Hi. Servicing a XBR75X850F with no power. Originally had no standby voltage of 3v3 -> found a defective SB260 diode (apparently a common fault) and now have this rail. No relay sound upon power up. Bypassed the POWER ON and T-Con with the standby voltage and do see the ~12v steady on the pin 26 of the power connector (T-CON). This implies bad emmc (Nick's TV repair YT videos). Replaced the BGA but still no power on LED / no relay.
Any suggestions on faults? Any schematics for this unit?
Did observe that the zener near the offline IC that feeds into opto-coupler is marked with '13B' yet the voltage is 3v3. The one marked (below this zener) @ '16B' is around 15-16v. The optos are PC123 (older units) and they appear to be ok when tested out of circuit.
No USB light flicker upon power up yet there is 5v present on the main controller board.
PS: The pics below were taken after removing the optos off the board. No blown fuses.
Any suggestions on faults? Any schematics for this unit?
Did observe that the zener near the offline IC that feeds into opto-coupler is marked with '13B' yet the voltage is 3v3. The one marked (below this zener) @ '16B' is around 15-16v. The optos are PC123 (older units) and they appear to be ok when tested out of circuit.
No USB light flicker upon power up yet there is 5v present on the main controller board.
PS: The pics below were taken after removing the optos off the board. No blown fuses.