Back-UPS ES 750 units make hiss/buzzing noise and won't switch to outlet.

[Anonymous user]

I have two Back-UPS ES 750 units, model BE750G. A relative passed away and I was given some UPS units.

Unit 1 - Has a terrible hissing/buzzing noise emitting from the front of the unit where the power cord connects to it.

Unit 2 - Has the exact same noise as unit 1 but is less pronounced and quieter. Best way to describe it is like hearing a running faucet (not full blast) from the bathroom while you are a ways away in another room.

Both Units 1 and 2 - When I had these units hooked up to a Sony 17" CRT monitor and Dell Inspiron 8400 setup they would not switch back to drawing power from the wall outlet when they were plugged back in to the outlet. They just kept pulling from the battery and then would shut off. The PowerChute software would put the computer into hibernation, then I would plug the UPS units back into the wall, next I would bring the computer out of hibernation and read the PowerChute software. Said it was connected to the wall and charging but the batteries kept on draining and would then shut off suddenly, red battery light flashes on the unit itself. Do these units require some sort of manual reset?

[BillP]

What is the model and serial number of the unit (s)

[Anonymous user]

Now both units do not emit the hiss/buzzing noise as loud as they were at. There is still a very, very quiet high pitched noise coming from both units. I can only hear it if I get close to it, unlike before I could hear it sitting at the computer. Is this normal?

Should they be completely silent; after they are done with the normal clicking/buzzing when you initially power them on?

Unit 1

Model: BE750G

Serial: 5B1028T23919

Unit 2

Model: BE750G

Serial: 3B0827X19528

Message was edited by: risingfattoad

Message was edited by: risingfattoad

[BillP]

were these shipped or bounced around where they could have been damaged? yes, you're correct - you really should only hear the clicking or buzzing when the UPSs go to battery - during an outage or their battery self test when you power it on or command it to do so. i am not sure specifically what those noises indicate but it certainly does not sound normal.

oh and the part with not coming off of battery power when connected the wall outlet - best thing to try is just making sure its not an issue with that one wall outlet, which sounds unlikely, but i don't think it'd hurt to turn it off and leave it plugged in for a day or two to charge after you try a few different receptacles at your location just for troubleshoot's sake. sounds like you may have played with it a little and it may need some time to charge up before testing could be accurate and helpful.

[BillP · Accepted solution]

Also I Think You Should Pull The Battery Cover Off And Inspect The Battery For Cracks Or Bulging
(This Rarely Happens But It Still Can)