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Thread: Massive barn find!

  1. #11

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    my 1535 boots and has a working drive - i'd be glad to take you up on that, i'll shoot you a message.

    in other news recapped the dc-dc boards in both 1550s, and they both came back to life.. except the backlights. everything else (fdd, hdd, serial etc) works, and i can see that the screens themselves work fine (as does external vga) but no backlight. does someone far more knowledgeable/experienced have any ideas? or schematics/voltages/test points to point me towards? do the backlights themselves fail? any info would be appreciated, this isn't an area i've dealt with before.

  2. Default

    The 1550sx was available with an LCD (common) and a less common VGA Plasma option. Yes, backlights definitely can fail... I don't like to remember those days. I think the LCD backlight voltage is like 130VAC and the Plasma 33VDC. The 1520/1530 have different power supplies depending on the display type. The 1550 is a different breed and I don't recall if it had different power supplies or if there were different mainboards with voltage converters depending on the display type, or both. I have a 1550sx service manual with schematics somewhere. I'm currently getting ready to post all my Grid stuff on a website I'm building but I'll try to find this manual for you ASAP.
    My corner of the world: classicbits.net

  3. #13

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    slightly annoying news: i recapped the power board in the 1535exp, and it resurrected everything ..but the backlight! total different design, same exact symptom. or almost - this one tries to light up long enough to see that this screen at least *wants* to work.

    slightly AWESOME news: of the 17xx machines i have, the two 1755's would both *occasionally* turn on, but not if you tried driving the screen, or the hdd/fdd. the 1720 however never stayed on for even a second. totally dead. i decided to use that as a test bed for replacing those smd polymer caps with thru-hole electrolytics. hobbies are supposed to feel like torture, right?

    just replacing the 4 crustiest (and of course, least accessible) caps next to the PSU, and the machine booted right up, screen and all! i guess this means im gonna have to repair the 1755s and 1680's as well. boy this is gonna be rough.

  4. #14

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    I have 2 1550 , 1 lcd 1 plasma, the base unit can accept plasma , and there is a module for the lcd the plugs into the power supply board, i have switched my screens back and forth

  5. #15
    Join Date
    Mar 2013
    Location
    SW Quadrant of Michigan
    Posts
    286

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    AWPJudy, are you planning on keeping all the GRiD bags? I'd like to get my hands on one if you are willing to part with such.

  6. #16

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    i'm willing to part with all of them, i just have gotten around to cleaning them up and taking some photos. i've had to pause this project for a bit with some family and guests around, but i'll dive back in soon enough and get them sorted out.

  7. #17

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    Nice find! Can I ask how much you paid for the whole thing?
    I almost bought that GRiD lot, but couldn't agree on a price that worked for me because I was only interested in the 16xx models. If you ever want to sell anything related to those, please let me know, I'll make an offer! Especially interested in external drives or docks.
    Also let me know if you want help recapping the 16xx DC-DC board, I have experience doing that.
    Was a PM, but you couldn't be PMed.
    Last edited by Caleb Hansberry; August 22nd, 2020 at 11:08 AM.

  8. #18
    Join Date
    Mar 2013
    Location
    SW Quadrant of Michigan
    Posts
    286

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    Quote Originally Posted by AWPJudy View Post
    i'm willing to part with all of them, i just have gotten around to cleaning them up and taking some photos. i've had to pause this project for a bit with some family and guests around, but i'll dive back in soon enough and get them sorted out.
    Sounds good. If you could mention here when you start putting the items up for sale, and where, it would be appreciated.

  9. #19

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    How is it going?

  10. #20

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    Everything has been on hold unfortunately. Between some PCBs showing up (I designed and brought up a little homebrew minicomputer and wrote a small C standard library for it) and then starting school again, free time has been at an absolute premium. Hopefully once I've settled back into school again I can devote some more time to fixing the remaining broken machines and selling some stuff off. At least now they're in a temperature controlled environment, all the leaky batteries have been removed, and all the machines have been cleaned. I'd rather not have to completely put things off until next summer, but electrical/computer engineering school is annoyingly time-intensive!

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