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Thread: Compaq Portable 486 Power Supply Unit

  1. #1

    Question Compaq Portable 486 Power Supply Unit

    Hi all,

    I while ago somebody donated a Compaq Portable 486. On the first try it turned on and started booting Windows 95. Yay!
    But then....

    A loud bang and some smoke! And a dead machine...

    I took it apart and found out that on the Power supply, a few capacitors had exploded along with a VDR and the fuse.
    "No big deal" is what I thought. And it woud have been.
    I desoldered all the bad components, looked them up on-line, wrote everything down and cleaned up the PCB.

    Since I was quite busy at the time, I stored everything in my collection room until I finally had some spare time to order the parts and
    go on with the repair.

    But now I've stumbled upon a problem:

    I forgot the write down where which capacitor should go
    For the major part it is not a problem because I ordered all the parts in exactly the same dimensions as original.
    But there are a few capacitors on the secundary side of the board which i'm afraid to mix up.

    My question to you guys is:

    Does anyone have a schematic diagram or some high-res pictures of this PSU-board?
    Or maybe someone can tell me which values should C23, C27, C28, C44, C63 be?


  2. #2
    Join Date
    Oct 2018
    Fontainebleau, France


    Hello FlaminV,

    I happen to have a Portable 486 right next to me.
    I disassembled the PSU and took some pictures:

    This is not so useful though since the capacitors show their values on the hard-to-see side.
    Here is what I could get:
    C23 = 470F, 25V
    C28 = 1000F, 10V
    C63 = 1000F, 10V

    I could not read C27 and C44 without removing the board, but they read "H9133" on the other side, which is the same as C28 and C63. So, I guess 1000F, 10V.

    Good luck,

  3. #3


    Hi !

    Do you know the pinout for this PSU ? Mine died and i want to do a PicoPSU but i cant find the connector pins output voltages anywhere

    Thanks !

  4. #4


    Ah , by the way :

    C23 = 470uf, 25v
    C27 = 1000uf, 10v
    C28 = 1000uf, 10v
    C44 = 1000uf , 10v
    C63 = 1000uf, 10v
    C31 = 1000uf, 10v
    C24 = 68uf, 35v

    All these caps on my PSU had leaked , so i replaced them all, ive also replaced the screen with a newer 10.4 LED ( very hard to find one that fits on original mount ) ... I was using normally , today, the PSU just dont start, as it had already failed , and the new screen uses far more current than the old CCFL backlit, retrofitting a newer more powerfull one seems to be the case.


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