Hey all so I have this other set that I have been working on for a while. Originally I received it with flickering pic upon startup. This is attributed to failing surface mounted caps 25v 33mfd going south on the y sustain. Well my father in law ran this set for 2 years after I repaired it. But started it again so I used the heat gun method on the y board and pic came back.
While its having the issue the transformers in the vs circuit are making a heck of a noise. When I find the offending cap on the y board the hiss in the power supply goes away. But this time as I powered up it blew a ceramic resistor 2.4 ohm off the vs load on the power supply. I believe it's for power sensing through a series of components and makes its way to an optocoupler. I replace the burned out rectangle ceramic power resistor and still no vs. va comes up for a split second until power supply shutdown causing a 5 blink alarm on the power supply error led. So I get va momentArly no vs. all low voltage dc supply's are there. The odd thing is that the power supply has a va and a vs ok signal from mainboard seperatly . Both are 3.3v at the time which leads me to believe the issue is mainly in the power supply. Pfc is working. I have dc to the primary's of the vs transformers but no secondary output from what I can tell with my fluke. I have tested signals from the vs on optos and the two are inline with va on on the va side. Just no vs output. I'm stumped. I have tested all switchers diodes and fets. Anyone else run into this? This is a lg built set and the unit is basically a sampo. 2003 build date. Power supply is manufactured by powerex pw-1550 and the resistor that originally blew is r24 and lg part number on the board is 3501q00004a
Oh and I have tried disconnecting y and z from power supply too and there are no shorts between vs and ground so nothing loading down the supply.
While its having the issue the transformers in the vs circuit are making a heck of a noise. When I find the offending cap on the y board the hiss in the power supply goes away. But this time as I powered up it blew a ceramic resistor 2.4 ohm off the vs load on the power supply. I believe it's for power sensing through a series of components and makes its way to an optocoupler. I replace the burned out rectangle ceramic power resistor and still no vs. va comes up for a split second until power supply shutdown causing a 5 blink alarm on the power supply error led. So I get va momentArly no vs. all low voltage dc supply's are there. The odd thing is that the power supply has a va and a vs ok signal from mainboard seperatly . Both are 3.3v at the time which leads me to believe the issue is mainly in the power supply. Pfc is working. I have dc to the primary's of the vs transformers but no secondary output from what I can tell with my fluke. I have tested signals from the vs on optos and the two are inline with va on on the va side. Just no vs output. I'm stumped. I have tested all switchers diodes and fets. Anyone else run into this? This is a lg built set and the unit is basically a sampo. 2003 build date. Power supply is manufactured by powerex pw-1550 and the resistor that originally blew is r24 and lg part number on the board is 3501q00004a
Oh and I have tried disconnecting y and z from power supply too and there are no shorts between vs and ground so nothing loading down the supply.
