LG 60PC1D 60 inch plasma tv no power

[tech2014]

When the set is turned on, the LED flashes blue then red, and goes into standby. I found an open 5W resistor, replaced it. I do not have the TV with me, just the 2 power supply boards. When I power up the boards, there is a click and the relays close and I am able to get the output voltages. The relays click again and the voltages go to 0 volts. I found that the VA voltage is very low, about half a volt.

Do I need to connect the boards into the TV for the VA to work, or is there a problem with the VA circuit. One person tells me it has to be connected to the TV, and another said its the VA cct. Any help is much appreciated

For reference, here are the power supply board model numbers
SMPS EAY32961901 and PFC/Standby EAY32961801.

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

To get Vs and Va, M5V must be present, and VS-ON must go HIGH.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

I know with some TVs you can shunt the PS_ON with a resistor so you can take the voltages. This P/S doesn't have a PS_On, only VS_On. is there a way to do this with the VS_On.

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

Does it have an RL ON or M5V ON?

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

It has RL ON .

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

So on this, that is your PS ON signal.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

So if I get 5v to the RL_On it should allow me to test the VA voltage?

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

Yes. Use a 100~470 ohm resistor in series to protect against over-current.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

do I use a low wattage resistor

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

1/4W or higher is fine

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

last question. I have a AC/DC converter that puts out 5v. Would this be sufficient with the resistor ? What about current draw?

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

You might as well use the 5V standby supply available on the power board.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

I forgot to mention that the 5v standby is 0V then the relay clicks and i get 5v. Then the relay clicks again & the standby voltage goes back to 0.
I put one side of the resistor on the STBY5V and the other side on RL_ON. I still get the same, relay clicks, all voltages accept for the VA come up for the few seconds the relays are closed, then back to 0 again. Doesn't this mean there is a problem with the standby circuit.

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

I don't want to sound silly, but I don't believe you. No standby, no LED... It might be on a pin marked STBY.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

I seriously don't have a constant 5v. I only have STBY5, no STBY. I also have a multi_On.

[tom66]

Re: LG 60PC1D 60 inch plasma tv no power

Yes but you won't be able to get that initial relay click without standby power, so it must be coming from somewhere.

[Clydeuk]

Re: LG 60PC1D 60 inch plasma tv no power

But surely if you have a standby led lit the main board must be getting the 5v standby supply?

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

I don't have the main board connected, only the AC/DC board and standby psu. The TV is 60" and too heavy so they just gave me the 2 smps boards. Could the voltage regulator for the standby 5v be faulty and thats why the relays click on and off. I get all the voltages except the VA when the relay clicks on then they go back to 0 after the relay clicks open again. The AC_detect also goes up to 5v when relays clicks then to 0v again. I have no boards with any LEDs to tell me if the standby is working, only thing I get is the clicking relays which tells me the stby 5v should be working.

In the service manual it says that the p/s waits for a signal from the micro on the main board, then the p/s powers up fully. Since I don't have the board I wanted to find a way to make sure it is actually fixed before returning to friend. Can I use an external 5v power source to get the board to power up so I can check all o/p voltages.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

OK I found that at a voltage regulator on the secondary side of the Standby board, with the power off, I have a reading of between 5.2-5.4 volts on the input. I also get the same on the gate of a mosfet . When I turn the power on and the relay clicks, the input of the voltage regulator moves to between 5.3-5.9V. The output is exactly 5v and the gate of the mosfet is 8.5V. I found 2 100uf electrolytic caps that both read between 125-128uf. The tolerance is 20% so a little off. I did order an ESR meter and should get it sometime this week so I will be testing all the electrolytic caps just to be safe.

If I don't find any defective parts, Since I do have voltage which moves around between 5.2- 5.4, could I jumper this voltage to the RL_ON so I can test the output voltages.

[tech2014]

Re: LG 60PC1D 60 inch plasma tv no power

Ok so I got all of my voltages other then the VA and VS. I now have the tv so I installed the power supplies and connected everything. I noticed that I didn't get any relay clicking but the power LED was on on the front of the TV. I noticed a large 10ohm 5W wire wound resistor was glowing and it got VERY hot. I removed the power immediately.
When I had all of the boards connected I still didn't get the VA or VS.

Does this mean there is a short circuit somewhere on the p/s? I never noticed the hot resistor until I put the connector from the Y sustain board onto the standby/pfc psu.