42" LG Plasma won't turn on

[neutron561]

I thought I could fix this TV for an elderly friend because I have a sorder sucker and changed caps in my own set before. Maybe not! She says the set was fine last time she turned it on, then the next day would not turn on.

Product Code: 42PA4500-UM.AUSLLHR a LG 42” Plasma TV
S/N: 208RMSSAL382
Mfg.: August 2012

Symptoms:
Set dead, Won't turn on and NO click.
Standby LED is on red
No response when power button is pressed (I don't have the remote)

With back taken off:
5.25 volts DC on Standby terminal on Power Board. Upwards of 200 volts DC at other points such as SUS boards. Other lower DC voltages at logic board. I may be wrong but not leaning toward the power board.

No swollen caps identified.
There is a solid Red LED on the Main Logic Board (p/n 42PA4500-UM(1.1))

A Green LED on the Control Board is flashing the sequence -.-.- pause & repeat.

Is the Green LED a trouble code that will identify which board in trouble?

Power goes from power board to the ZSUS board, then another wire harness from the ZSUS board to the YSUS board.

Does anyone have knowledge of Blink Codes that will help me identify which board I need? What does this code tell you?

Where is a starting point to troubleshoot and save this TV from the landfill? I don't want to start replacing boards without a good idea as to what the issue is.

Thanks for any help

[dick_barton]

Re: 42" LG Plasma won't turn on

What are the voltages on P6 & P7?

[neutron561]

Re: 42" LG Plasma won't turn on

If I am at the right pins, 5.25 vdc on each. Is that the plug on the power board going to the Main Logic board?

[neutron561]

Re: 42" LG Plasma won't turn on

I think I was on the wrong place. P6 = 55.2 P7 = 5.24

[dick_barton]

Re: 42" LG Plasma won't turn on

P6 has 15 pins with the expected voltages written on the pcb board just above the connector and also what voltages are on the other connector with 7 pins

[dskall]

Re: 42" LG Plasma won't turn on

I am no expert, so for what it's worth. I believe the green light is what they call a heartbeat light. It should blink once a second if healthy and once every 3 seconds if there is a problem. I have played with a few plasmas and every one had a problem on the left side. ysus and or buffer board. Look at your buffer chips far left green board. See if any show damage. Besides this great forum youtube is also good source. You might want to look up how to check buffer boards for shorts. Hope this helps some.

[neutron561]

Re: 42" LG Plasma won't turn on

Got it. First, Thank you very much for the help.
Tomorrow I will have to fashion something to connect my meter lead to P6 in the 15 pin area without shorting something.
For P7: pin 1 & 2 = 205 vdc, pin 3 & 4 ground, pin 5 = 55.2 vdc, pin 6 = 5.24 vdc

[neutron561]

Re: 42" LG Plasma won't turn on

I am no expert, so for what it's worth. I believe the green light is what they call a heartbeat light. It should blink once a second if healthy and once every 3 seconds if there is a problem. I have played with a few plasmas and every one had a problem on the left side. ysus and or buffer board. Look at your buffer chips far left green board. See if any show damage. Besides this great forum youtube is also good source. You might want to look up how to check buffer boards for shorts. Hope this helps some.

Thanks dskall. That makes sense.

[ReeceyBurger123]

Re: 42" LG Plasma won't turn on

Hang on where is the heatsink for the Xbuffer gone on the bottom of the panel ?

[dskall]

Re: 42" LG Plasma won't turn on

With no click when you hit power button you might want to check for voltage change at your button connector when you press power button.

[dick_barton]

Re: 42" LG Plasma won't turn on

Hang on where is the heatsink for the Xbuffer gone on the bottom of the panel ?

+1
I believe from what I have read that you will damage the Xbuffer boards if you run the set without the heaksink in place

At the top of the panel there's a sticker giving voltages. Can you post an image of the sticker.

[neutron561]

Re: 42" LG Plasma won't turn on

OK Dick, here's todays readings for P6: (all volts DC)
1. 55.2 vdc
2. 55.2 vdc
3. 55.2 vdc
4. .016
5. .016
6. 17.96
7. 17.97
8. 0 GND
9. 0 GND
10. 3.29
11. 1.59
12. 1.49
13. .043
14. .021
15. 5.23 vdc
P7:
1. 205
2. 205
3. Ground
4. Ground
5. 55.2
6. 5.24
NOTE: Set is outside where its 45-50 degrees. Green LED sequence has changed to ….- then after a while changer to …--
Dskall: I used a magnifying glass and can't identify any damage to chips or components.

[neutron561]

Re: 42" LG Plasma won't turn on

Reecey: That is a HeatSink? I have it off to try to get access to the module that has the 8 buttons. (no access yet)
Dskall: The wire from the button module to the main board has 1 blue wire and 7 gray. The blue has 3.2ish volts and doesn't seem to change when ON button depressed. pin 2 is 0 v and doesn't seem to change when ON button depressed. Other gray wires are 0 or 3ish v. I was originally leaning toward an open power button.

[neutron561]

Re: 42" LG Plasma won't turn on

Any tips on how to separate the plastic bezel from the glass screen without breaking anything?

[dskall]

Re: 42" LG Plasma won't turn on

Don't know what all proper voltages should be on each pin. Appears though that you have VA VS voltages. You've checked fuses on X and Y sus boards. Far left and right side.

[neutron561]

Re: 42" LG Plasma won't turn on

Don't know what all proper voltages should be on each pin. Appears though that you have VA VS voltages. You've checked fuses on X and Y sus boards. Far left and right side.

I think you are referring to the ZSUS and YSUS, correct? I do not see any fuses on those boards. On the ZSUS board, there is a printing called FS1 10A but it is just a jumper.
I only see 2 fuses on the whole set, one is 120VAC and the other has over 300VDC on it, both on the power board.

[vinceroger69]

Re: 42" LG Plasma won't turn on

c107 blue capacitor is thst just a black mark on the casing or a hole?

[dick_barton]

Re: 42" LG Plasma won't turn on

OK Dick, here’s todays readings for P6: (all volts DC)
1. 55.2 vdc
2. 55.2 vdc
3. 55.2 vdc
4. .016
5. .016
6. 17.96
7. 17.97
8. 0 GND
9. 0 GND
10. 3.29
11. 1.59
12. 1.49
13. .043
14. .021
15. 5.23 vdc
P7:
1. 205
2. 205
3. Ground
4. Ground
5. 55.2
6. 5.24
NOTE: Set is outside where its 45-50 degrees. Green LED sequence has changed to ….- then after a while changer to …--
Dskall: I used a magnifying glass and can’t identify any damage to chips or components.

I see the 5V, Va and Vs are present and correct. Is the -203V and +125V present.?

I'm not sure if P6 pins 11 - 14 voltages are correct so perhaps someone can advise.

[neutron561]

Re: 42" LG Plasma won't turn on

c107 blue capacitor is thst just a black mark on the casing or a hole?

Not a hole or burn. seems to be potting compound or some kind of dirt. It rubbed off.

[neutron561]

Re: 42" LG Plasma won't turn on

I see the 5V, Va and Vs are present and correct. Is the -203V and +125V present.?

I'm not sure if P6 pins 11 - 14 voltages are correct so perhaps someone can advise.

Where do I look for the -203V and +125V? I remember some high negative voltage on the YSUS side this afternoon. Should there be voltage on the tops of the caps?