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Thread: Restoring a 2001 chiclet

  1. #1

    Default Restoring a 2001 chiclet

    Hi. First post...
    I've just bought a project 2001.
    Fired it up, and there are several problems

    0. Wobbly fuse holder. Jammed it up for now but will replace
    1. Only 2356 bytes(or thereabouts) available
    2. Vertical lines on monitor. Constant lines, not each character
    3. It freezes after 30 seconds to a minute-no keyboard input accepted.
    4. Sticky keyboard

    It's going to be another week before i can play with it, but meanwhile, all suggestions gratefully accepted!!

  2. #2
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    First (and easiest) place to start is to very carefully lift and re-seat all the socketed chips. On such old machines, oxidation forms on the pins and sockets. This could explain items 1 (the ram chips), 2 (character rom) and 3.

    The chiclet keyboards are easy to disassemble and clean.

    Rob

  3. #3

    Default

    Ok. I've wired up a new fuse holder, and it no longer freezes

    I lifted the ram chips and reseated. No change. 2385 bytes. I'll try again next week.
    I reseated the character rom, and the screen cleared of the vertical lines.

    Now the whole screen jumps say 4 times every 10 seconds.

    Still, I'm happy with progress so far!
    Thanks to Rob for the tips.
    More later.....

  4. #4
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    Can you explain 'jumps' ? Can you hear an audible click from the monitor? If so, the video board might need attention. I had a video board on a 2001 that did this and it turned out that the years of accumulated dust on the board was enough to cause a spark to track from the flyback transformer to a mounting screw. A good clean sorted it out. It could also be dried out caps which again, are not too tricky to replace. Just be careful when working on the monitor as it can give you a nasty kick.

    WRT to the RAM, the PET kernal moves up through the address space until it finds a location that doesn't test good and sets the free memory accordingly. 2385 + 1025 bytes for zero page, stack and work area puts the failure at byte 3410. Which board do you have and which RAM chips? If it's a static RAM board, you can try swapping the respective RAMS around to identify the culprit. If you put a bad RAM in the socket for the ZP address range it will probably not boot at all. Try swapping the pair at I4/J4 with the pair at I5/J5 and report back.

    Rob

  5. #5
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    Nice that yours is counting ram! I think my character rom is bad - just displays the same character pattern. Reseating chips didn't help, though I can't help but wonder... would it be safe to pull the chips, spray them and the sockets with contact cleaner, then try again? Maybe the oxidation is enough to ensure that they won't work? It's been stored in a shed for the 6 months I've had it, but who knows how/where it was stored for the previous 25-30 years prior to my getting it.

    Note that I haven't had or taken the time to start troubleshooting mine hard-core, but the contact cleaner thing just occurred to me, and I can't help but wonder if it would be that simple....
    ---
    Currently seeking:
    * Roland MPU-401/AT (with daughter card header)
    * Magitronic K-156 Keyboard (5pin DIN w/ XT-AT switch)
    I also collect PC and C64 Sierra On-Line software!

  6. #6
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    I would VERY GENTLY clean the legs if they are oxidized. I use a pencil eraser and brace the chip legs against the corner of my desk so that they are supported during the cleaning.

    What kind of motherboard do you have?

    later,
    dabone

  7. #7
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    Contact cleaner is OK but a bit messy as some leave a residue. I sometimes use it for chip sockets which are not easy to clean.

  8. #8
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    Default

    Quote Originally Posted by dabone View Post
    What kind of motherboard do you have?
    I took a look yesterday and didn't see any defining ID's on the board so far as p/n or revision. What should I look for? Sticker on the back says Model PET 2001-8, SN 28517. My chassis has the spot for the tape player and membrane keyboard, however it's got what looks to be a 3rd-party mechanical keyboard that rests on top of the chassis (keyboard has a plastic tab on one edge that fits into the chassis cut-outs to hold the keyboard in place).

    I've also an 8032 PET with a full keyboard. Any chance that would be compatible? - my 8032 is missing the fuse assembly and the power supply has been completely disconnected from the unit. Working condition on it is unknown. I always wanted a PET, but they're rather large... I'm not sure how long I want to keep these - but I'd definitely like to get them restored before making the decision to offload them.
    ---
    Currently seeking:
    * Roland MPU-401/AT (with daughter card header)
    * Magitronic K-156 Keyboard (5pin DIN w/ XT-AT switch)
    I also collect PC and C64 Sierra On-Line software!

  9. #9
    Join Date
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    Quote Originally Posted by Maverick1978 View Post
    I took a look yesterday and didn't see any defining ID's on the board so far as p/n or revision. What should I look for?
    A six digit part number, something like 320008. The 2001's had at least 5 different motherboards depending on what types of ROM and RAM they were for. Failing that, you can infer it from the RAMS and ROMS themselves. Even easier, just take a decent quality picturer of the board and post a link.

    Quote Originally Posted by Maverick1978
    I've also an 8032 PET with a full keyboard. Any chance that would be compatible?
    From memory, they keyboards are electrically compatible but if you have the 'business' keyboard on the 8032 (with numbers instead of symbols on the top row), the mapping will be a bit wonky.

    Rob

  10. #10

    Default

    Quote Originally Posted by crock View Post
    Can you explain 'jumps' ? Can you hear an audible click from the monitor? If so, the video board might need attention. I had a video board on a 2001 that did this and it turned out that the years of accumulated dust on the board was enough to cause a spark to track from the flyback transformer to a mounting screw. A good clean sorted it out. It could also be dried out caps which again, are not too tricky to replace. Just be careful when working on the monitor as it can give you a nasty kick.

    WRT to the RAM, the PET kernal moves up through the address space until it finds a location that doesn't test good and sets the free memory accordingly. 2385 + 1025 bytes for zero page, stack and work area puts the failure at byte 3410. Which board do you have and which RAM chips? If it's a static RAM board, you can try swapping the respective RAMS around to identify the culprit. If you put a bad RAM in the socket for the ZP address range it will probably not boot at all. Try swapping the pair at I4/J4 with the pair at I5/J5 and report back.

    Rob
    I swapped i4 with j4, and i5 with j5
    Still 2385 bytes

    I think I've seen a program that tests each memory area, then reports which is failing. I'll try that some time next week. I have spare memory once I've found the broken chip, any suggestion which chip now I've performed the swap? Many thanks!


    Meanwhile, wrt the screen, the whole display "twitches", in that the whole display moves a fraction of an inch, then returns to where it was. The characters are all fine. I couldn't hear any noise.

    With an old tv, I'd normally tap it to make it stop, but I don't want to risk bashing my pet!

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