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Thread: Repair of 5160 XT power supply

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  1. #1

    Default Repair of 5160 XT power supply

    Hello,

    I have two IBM 5160 from 1985 and 1986 with the 220V "Schrack" 130W supply.
    Both have now output at all voltage-lines. I have testes under load condition with a mainboard, cga, floppy-adapter, two fullsize-floppies.
    If I switch the supply on, at my postcard only the 12V-voltage-LED lights shortly.
    The fans are turning (220V). The fuses are OK. I measured most diodes - they seems to were OK.
    In the supplys are no damages visible.

    Have someone a hint for a typical failure?
    Means the non lighting +5V-LED, that there is the error?
    Has anybody a schematic for this supply? - In the technical reference of the XT is it not!

    thanks and greets
    Christian

  2. #2
    Join Date
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    Welcome to these forums.

    A common problem with the IBM 5160 is that a tantalum capacitor on the motherboard goes short circuit and overloads the power supply. You can see how common that is by looking at a list of 51xx motherboard failures at [here].

    A procedure for working out which capacitor is faulty is at [here]. Have you tried that?

  3. #3

    Default

    Hi, at one mainboard the C56 had a short circuit and at the other board was a faulty dram-chip.
    I changed these - and now both boards are running great with an working power supply.
    But both original power supplys are not working...

  4. #4

    Default

    +1 on Modem7's site, Follow the minimum diagnostics procedure and report back.

  5. #5

    Default

    Thanks for support, but I tested with this minimum configuration.
    Both mainboards are ok, have no short circuits and works with an other IBM supply from 1984 (made in USA).
    The faulty supplys from Schrack (mde in Europe) have both no voltage on all lines. Only the 220V-fan is turning.
    The supplys are defenitie faulty, but where can I start to search... are there typical errors?
    Last edited by vossi; August 12th, 2015 at 04:03 AM.

  6. #6

    Default

    With the PSU powered up and with nothing connected do you still get 0v on all output lines using a DMM to measure the output voltages ?, Could be Cap failure or a short, these old psu's ain't getting any younger, What tools do you have for troubleshooting. Be extremely careful when working on / inside psu's.

  7. #7

    Default

    I measured the outputs with a dmm under load with the working mainboard. I think I have to check all the caps first...

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