AEC Star T3LC beeping but running fine?

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  • Behemot
    Badcaps Legend
    • Dec 2009
    • 4845
    • CZ

    #1

    AEC Star T3LC beeping but running fine?

    We got another of these AEC Star T3LC 3kVA on-lien double conversion units that it is beeping. Batteries are fine despite their age. Guy overheated one diode (told him to close the unit during 100% load), I have replaced it and burned MOSFET. Seizing fans were lubricated. Than one fan stopped working, replaced driving NPN transistor, it is OK now. All caps tested good.

    The UPS seems to be running just OK, it works from power grid, it charges, it works from batteries, it does not indicate any problem on the front panel. Yet it beeps every 60 seconds. Anybody has any knowledge about these units? What may be the problem??
    Last edited by Behemot; 05-29-2014, 12:23 PM.
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  • Behemot
    Badcaps Legend
    • Dec 2009
    • 4845
    • CZ

    #2
    Re: AEC Star T3LC beeping but running fine?

    Man you wouldn't guess this...floating ground.

    After we removed and mounted the PCB back several times, we just mounted it with 2 screws the last time. The other 8 did not have contact with grounded chasis. After fastening all of them it runs silently now. Will load it to full, this time with proper cooling.
    Last edited by Behemot; 05-30-2014, 10:56 AM.
    Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

    Exclusive caps, meters and more!
    Hardware Insights - power supply reviews and more!

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