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  1. ajgriff

    Commodore Pet 3032 no power

    Here's a crop from an image attached to post #9. Worth experimenting with the routing of the PSU and monitor interconnect cables I would have thought. Alan
  2. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    It's possible of course that probing is just remaking a dodgy contact/connection. Alan
  3. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    Manual attached. Alan
  4. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    Worth seeing what happens with the emulator installed I would have thought. Alan
  5. ajgriff

    Commodore Pet 3032 no power

    I know from personal experience that the Western Design Centre W65C21 and the Motorola MC6821 are suitable replacements for 6520 PET PIAs although I'm sure there are other equivalents. Alan
  6. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    I've just read the first page of this thread again. A couple of observations: 1. The PET didn't display an image at all using the original character ROM. 2. Things seemed to go seriously awry when the 2114s were first used in the video RAM positions. Alan
  7. ajgriff

    Commodore pet flickering screen

    My guess is that you have an intermittent connection between the transformer and the VDU. The voltage rise will reflect a change from load to no load due to the intermittency. Clean the connection to the VDU board and see what happens. The random character screen is a different issue but at...
  8. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    That's an acceptable Hi signal as far as I'm concerned and it doesn't look like there's a problem with the reset circuitry. Overall I'm a bit confused and wouldn't be testing the RAM chips with the Tynemouth board in test mode. Also I think it's worth sticking to using just one CPU. Alan
  9. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    No, the characters' positions will not be identical to the example image and they will change on restart. If you're sure you've identified all the faulty 6550s and that both CPU's are ok try removing the PIAs if you've not already done so. Alan
  10. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    Have you got 2 CPUs? Alan
  11. ajgriff

    Commodore PET 2001-8 stuck on garbled screen

    I assume this means you've replaced the character ROM and that you still get the garbled screen when using the Tynemouth board's ROM & RAM. Presumably this is the early static RAM logic board with socketed RAM chips. If so it looks like there's a problem with at least one of the video RAM chips...
  12. ajgriff

    Starting my first Pet, a 4032 in desperate need of some love

    Bitfixer's ROMulator includes a NOP generator and Dave's PETTester V4. You may struggle to find a schematic specific to the 8032089 PCB. However you should find that the 8032090 schematic is close enough. Any differences are likely to be very minor. Alan
  13. ajgriff

    Neglected PET needing some love

    You could try something a little more abrasive like very fine (1600+ grit) carbide paper. Nothing much to lose at this stage. Alan
  14. ajgriff

    Neglected PET needing some love

    Before going any further please try abrading a few rubber keypads with plain printer paper before testing with the keyboard assembled. This is a tried and tested method of reviving keyboards of this type. I think you'll be surprised at the results. Alan
  15. ajgriff

    Neglected PET needing some love

    It's the rubberised plunger pads that need cleaning. Colin's 'paper method' seems to work well. Alan
  16. ajgriff

    PET 2001-8 Repair Assistance Needed

    That seems to be the perceived wisdom Hugo but I'm only going by comments gleaned from the web such as this article: https://www.atariarchives.org/creativeatari/New_RAMS_for_Old.php Seems plausible. Alan
  17. ajgriff

    PET 2001-8 Repair Assistance Needed

    It looks like this PET is displaying available RAM in line with that of an 8k machine in which case the system chips are likely to be 4108 dynamic RAMs (half faulty 4116s). Also the holes are consistent with Commodore's policy of making it difficult to circumvent their pricing structure by...
  18. ajgriff

    PET 2001-8 Repair Assistance Needed

    Isn't this a dynamic PET with soldered RAM chips? If so swapping chips around isn't that easy unfortunately. Alan
  19. ajgriff

    PET 2001 Booting Issues

    Yes and there's little point in spending a large amount of money on a laboratory grade oscilloscope which will only see occasional use. Alan
  20. ajgriff

    PET 2001 Booting Issues

    The Hantek does seem to get reasonable reviews. People say that there's a fairly steep learning curve when learning to drive them. As a long time analogue scope user I'm not best placed to advise but I can see the attraction of a piece of kit that could be put to use in other settings. Alan
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