13 Dec
2006
13 Dec
'06
2:38 p.m.
It is on the CPU side. It sounds like there is a high voltage leakage
problem. Before I open it for an investigation, could somebody with
experience give me directions about what is the usual cause of this problem,
which component to check, and how to fix the problem? I have experience with
analog circuits. Thank you!
A squeaking SMPSU normally means it's detecting an error (overcurrent,
which may, in turn be due to overvoltage tripping a crowbar circuit which
then shorts out the suppyl), shutting down (the oscillation frequency may
then go trhough the audible rangs), then starting up and trying again, etc.
If the problem is certainly inside the supply (i.e. it contines doing it
on summy load), I'd suspect either a failure of the regulation feedback
loop (thus casuing the overvoltage problem), or a shorted capacitor or
rectifier diode on the scondary side of the supply.
-tony