APC UPS - High pitched annoying sounds

[MWP]

Greetings all

I have an older APC 2200 SmartUPS.

It works perfectly, but constantly emits a very high pitched squeal that varies in amplitude slightly every few seconds.
It is *very* annoying. Bordering on headache inducing.

Other than moving the UPS into another room, or boxing it up somehow, does any have a suggestion on how it can be silenced?
I am an electronics tech, so am not afraid to work on it internally ... but i'm not sure where to start looking for the noise source, or how to solve it.

Thanks in advance.

[Delta]

Check that the magnetics and caps are physically secure. A blob of hot snot might not go amiss!

[BradC]

The APC SmartUPS series have a number of evolutions. Older is a relative term. Roughly what year is the unit and has it been doing it long?

A complete left field one to think about, but I had a unit that had lost its cal and was overcharging the batteries. The batteries were squeaking as each cell periodically vented past the rubber cap. A most odd noise to be sure.

I can't offer any more advice until I get an approximate age, as the charging & inverter circuits varied quite significantly from generation to generation. Mine are annoying enough that I put one in the granny flat and one in the garage. I could not stand to have it in my office because of the transformer hum. One is a 98 and the other is a 2001. Both different generations but similar charging methodologies.

My general method for locating noises like that is a bit of 1/4" vacuum hose in one ear, and sweep it around the board looking for the noise source.

[MWP]

It has a manufacture date of 06/02/05.
It looks identical to this:


It has made the noise ever since i've had the UPS which is about 6 years. It has had new batts installed during that time too.
Im guessing the freq of the sound is around 10khz or so.
The noise hasn't bugged me in the past as its normally been in a noisier environment (i've just moved house).

Thanks guys, ill pop the top off again later and have more of a poke around.

If youre interested, here is a serial data dump from it:

Code: [Select]

DATE     : 2015-11-16 14:05:58 +1030
CABLE    : Custom Cable Smart
DRIVER   : APC Smart UPS (any)
UPSMODE  : Stand Alone
STARTTIME: 2015-11-15 10:40:37 +1030
MODEL    : Smart-UPS 2200
STATUS   : ONLINE
LINEV    : 246.2 Volts
LOADPCT  : 17.5 Percent
BCHARGE  : 100.0 Percent
TIMELEFT : 86.0 Minutes
MBATTCHG : 5 Percent
MINTIMEL : 3 Minutes
MAXTIME  : 0 Seconds
MAXLINEV : 246.2 Volts
MINLINEV : 244.8 Volts
OUTPUTV  : 246.2 Volts
SENSE    : High
DWAKE    : 0 Seconds
DSHUTD   : 90 Seconds
DLOWBATT : 5 Minutes
LOTRANS  : 208.0 Volts
HITRANS  : 253.0 Volts
RETPCT   : 15.0 Percent
ITEMP    : 33.3 C
ALARMDEL : 5 Seconds
BATTV    : 54.8 Volts
LINEFREQ : 50.0 Hz
LASTXFER : Automatic or explicit self test
NUMXFERS : 0
TONBATT  : 0 Seconds
CUMONBATT: 0 Seconds
XOFFBATT : N/A
SELFTEST : NO
STESTI   : 168
STATFLAG : 0x05000008
REG1     : 0x00
REG2     : 0x00
REG3     : 0x00
MANDATE  : 06/02/05
SERIALNO : JS0523036976
BATTDATE : 18/11/11
NOMOUTV  : 220 Volts
NOMBATTV : 48.0 Volts
EXTBATTS : 0
FIRMWARE : 654.12.I
END APC  : 2015-11-16 14:06:21 +1030


[BradC]

Right, so its the same generation as my 01 model. It's the first generation of APC units that used almost entirely SMD construction. Maybe start looking around at the MLCC caps around the charger asic.

I don't have a circuit for that model, but it's not terribly different to the older model which *does* have a circuit floating around the net. Part numbers don't correspond of course.

The charge circuit is an interesting animal. It uses the main transformer as an inductor in a boost converter to charge the batteries and it does this using high frequency pwm. It may not be the problem, but it's a place to start. Interesting waveforms on the transformer primary if you start poking around with a CRO. You kinda think "what the hell?!?".