LCD PS repair (17PW06-2)

[rodrigopires]

I have a lcd tv with no power on, no standby light, no sound, no image, nothing... looked in the PSU and found a blown IC (IC303 - ICE3BR0665J) and a shorted diode (D321 - SB5B0) replaced those two and still not fixed. I got 210v on pin 5 IC303 and 2.5v on the 12v aux from TR300. Same with the other transformer TR200 with 213V on pin 1 and 2.7v on pin 2 (24v aux). Primary side is OK at 400V.  What could be the source of the problem?

[fzabkar]

What voltages do you measure at PL200 and PL201?

BTW, I would replace all 4 parallel connected UF5402 diodes as a set. If any diode has a slightly lower forward voltage drop, it could end up carrying all the current.

[coromonadalix]

yeah   a cheap way to boost the current capacity     

[mikerj]

I got 210v on pin 5 IC303 and 2.5v on the 12v aux from TR300. Same with the other transformer TR200 with 213V on pin 1 and 2.7v on pin 2 (24v aux). Primary side is OK at 400V.

Are these static DC levels or is the output of IC303 actually switching and you are getting the average voltage via a DMM?  Having a constant DC drop of ~190v across the primary of that flyback transformer suggests it's open circuit.  It will have a fairly low DC resistance so there would be smoke and flames if there was continuity.

[rodrigopires]

I dont have an osciloscope to check the waveform my only tool is a DDM, in dc mode i get a more or less contant 210V and in AC mode it jumps from 0 to around 307V and back to 0 on and on about one time a second, using frequency mode i wasn't able to get a reading... Also the 2.5v i get on the 12v AUX were mesured in AC mode, using DC mode it does not show a reading. I dont know what more to check...

Also replaced the remaining 3 diodes but with no change.