HP DPS240MB no power

[kevin!]

Hi, I recently found in street a tower HP COMPAQ DC7900 SFF, its problem is that it does not turn on, I put another PSU and this turned on, I checked the capacitors they look good. I make the green cable bridge to ground and it does not start.
Is there any known problem about this PSU?
The PSU is a HP DPS240MB.
2 months ago repair a very similar, had an inflated LTEC capacitor, I replaced it perfect, and it worked again.
When I can, I will dismantle the PCB and take photos, I do not have much time .
Bye

[PeteS in CA]

Re: HP DPS240MB no power

The manufacturer is actually Delta Electronics (= Delta Products). The model number alone told me that (because I used to work for Delta), but it's on the label as well. It looks like the main transformer has a date code of "0830", which means the 30th week (last week of July or first week of August) of 2008. Based on that age and assuming the output connector is a standard 20- or 24-pin ATX pin-out and color-code, check the purple wire pin to see if it has +5VSB. If it does then the problem is in the main loop. If it does not then the problem is in the Standby regulator circuit. If the latter, the common problem is the small electrolytic caps in that circuit.

Being 9 years old, any output caps that are not of the known good brands (Chemi-Con, Nichicon, Panasonic, and Rubycon) should be considered suspect. Especially if you had to blow out a lot of dust to get that internal picture.

[kevin!]

Re: HP DPS240MB no power

Okay, thank you very much, when I can, I'll check to see if the PSU is a sign of life.
I'll try changing the capacitors.
There is no 5VBS, check the other capacitors. The input part is fine, the large capacitor had 250v accumulated.