LG PSU board EAY60968801 repair

This is a short tutorial on how to troubleshoot and test the LG PSU board EAY60968801.
There is also a Youtube video with the same content.

Let's first have a look at the schematic. There are some less important components missing but it will give you an overview. (it may also contain some errors)
You can download it from here: Schematic EAY60968801

It is used in several Plasma TVs like 50PK250-UA 50PK990-ZA 50PK950-UA 50PK750-UA 50PK590-ZE 50PK550C-UD 50PK550-UD 50PK540-UE 50PK350-ZB 50PX950-UA and probably others. The schematic is very similar also to the EAY60968701. which is used in the 50PJ340-UC 50PJ350-UB Z50PJ240-UB.
_________________________________________________________________________________

Refer to these pictures to find the components mentioned in the schematic:

If you prefer the trial and error approach you can also buy the repair kits available on the internet, they probably cover most of the problems. Usually included are the standby controller IC, a nearby diode, a shunt resistor, a fuse and some of the big white power resistors.

The big white resistors are 22Ohm on the EAY60968801, not 10Ohm like the ones shown here. 

Repair and troubleshooting tips:

1. Remove the board from the TV, it will be easier to work with.

2. connect a load (two 100W lightbulbs in series or an equivalent power resistor) from VS to Ground

3. Connect AUTO_GND to GND and two switches from RL_ON and M_ON to STBY.

4. Apply AC mains voltage to the input.

5. Measure the voltage at F302, should be around 166VDC for 120VAC input. 

6. Measure STBY at P813, may vary a bit but should be around 3.5V. The microcontroller should now be working. If the 3.5V is not present you most likely have a problem with the 3BR1565 and/or D304, R305, F302.

7. Switch on RL_ON, both relays should close. I can't say if the timing is fixed but I am assuming it can vary quite a bit depending on measurements taken with the circuit around PC102. The measurement here is taken at the relay contact that is sinked (it's ON when signal is LOW)

8. check the PFC output voltage, it should be 390V and stable, check at F302 and F801, if it's not you may have a problem with the PFC circuit

9. check AC_DET at P813, should be 4 to 5V. The training manual actually says 4.1V but in our case the uC output is not loaded and therefore the signal goes up to 5V. 

10. check 5.1V at P813

11. check 17V at P813

Leave RL_ON on.

12. connect 2x 100W light bulbs to VS/GND (or an equivalent resistor with >150W)

13. Switch on M_ON 

14. VS will be turned on

15. check VS, VA and M5V and adjust them if necessary according to the voltages indicated on the panel sticker

16. When turning off M_ON the circuit around Q906 will be activated and discharge VS capacitors

Have fun.