• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Fixing PSU whine

Status
Not open for further replies.

chico

New Member
My computers PSU makes a high pitch whine. Its quite annoying. I opened it up and listened for the noise but couldnt really tell where it was coming from. (It may have been lowest on the AC input filter... maybe i think my mind was playing tricks on me).

Does anyone have any ideas of how to fix this? I have googled this extensivly and just seen a lot of contradicting stuff. Some say its the inductors and some the caps. I tried pushing a rubber eraser against the inductor coils but that didnt help.

It is a switching PSU not linear as a note.
 

fastline

Member
FWIW, I think every time I have had something whining, it was either a shorted component causing excessive current or a cap that has failed, causing an unstable circuit.
 

chico

New Member
would i test to see if a cap has failed by simply measuring its capacitance out of the circuit or do i have to have certain resistances?
 

fastline

Member
Cannot test in circuit without an ESR meter. Out of circuit cap testing might be your only option. I am sold on ESR testing though.
 

debe

Active Member
ESR meter only way to check caps quickly & easily in SWMPS. In circuit & discharged first. Ordinary cap testers & ohm meters are no good. Only other way is replace all caps.
 

Attachments

Last edited:

chico

New Member
but if i take it out i can just measure the capacitance right?
There are only a few caps on the PSU... or a few big ones.
 

fastline

Member
The debate comes up often that capacitance testing does not accurately measure the effectiveness of the capacitor. The ESR meter measures the internal resistances at a given frequency. I specifically just repaired a SMPS circuit that was whining and would start and stop the load constantly. It turned out to be 2 small value caps that tested GOOD out of circuit with a cap meter but tested WAY out of spec with the ESR meter.
 

killivolt

Well-Known Member
The debate comes up often that capacitance testing does not accurately measure the effectiveness of the capacitor. The ESR meter measures the internal resistances at a given frequency. I specifically just repaired a SMPS circuit that was whining and would start and stop the load constantly. It turned out to be 2 small value caps that tested GOOD out of circuit with a cap meter but tested WAY out of spec with the ESR meter.
So, are you saying that the test should be taken out of circuit or in circuit?

Would either be the same?
 

debe

Active Member
The picture i posted is a SMPS & capacitor testing in circuit & its faulty. Using this method is quick & easy.
 

SABorn

New Member
The simple thing is if you are going to remove them for testing, than you may as well put new ones back in as the cost is bugger all, and saves the hassle of testing, very rare the large caps will be the problem normally always the little ones that cost nothing much.

Pete.
 

Sceadwian

Banned
You could guess all year and replace half the components in the PSU and never find it. Get yourself a microphone and using spectrum analyzer software like
DL4YHF's Audio Spectrum Analyser
watch the spectral intensity as you move the microphone around the PSU, you should be able to locate the exact source within a few minutes.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top