get an oscilloscope, I put a video of the measurements made with a logic probe, I have already removed all the chips and tested with ic-tester and repaired the short circuit continuity test tracks one by one, ram tested with ram-tester, cpu 6502/6522 tried on a vic20, crt 6545/6520 were purchased new but I can not test it, new eprom tms 2532 programmed for the basic and replaced, 2716 for editors and characters, all new sockets, replaced resistors and new capacitors but funds of warehouse equal to those existing as in the list of components, I did a complete restoration

  9. #9
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    Quote Originally Posted by Xchip View Post
    ok, I can get an oscilloscope, I put a video of the measurements made with a logic probe, I have already removed all the chips and tested with ic-tester and repaired the short circuit continuity test tracks one by one, ram tested with ram-tester, cpu 6502/6522 tried on a vic20, crt 6545/6520 were purchased new but I can not test it, new eprom tms 2532 programmed for the basic and replaced, 2716 for editors and characters, all new sockets, replaced resistors and new capacitors but funds of warehouse equal to those existing as in the list of components, I did a complete restoration
    The video link does not appear to work. With all the work, is the status the same, no beep no screen?

  10. #10

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    yes no beep no screen, i check with oscilloscope and post the video, i'm sorry for error but i don't have experience whit this

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