5VSB voltage oscilating - CWT PSF400S

[andrewdh]

Hi there all - a newbie to this forum

I have a CWT PSF400S-30 (photo attached) and using a basic power supply tester the voltage on the 5VSB output is oscilating all over the place between about 4.5 and 5.2.

All the other outputs are steady within scope

Also when you turn it off you hear a phhuushing/hissing type of sound for about 3 seconds

Any suggestions or toss it?



Regards
Andrew

[selldoor]

Re: 5VSB voltage oscilating - CWT PSF400S

Are there more caps under the heat sink? are they or the small ones we cant see or the small ones on the side board bulged or leaking. Can you pin down where the sound is from.
Does it fail to power up the PC.
By coincidence I think this may have been reviewed on line by one of our members and
perhaps they will comment later
http://hardwareinsights.com/wp/2011/...00s-30-review/

[999999999]

Re: 5VSB voltage oscilating - CWT PSF400S

1st guess is replace the caps in the 5VSB subcircuit, probably a couple smaller electrolytics near the front middle of the PCB. If the tester isn't placing a small load on 5VSB, do that too for the measurement.

[andrewdh]

Re: 5VSB voltage oscilating - CWT PSF400S

Thanks for the reply

I have taken some more pics and grabbed one from the link you posted.
Note the two caps with red circles under the heat sink in pic .....002.jpg are slightly rounded on top.

Also the two pics (005 and 006) are of the back side line up using the red circle with 005.jpg being under the heatsinks.

I plugged it into an Intel D915GAV mobi and the attached pic shows the power ready from the BIOS. However the second I turned on the PSU power switch on the back of the PSU (mains already live) the CPU fan started and the device cables were all live BUT the POST did not start until I pushed the front switch.

At that stage it booted fine however you can hear a sound similar to a "slightly" noisy fan bearing coming from the PSU. It is still there even if the PSU fan is removed momentarily.

Exited POST and shutdown with font switch - CPU fan keeps going

A real weird issue this one but maybe one of you experts can pinpoint the issue. Normally I would toss it but I am keen to learn more about what ticks or does not tick in these

The article you referred to states they are a decent quality PSU with dual 12 volt rails

Regards
Andrew

[999999999]

Re: 5VSB voltage oscilating - CWT PSF400S

Yes definitely replace the two bulged caps and retest.

[andrewdh]

Re: 5VSB voltage oscilating - CWT PSF400S

Yes definitely replace the two bulged caps and retest.

Sounds like a job for the weekend seeing tomorrow last day before easter.

Thanks people - will keep you informed.

BTW - anyone know much about PCB boards for Automatic Coffee Machines - have about 6 to fix (maybe better in a different thread) - mosfet's galore!!!

[ben7]

Re: 5VSB voltage oscilating - CWT PSF400S

Yeah, replace all the fuhjyyu capacitors too, they are a crappy brand.
Hissing usually is from a loose transformer core or from voltage ripple that doesn't get filtered out by [bad] capacitors.

BTW - anyone know much about PCB boards for Automatic Coffee Machines - have about 6 to fix (maybe better in a different thread) - mosfet's galore!!!

That would be interesting, although I don't know anything about them.

-Ben

[rogfanther]

Re: 5VSB voltage oscilating - CWT PSF400S

From c_hedge article, this psu is full of Fujhyus. They are replace on sight. Replace all of them then retest.

[c_hegge]

Re: 5VSB voltage oscilating - CWT PSF400S

Yup. I had exactly the same problem with the one I reviewed on Hardware Insights. The 5vsb caps went bad and it mad a horrible squeal when plugged in. The other caps were probably not far off failing, judging by the high ripple. I still have the PSU, but it has been recapped with panny FC and FK.