Electronic – seeking help identifying small buzzing transformer from the UPS, or advice on how to silence it

transformerups

i have an APC brand UPS installed inside another project, and have just recently powered it up for long durations for the first time. and i've picked up an annoying buzz in a small transformer on the main circuit board :<

i'm certain this little jerk is the only thing buzzing, but i've failed to find it online for R&R.

buzzing transformer

the text reads :
430-0271-Z.
VIKING F-1.
LEI-4 BJ08.

the buzzing is present intermittantly when the mains power is connected, and transitions to a steady sound when battery is unplugged. it goes away completely when battery is plugged in and mains is disconnected, so i conclude it's part of the charging circuit.

could a faulty battery cause this problem?

if it's a custom part for APC, and i can't source a replacement, is it safe to muffle the buzzing with some self-adhesive duct foam? i mean the black mat material used to insulate commercial air conditioning ductwork. it's a dense heat-resistant rubber foam.

Best Answer

You have given no indication that the transformer is broken, and that replacing it will therefore do anything useful.

Options are:

  1. Live with it.

  2. Get a different UPS.

  3. Muffle the whole UPS somehow, keeping in mind its need for ventilation.

Adding foam to the board, or doing anything else inside the unit is a bad idea. You don't know what each part does, and what thermal considerations it has. You shouldn't be inside something with dangerous voltages without really understanding it anyway.

Perhaps you can put the whole UPS inside a cardboard box with sufficient vent holes to allow air flow. The holes can be arranged to muffle sound in the direction you care about. If you do this, at least at first, put a thermometer in there and monitor the ambient temperature the UPS will now see. Check the UPS datasheet and make sure you're not exceeding its requirements. You need to check this under sustained maximum load, both while operating from the line and from the battery.

I'd probably just get a different UPS and use the first one in a different place where noise is less of a issue, or sell it, or something.

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