Buzzing noise from Imac 27 inch

Anonymous user · ‎2021-06-28

I am using a Back-UPS RS 1500 on my Imac 27 inch. It is connected all the time but when in battery mode there is a buzzing coming from my computer that unnerves me!! Any advice help appreciated I don't want to burn out my Mac!!!

BillP · ‎2021-06-28

Hi,

When the UPS goes on battery the sign wave changes to step approximated and this could be the cause of the power supply buzzing. Kbase FA158939 "Computers containing PFC (Power Factor Corrected) power supplies and their use Back-UPS and Smart-UPS SC with Step Approximated Sine waves." discusses this issue.

See Answer In Context

BillP · ‎2021-06-28

Hi,

When the UPS goes on battery the sign wave changes to step approximated and this could be the cause of the power supply buzzing. Kbase FA158939 "Computers containing PFC (Power Factor Corrected) power supplies and their use Back-UPS and Smart-UPS SC with Step Approximated Sine waves." discusses this issue.

Anonymous user · ‎2021-06-28

Hi Bill

Thanks for replying, much appreciated! I don't really begin to understand the article I was forwarded to but it does seem to suggest that the buzzing will only occur for a limited period of time. My buzzing happens for the whole time the computer is attached to the UPS on battery mode!

Am I damaging my Mac I wonder! I live in India where we have many power cuts so this is a major issue for me!

Claudia

BillP · ‎2021-06-28

Hi,

It is unlikely but the sign wave could damage the power supply of a period of time. If you experience frequent power losses I suggest replacing the Back-UPS with a Smart-UPS SUA, SMC, or SMT model. Those UPS provide a pure sign wave while on battery.