C128 (non D) repair log.

Discussion in 'Retro & Arcade Worklogs' started by Vanne, Jan 17, 2020.

  1. Vanne

    Vanne Member

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    So i recieved a shipment from the US a couple of days ago, and it contained (amongst other crap) a extremely yellowed USA C128 with seperate C1571 disk drive and all the manuals and crap that would have come with it from new, minus the actual boxes...

    Took it out of the box yesterday and had a bit of a muck around with it, but sadly a bunch of keys on the keyboard dont work. Boots up fine and the picture is great (better than my C128D) all the function keys arcorss the top work, as does the numeric keypad, but most of the normal keyboard keys are dead in the water. only about 10 of them work...

    I havent had the time to open it up yet, but ill get around to that over the next week or so. I cant run any of the diag software as i cant run the keys..

    Without digging a little further, generaly the 6526 seems to be where my nose will be pointing when i open it up. will probably clean and re-seat the chip and clean the connectors.. anything else you guys might know about where the issue might lie?

    the photo does the yellow zero justice, this puppy looks like its been smoking Winfields red since he was old enough to walk.

    [​IMG]
     
    Last edited: Jan 17, 2020
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  2. OP
    OP
    Vanne

    Vanne Member

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    Was tinkering tonight... Swapped out the 6525 with the known working one in my 128D. Same issue, so the issue lies somewhere in the actual keyboard.. I'll be needing to take that thing apart.. not looking forwards to that...

    Also removed a ton of dust from inside the case.. clean as a whistle now. Sadly that didn't help the keyboard any...
     
  3. flu!d

    flu!d KDE Neon 5.16

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    I should keep an eye out for a good 128, IMO they really were the holy grail of 8 bit machines and totally under rated in the day as everyone just ran them in C64 mode.

    I'd love the ability to run CP/M as well as 80 columns.
     
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  4. badmofo

    badmofo Member

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    RE the keyboard - you might have done this already but have you pulled it apart and given the membrane a once over? If it's anything like the C64 keyboard it should be a simplistic design and easy to clean / fix, maybe it's just the contacts under the plungers.
     
  5. Thalyn

    Thalyn Member

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    Give it "a good turpsing", as my brother would say. Pretty much the first step on any keyboard diagnosis for older computer systems is to pull it apart and give it a wipe down with a mild solvent of some kind - mineral turpentine ("turps") is his solvent of choice, where I'd probably opt for isopropyl myself. The membrane itself is easy enough to wipe over with a paper towel, but it can be a little tricky to do the plunger contacts.

    Have easily revived the keyboards of multiple Amigas (which sadly proved to have damage traces), Atari 65XE, ZX Spectrum 128, CPC-464, Sega SC-3000, and even a Matel Aquarius like this. And, of course, more than a few 8-bit Commodores. If there's that much dust in there, is almost certainly been worked into the contacts.
     
  6. OP
    OP
    Vanne

    Vanne Member

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    I don't think the C128 keyboard is /that/straight forwards.. its got 3 of these keys that are soldered in the switch keys no doubt. so ill need to de-solder them to pull the keyboard apart..
    *sigh*

    [​IMG]

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    Sorry bout the first picture being out of zoom, was just taking a few pics as I was going along.
     
    Last edited: Jan 19, 2020
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  7. Thalyn

    Thalyn Member

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    At least those three keys come away easy. They're just soldered onto the tangs on the back of the assembly from factory with no mechanical linkage of any kind, so a little heat and some tweezers will separate them real quick (and they're similarly easy to re-fit). Just watch for small parts as you're going, since the power LED is held in place primarily by the keyboard assembly and there's a small spring above the + key on the number pad.

    That's otherwise a very nice looking unit - especially the tin covers (unusual to see them without even a little browning). If you're feeling adventurous you might want to replace those electrolytics while you're in there, just in case, but since it seems like it's working there's nothing wrong with just leaving well enough alone.
     
  8. flu!d

    flu!d KDE Neon 5.16

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    The user port tracks show signs of being stored in a damp environment, but otherwise a very nice 128. Gawd they're a masterpiece aren't they? 8 bit bliss.

    As Thalyn stated, those keys de solder pretty easily with some fine pliers or tweezers.
     
  9. OP
    OP
    Vanne

    Vanne Member

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    ill give it a holler over the next few days, hiopefully on saterday. Lol glad i saved the little spring that came out when i was trying to look between the boards, i had no idea where that came from. :D
     

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