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Thread: Dead 386SX motherboard revival attempt

  1. #1
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    Apr 2015
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    Default Dead 386SX motherboard revival attempt

    I bought a 386SX motherboard from another user here knowing it had pretty bad battery leak damage on it. It turned out to be far more extensive than I originally thought, but after waiting several weeks for parts replacements, I got to work fixing destroyed traces and replacing all of the bad components on the board.

    Here's after cleaning the board and halfway through removing damaged components (all of the exposed copper had battery leak on it):



    Here's a couple of shots of it after I got finished with it:



    So after I finished with repairs, I stood back and powered it up and it didn't go on fire, so that's a plus. But it also still doesn't work which I was expecting, nothing this damaged usually works on the first attempt.

    While everything was off the board, I went through and tested all of the VIAs, which were good surprisingly. Since this is only a two sided board, it makes it infinitely easier to work on. When I powered the board up, I tested the power rails and ground planes and they all seemed to be working; Which makes sense because if something was shorted to ground, it usually ends up in fire or the PSU shutting off.

    Since everything seems to be working, but it still doesn't boot, it's pointing to the BIOS chip being dead. It's a 27512 EPROM, so I went in a dark room and peeled the sticker off, it looks to be pretty sad inside. Unfortunately, I don't have a way to test the EPROM because I don't have a way to dump the thing, nor do I have a logic analyzer to see if it's sending out garbage or not. I know the board is doing something because the AM386SX-40 gets warm, and so does the chipset. Both the video card and hard drive controller also have chips that get slightly warm, so there's power going around the board.

    The EPROM looks to be damaged, but I was wanting to know if anyone has any poor man hacks to dump the EPROM using like a NIC bootrom socket or something? I don't have the cash to go out and buy a ROM programmer.

  2. #2

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    If you're willing to put the 27512 in the mail with a return mailer I'd be happy to read it for you, email you the contents, and to duplicate it into a fresh 27512 (I have lots of spares).

    - Gary

  3. #3

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    Quote Originally Posted by GiGaBiTe View Post
    I bought a 386SX motherboard from another user here knowing it had pretty bad battery leak damage on it. It turned out to be far more extensive than I originally thought, but after waiting several weeks for parts replacements, I got to work fixing destroyed traces and replacing all of the bad components on the board.
    If there was that much superficial damage what do you think might have happened to the internal layers?
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  4. #4
    Join Date
    Apr 2015
    Location
    Austin, Texas
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    Quote Originally Posted by gekaufman View Post
    If you're willing to put the 27512 in the mail with a return mailer I'd be happy to read it for you, email you the contents, and to duplicate it into a fresh 27512 (I have lots of spares).

    - Gary
    I'm not familiar with return mailers, but I could paypal you the return mailing fee.

    Quote Originally Posted by Stone View Post
    If there was that much superficial damage what do you think might have happened to the internal layers?
    There are no internal layers, it's only a two sided PCB. You can use a bright light to see through the board, there's nothing inside.

  5. #5

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    Quote Originally Posted by GiGaBiTe View Post
    There are no internal layers, it's only a two sided PCB. You can use a bright light to see through the board, there's nothing inside.
    All of my 286, 386SX and 386DX boards have internal layers. I put a tactical flashlight behind them and there's nothing visible. Only some 16-bit expansion cards show traces on the other side with the light. So even they are multi-layered.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  6. #6
    Join Date
    Apr 2015
    Location
    Austin, Texas
    Posts
    688

    Default

    I have yet to find a VIA that disappears inside the board, I've been able to trace out everything front to back.

    I've dealt with multi-layer acid damaged boards before and this shows none of the signs of being anything other than a two layer board.

    That being said, if anyone has a BIOS image they think may work on this board based on the layout of the board, let me know. I can post chip part numbers and such if it helps.

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