UPSes making buzzing noise on various PCs...

[Anonymous user]

This is something that bothers me, but whenever either of my UPSes kick into their self-test mode in which they slightly discharge the connected PC makes an annoying buzzing noise from its PSU. This also does the same on a SCPH-90001 PS2. Why is that and should I be concerned?

[Erasmus_apc]

What UPS model are you working with, and do you have any specs on those power supplies?

[BillP]

[this thread|http://forums.apc.com/spaces/5/smart-ups-symmetra-lx-rm/forums/general/4711/symmetra-communications-...] may have some helpful info and is probably similar to what you are seeing. we can confirm once you provide the info Erasmus asked for.

[Anonymous user]

Sony doesn't release schematics on the PlayStation 2, but the SCPH-9000x has an internal PSU that is at 32W. My desktop PC has a PC Power and Cooling Quad Silencer at 750 Watts. The PS2 is on an ES 350 while the computer is on an XS 1300.

My only other concern, and that I do realize multimeters are not reliable in testing AC voltages in stepped sine mode, is that why I only get an 80V readout as opposed to the XS 1300's 115?

[BillP]

if you are using a true RMS voltmeter, you should be reading 115v from a step approximated sine wave. if you use a non true RMS voltmeter, you will receive 80-88v.

[see this article for reference|http://nam-en.apc.com/cgi-bin/nam_en.cfg/php/enduser/std_adp.php?p_faqid=1493]

[Anonymous user]

It's only a $7 meter so I don't think it's going to have RMS. I only got it for mainly DC metering (mainly alkaline batteries).

[BillP · Accepted solution]

yeah i agree, most likely it is not true RMS. usually it says it right on the actual voltmeter if it is.