LG 50PX4R-ZB stuck in standby mode

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

On the power supply.

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

I measured 19v and GND and it only measures 0.008 mV DC Should i measure in DC or AC ?
thanks

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

DC. Do you see any other voltages that are measuring low?

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

DC. Do you see any other voltages that are measuring low?

yes they are all low except STBY 5V and AC ON

AC ON = 4.338v
RL ON = 0,0037v
STBY 5V = 4.97v
Vs ON = 0.038v
5V MONI= 0v

19v = 000.8mv
19v = 1.3mv
6V = 0.1v
3.4v = 0.464v

Do you need me to take any other measurements ? thanks

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

When you press the power button, or turn the TV on using the remote, do RL ON, VS ON or anything else change?

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

When you press the power button, or turn the TV on using the remote, do RL ON, VS ON or anything else change?

RL ON goes to 4.25v when power button pressed then back to 0.037v

The rest the same ?

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

Did you note that with your old board? Because that indicates power supply not working? Did I miss something?

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

Hi Tom

RL ON = 0.04V DC then switch power button on remote then 4.23V DC then back to 0.04 V DC after 10 seconds

Vs ON = 0.04V DC switch on power on remote still 0.04V DC

Thanks

It looks like you have a main board fault as it's never switching on the VS ON.

yes i did these checks before ?? and the same readings ??

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

I am not sure if your power supply or main board is bad now. RL ON should cause the output voltages to come up, but you are not seeing them rise? On the other hand, the power supply might be waiting for VS ON before turning on the outputs fully.

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

I am not sure if your power supply or main board is bad now. RL ON should cause the output voltages to come up, but you are not seeing them rise? On the other hand, the power supply might be waiting for VS ON before turning on the outputs fully.

OK So the output voltages i presume go from the power supply to the main board then back to the power supply on the 19v gnd pins connector ??

But there is a possibility like you said that the power supply board is waiting for a voltage at vs ON before turning the output voltages to the main board ??

The main board does have a red led light on it ???

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

Do you think it will be a power supply replacement or do you think it may be repairable ?? I cant see any indication of badcaps though??

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

The power supply produces the voltages, which come up at those outputs.
Do you hear a relay click when you press the power button?

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

The power supply produces the voltages, which come up at those outputs.
Do you hear a relay click when you press the power button?

Yes .... when the tv is first powered up then by pressing the power button on the remote.

If i try pressing the button on the remote again it does not click ONLY when unplugged and plugged back in ??

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

do you think that this indicates a faulty power supply thanks

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

I am not certain, but I would try that next. Unfortunately it is difficult to be certain.

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

OK thanks for your help tom .... do you think it could be a capacitor problem ... ive heard that sometimes a bad cap might still visibly look ok ?? ive bought a new impedence meter but only goes to 2000uF

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

I would not expect so. With bad caps you'll typically get an output voltage but it will be lower or higher than it should be.

[surferbum]

Re: LG 50PX4R-ZB stuck in standby mode

OK so i need to replace the power supply board ?

I will have to try and find one !!

Thanks again

[tom66]

Re: LG 50PX4R-ZB stuck in standby mode

Can you return your main board?

[tw2005]

Re: LG 50PX4R-ZB stuck in standby mode

Tom, this set appears to use the same ysus,zsus as the 50PX5D. I'd have a closer look for shorts, blown fuses or symptoms on those boards and IPMs.

The initial post symptoms sounds like it could be protection mode. I don't remember all the ins and outs of the couple I had but sounds similar and I know on those you'd get a click , LED would change then back to standby in about 10secs.

IPMs replaced on both Y & Z got that junker going again and a bad Ysus was burning up resistors on the Z.
Horrible TVs to work on, the LG Fallas TV trainig guide would be close to this, but the translation to english makes the flow charts near impossible to understand.

There's a note , Unable to check voltage when disconnecting Ysus due to 50" protection?