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Compaq T2400h UPS Repair Advice

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    Compaq T2400h UPS Repair Advice

    Hello !

    I have a Compaq branded UPS, model T2400h.

    It's making curious unhappy rattling noises when running on battery.
    Batteries are brand new and fully charged, and also tested on another identical unit.

    I grabbed a video of the noise (starts at 00:18 on the mp4 video at the Goo link below), and also took a couple o'scope shots of the waveform, both on-mains and on-battery.

    The scope connection is via a small 12VAC transformer, just to explain the scaled voltage readings in the scope photos. We are on 240V-ish mains here.

    Would anyone recognise the noise, and be able to speculate as to the source ?

    Such a nice UPS, and would love to save it!

    All the photos, video and docs here: https://drive.google.com/drive/folde...IgEtLIrMhmc_88

    I will try to attach the scope captures here too!

    Thanks for this forum to let me ask here!
    Max.
    Attached Files

    #2
    Re: Compaq T2400h UPS Repair Advice

    The video was quite a large file, so I trimmed to 5 seconds of noise and saved to a smaller (4.5MB) file.

    https://drive.google.com/file/d/1FSY...usp=share_link

    I'm thinking it might be some sort of "out of phase" situation that's causing the transformer coils to rattle. Maybe one of the NPN/PNP gate drive transistors is not at full health, and it's driving some of the power mosfets out of sync to the others.

    That's a wild guess, and so hard to work without a schematic!! Gosh, I wish Compaq shared all their old schematics and service docs, so save the world having to scrap so much hardware!

    I might try removing/testing/replacing all the transistors and see what happens.

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