Hello, I have recently attempted to fix my friend's TV. It's rather old but surprisingly the caps seem to be good, from the information I have managed to find at this site and others, I've got the PSU schematics (BN44-00158A, MODEL: SMA23-P, Rev 1.0). Symptom was PSU only delivering 5V standby voltage and nothing else, it would not power up the 12V nor the 24V rail at all. I have found that RM801 was burned and open circuit, DM804 was shorted out and RM814 had very high fluctuating resistance ranging in MOhms.
Since all those components were around ICM801S (F9222L hybrid), I considered that hybrid faulty (after replacing all the components but the hybrid, the RM801 would burn instantly after switching the PSU on). Then I have also replaced the hybrid, but it's still burning through the RM801 resistor.
Since I was unable to get the direct replacement for DM804 which was D1S4 Schottky diode, I have replaced it with 1N5819 since the parameters were close enough.
I have tested around some random components and found no faults really. I have access to an oscilloscope, DMM and a desoldering station so testing components out of circuit is easy.
Could you guys point me in the right direction? I'm stuck on the diagnosis with this one... I did search this forum throughly, but the information was insufficient.
Thanks in advance!
Since all those components were around ICM801S (F9222L hybrid), I considered that hybrid faulty (after replacing all the components but the hybrid, the RM801 would burn instantly after switching the PSU on). Then I have also replaced the hybrid, but it's still burning through the RM801 resistor.
Since I was unable to get the direct replacement for DM804 which was D1S4 Schottky diode, I have replaced it with 1N5819 since the parameters were close enough.
I have tested around some random components and found no faults really. I have access to an oscilloscope, DMM and a desoldering station so testing components out of circuit is easy.
Could you guys point me in the right direction? I'm stuck on the diagnosis with this one... I did search this forum throughly, but the information was insufficient.
Thanks in advance!
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