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Thread: Replacing a tantalum capacitor on a Tandon tm-100-2A drive

  1. #1

    Default Replacing a tantalum capacitor on a Tandon tm-100-2A drive

    Hi,

    I've got an IBM 5160 with a Tandon TM-100-2A diskdrive that is shorting the 12V rail.
    When I unplug the diskdrive the PC boots fine. With the drive plugged in the PSU fan spins but nothing else happens.

    Thinking this is most likely a capacitor issue I found a capacitor on the PCB that went short-circuit (C36 on the PCB, marked 4.7 16 on the capacitor). I'm assuming this is a 4.7 microfarad tantalum capacitor with a 16V rating.

    To make sure I desoldered the cap and did a measurement with my multimeter. And for sure, it is shorted.

    I don't have any spare 4.7 / 16v tantalums here, but I do have an electrolytic one. Is it possible to replace this tantalum with a 4.7 microfarad 50V electrolytic capacitor ?

    Thx

  2. #2
    Join Date
    Jun 2012
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    UK - Worcester
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    2,686

    Default

    You can if you really want to (as long as it is something like a power rail smoothing capacitor).

    You can certainly do it as a 'test' to make sure that was all that was wrong of course.

    These types of capacitor are 'ten-a-penny' so I would buy a replacement tantalum for the long term repair.

    Dave

  3. #3

    Default

    Tantalum capacitors have lower ESR and better high frequency response than regular electrolytics. Running an electrolytic significantly below its rated voltage can cause spotty erosion of the dielectric. This can lead to earlier failure.
    Still, the capacitor will likely last longer than the tantalum cap you took out. I wouldn't worry about it. As for value, anything from 0 to 15uf would most likely work fine. When I find such capacitors shorted, I often just clip them off and go on with trouble shooting. There is usually more than enough bulk capacitance from the other capacitors on the line. I put a note on it for future replacement. The capacitor right at the regulator output is an important one and shouldn't be run without it but those at the ends of the wire at the loads are less critical. Most of the 12V line capacitance is to compensate some for the motor startup and noise isolation.
    Dwight

  4. #4

    Default

    Thanks a lot for the replies ... I went ahead and replaced it with an electrolytic and the drive is working fine now !
    I will order a new tantalum for the long term repair.

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