No boot and random shutdown

[starfury1]

Re: No boot and random shutdown

I dont know with those psu's how or what you might be looking for but the PG sig does have a limit range and there is a circuit for it at lest in the older TL494 types
I thing max is 500mS (ATX spec) but most are around 350mS
it used to be build around a quad op amp.

The above is if memory serves me correctly

Since your voltages are a bit low I am incline to think this may be some kind of indicator that as pcbonez has said something drifted out of tolerance.

I have known of smaller value caps to fail
and one supply I had years ago would not start while plugged into mains...I had to unplug it...in that case it was a dry joint on a resistor
I have no idea what the resistor was for and can only summarize it had something to do with some sort of discharge or reset or flip flop action in the psu.
once soldered it was fine...

so guess you looking for something more subtle as the fault and possibly heat related

lower value caps around controller or were ever the PG line goes might possibly be a good stating point.
but not necessarily the real fault, semi's as you say have been known to go leaky resistors high in value etc and joints faulty

so this one may lead you a merry chase.

since there is 2 posted with very similar fault descriptions it possibly does have a common cause.

anyway just my thoughts and I could be wrong

cheers

[starfury1]

Re: No boot and random shutdown

Sound like you got some idea what your doing with electronics so
if you really want to rap your head around something maybe this will give you food for thought.

older stuff so you probably going to have to work it out to what you got

http://www.repairfaq.org/sam/smpsfaq.htm

http://www.pavouk.org/hw/en_atxps.html



no answer but might twig you to something

HTH

cheers