monitor

I recently purchused two HP 1755 LCD monitors from Ebay.(both are in great shape) wiht the exception of one, during sleep mode lets off a quiet yet high pitched squeck.(lol spell for sh*t) If I shut off power from the front power switch it still squecks, but if I shut it off from the back power switch the squeck stops. Is it dust or some other minor issue or something more serious?

 

sounds like a capacitor problem, never had a monitor do it but i had a tv that would. i had to unplug it and wait for the capacitor to discharge, hence the squealing sound.maybe someone else with more knowledge can help you better.

 

The front power switch appears to only put it in standby so there is still current flowing through the power circuits, and as suggested a faulty capacitor. Send it back. If you can't, then you just learned a lesson about the risks of buying off ebay. A reputable technician should be able to fix it.

 

Hi,

Switching power supplies run an oscillator at about the frequency you describe. Usual cause of hearing the oscillator is an inductor, which it has, with loose windings or cores. That one was bad when you got it. Hope this helps a little.

Luck, Jim

 

Windings and cores are found on transformers and the typical sound they make when loose is a buzzing noise. This was described as a high pitch squeak which leads me to believe capacitor.

 

Windings and cores (normally called chokes unless referring to transformers) will resonate at any frequency, not just lower ones. This is a common problem in cheap power supplies emitting a high pitched squeal even though there running on base 60hz. For example: In a camera flash circuit it is not the capacitor that makes the well known high pitched upwards tone slope but the charging transformer. Also capacitors are incapable of making any sound whatsoever, to my knowledge.

If your comfortable taking apart the monitor, a touch of hot glue on the chokes will most likely solve the problem. Attached is a common power/inverter board for a LCD monitor with the chokes circled.

 

Hi Dig,

Windings and cores are found on ALL inductors/transformers etc. I've been repairing Audio, Digital and Computers for going on 60 years. I have heard many a squeal from inductors.

Jim