ATX PSU failure and diagnostics
 

Good day all!

I have an ATX power supply for a small form factor PC (Shuttle, I-will
XPC) and it is currently broken. Inspecting the power supply, i found
out that when I jumper Pin 14 and Pin 15, the fan will spin (indicating
that there is power) however it will die out eventually after a few
seconds. After working with GOOGLE and searching forums and all, I
found out that a certain TTL transistor is responsible for latching the
circuit from POWER_OFF to POWER_ON, the problem is, Im not pretty sure
if this is the right diagnosis, and if there are other possibilities
why this PSU wouldnt power up.

I would really appreciate if anybody can give an insight to this, I
would give further details on my troubleshooting if asked. :)

thank you very much

- Mannix

Hi
Den Mon, 26 Sep 2005 20:30:51 -0700. skrev :

snip
found out that a certain TTL transistor is responsible for latching the
circuit from POWER_OFF to POWER_ON, the problem is, Im not pretty sure
if this is the right diagnosis, and if there are other possibilities
why this PSU wouldnt power up.

That's proberly not the problem, there will be a 100 other reasons. Is
folds back for safety reasons, indicating that there is a problem with the
output voltages.

My best bet is capacitors, capacitors and capacitor. Replace all
electrolytics, except the primary ones (2 fat ones rated 350v or so) and
you're back in business. Remember to use 105deg low esr types.

I would really appreciate if anybody can give an insight to this, I
would give further details on my troubleshooting if asked. :)

http://repairfaq.ece.drexel.edu/sam/smpsfaq.htm

An excellent introduction. Read it and understand it.

Best whishes
--
Med venlig hilsen

Christian Treldal