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Thread: Dead Commodore 8032 CBM

  1. #21
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    Excellent, thx Dave.

    Yep, turned power off, replaced one RAM at a time but wasn't checking for monitor flicker (had the hood up), just listening for the 'chirp'. I'll try it again and look at the screen.

    I've tried the DOA 8032's 6502 but no change.

    I'll try those other suggestions over the week (alas work gets in the way) and let you know how I go. Fortunately I have a lot of spare parts (although can't garantee that all the spares are in working order)

    Thx again for you time and commitment to this Dave! I would really love her to come to life again
    "DAVID: Is this a game... or is it real? JOSHUA: What's the difference?" 'Wargames' 1983

  2. #22
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    Quote Originally Posted by Juleshsmith View Post

    I'll try those other suggestions over the week (alas work gets in the way) and let you know how I go.
    Yes it's best to wait until you have enough free time.

  3. #23
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    Hey Dave. Can you only piggyback test RAMs? Can you do that with the VIA chips etc?
    "DAVID: Is this a game... or is it real? JOSHUA: What's the difference?" 'Wargames' 1983

  4. #24
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    Quote Originally Posted by Juleshsmith View Post
    Hey Dave. Can you only piggyback test RAMs? Can you do that with the VIA chips etc?
    Piggybacking is usually attempted with small 14/16 pin parts as you must keep all pins in contact from the top chip to the bottom chip to have any chance. And it only works if an output has failed open and not short. It is just a quick and dirty test, and you look for any change that might indicate things have improved. If so, you replace the part and see if it fixed anything.

    The only reason to try that test is that it is quick and easy, but it is not always definitive. In other words if you piggyback all eight RAMs in a memory bank one at a time and find no change, it does not necessarily mean the parts are good (or bad). There still may be a problem lurking in one of them that was undetected. You may still wind up having to unsolder and replace all the parts to find out for sure.

    At the moment you are faced with uncertainty in the eight RAM chips in the low bank and five ROM chips. A problem in any of them might keep the machine from booting.

  5. #25
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    Excellent thx Dave.

    One last question before I get to work on the RAMs and ROMs... can we r/o it's not a component (cap, resistor etc)?
    "DAVID: Is this a game... or is it real? JOSHUA: What's the difference?" 'Wargames' 1983

  6. #26
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    Quote Originally Posted by Juleshsmith View Post
    Excellent thx Dave.

    One last question before I get to work on the RAMs and ROMs... can we r/o it's not a component (cap, resistor etc)?
    If you are asking can we assume the problem is not a passive component, then the answer is most likely yes. Re-read my message #20 and let me know your plan.

    See these links for info on RAM/ROM replacement boards:

    http://blog.tynemouthsoftware.co.uk/...nt-boards.html

    http://www.bitfixer.com/bf/petvet

  7. #27

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    Hi,i've same problem on my 8032...
    Mr Dave we wrote through private message..
    Tensions seems to be ok...mos 6545 it seems hotter than others...
    Ram 4116 are ok...but at 9 pin of cpu 6502 i read 2,5v...it's ok?

  8. #28
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    Quote Originally Posted by ilpaninaro View Post
    Tensions seems to be ok...mos 6545 it seems hotter than others...
    Ram 4116 are ok...but at 9 pin of cpu 6502 i read 2,5v...it's ok?
    Pin 9 of the CPU is the Least Significant Bit (LSB) address line and should be pulsing if the PET is executing instructions. So on a DC voltage meter, it would read the average of the voltages or about 2,5V. Test CPU pin 7, the Sync signal. It should be pulsing too and read about 2,3 V. That would mean the PET is fetching instructions properly and perhaps the problem could be a bad 6545 CRT Controller, but DO NOT unsolder it yet.

    If the Sync is struck high or low, the problem may be most likely bad low RAM or a bad ROM although there could be other less likely issues.

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