DELL L230N-00 (aka LITEON PS-5231-2DFS-LF) PSU - no PWR_OK

[Age]

Hi All,

I have said 230W PSU failed in my girlfriend's comp recently.

On applying 240VAC:

+5VSB (Purple) measures 5V as expected.
PS_ON measures around +3.8V (is this normal ?)

Upon shorting PS_ON to GND:

+5V, +12V, PWR_OK all rise momentarily (up to about 150mV on DMM) then fall back to ~5mV

All caps appear OK on the board - can anyone give any clues where to look - or better yet have a schematic of this PSU ?

Curiously, a replacement noname brand PSU I fitted to the Dell has just failed as well after a few months of working - if it was line surge you would expect the primary side to be at fault - perhaps a flaky motherboard ?

Thanks,

Adrian

[PCBONEZ]

Re: DELL L230N-00 (aka LITEON PS-5231-2DFS-LF) PSU - no PWR_OK

Try the same thing only attach a hard drive to one of the drive connectors.
(No need for a data cable.)
Some PSU's need a load to stay on.

[Age]

Re: DELL L230N-00 (aka LITEON PS-5231-2DFS-LF) PSU - no PWR_OK

Thanks for the tip .. but the PSU doesn't work when connected to the MB - you get the dreaded Dell flashing orange light on the Power Button ..

[linuxguru]

Re: DELL L230N-00 (aka LITEON PS-5231-2DFS-LF) PSU - no PWR_OK

Not conclusive based on the symptoms, but it appears to be tripping either the overload or overvoltage protection immediately on startup. Here are some places to look:

1) One of the secondary rectifiers could have failed short. The first candidate is the one on +12v, and probably just one leg of the pair has failed, allowing the startup twitch that you noticed.

2) Some other short on one of the rails. Replace all secondary caps regardless of appearance if it is a crap brand.

3) Check the 7905 regulator (if there's one) on -5v.

4) Check the bleeder resistors for shorts.

5) Check the controller IC and supply bypass caps near it.