Hp smps power suppy ps4321 help!!!!!!

[NConstantinou]

Dear all

i have several power supplies that when the transformer is connected on board
secondary pins are all shorted (7pins).
by removing it pins 1 and 5 are shown short and 2,3,4,6,7 are shorted between them.

i tried to find datasheet but nothing. ps is manufactured by LITEON

CAN ANYONE HELP!

THANKS.

ON PS I HAVE 4.3V ON POWER SWITCH ON

[Per Hansson]

Re: Hp smps power suppy ps4321 help!!!!!!

It is a high frequency transformer, you can't ohm measure it.
You need to use a transformer tester like a ring test, can also be done with an Oscilloscope if you Google for it.

[sam_sam_sam]

Re: Hp smps power suppy ps4321 help!!!!!!

Sometimes a ring tester does not always read the winding correctly if there not very many turns on a winding I have run into this type of issue I have seen where the two red LEDs are light or in the yellow and the transformer is still working

[NConstantinou]

Re: Hp smps power suppy ps4321 help!!!!!!

Thanks for your message.

i have noticed when transformer is installed on board and leave it rest for some time without power i get a very small resistance which means is not short but power supply has 4.3-4.5v stb voltage and is not turning on.
there is PS25A and TL594 ic on secondary side which are not short.

i checked all diodes and capacitors and non of them seem to be short.

there is a transistor near the 3 optocouplers on which i get the 2.45v
on the optocouplers on secondary side first one reads 0v and the other 2 read 10.8 to 11.5v.
i removed optocoupler primary side and i placed diode instead to see if there is getting something HOT but nothing.

do you have any ideas.

Thanks

[CapLeaker]

Re: Hp smps power suppy ps4321 help!!!!!!

Change out the caps for the 5VSB rail.

[NConstantinou]

Re: Hp smps power suppy ps4321 help!!!!!!

The 5vsb and 12v ca0s have been replaced