HELP!!! LG 50PN4500 plasma. Voltage issue.

[Mel0317]

I am having an issue with z sustain board. The T.V. doesn't want to turn on. I tracked it down to a problem with the z sustain board but I am having issues finding which component is bad.

The high voltage going from z to y is good but there is 17 volts that goes to y that only reads 3 volts. I have pulled all electrolytic and all brown film capacitors and tested them with a capacitance meter. And all are well within tolerances.

Any ideas on where to go now? I would much rather replace a component than replace the whole board.

[Hamie]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

You probably have a faulty y-sustain.
YSUS needs to be working perfectly for voltages to be accurate on this model. Took me hours to work out what was wrong with the several dozen of these and similar models that share this YSUS.

Take a picture of your YSUS.

[Mel0317]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

I'm not sure if the image is going to post. But the ysus is good. It is brand new. I replaced it before I did any voltage testing. The pin from the xsus that is supposed to carry +17v to the ysus is only putting out 3 volts. And there is a jumper further down the zsus that is labeled 18v that only puts out 3. And I know there isn't a problem with the power supply board because all voltages leaving the power supply are perfect.

[Hamie]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Put you meter in ohm.

Under the 2.2 ohm resistor (red red gold gold) you'll find a surface mount cap.

Test it, if its shorted it needs to be replaced. I used a 22nf
As a replacment.

Let us know how you get on.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Mel0317
Did you end up resolving this issue? I have an LG 50PN4500 that has the same voltage coming from ZSus as yours did and my logic board has no lit led on it either. I was leaning towards a new main board? I am going to check the surface mount cap under the resistor in the morning as it is late here. Let me know thanks.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

I was curious where on the tv and which board this picture is of Thanks for your time

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Mel0317
Does your YSus have a ticking noise coming from the area on the bottom right where the yellow transformer is?

[dick_barton]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Post #3 has the picture of the circuit board and Hamie has referenced the 3 resistors grouped together in his post and said check capacitor underneath the red, red, gold, gold resistor.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

The power supply is showing a short on the VSTP where it should be reading 205V the VATP is reading 55V which is the right voltage. I believe the problem is my power supply, when I disconnect the Y Sus I have audio but no picture, when I diss connect the ZSus it disconnects the YSus at the same time, I still have audio with no picture. If I leave all boards connected then I still have normal on/off and audio with no image. Should I test this IC under thes resistors or is it on the underside of the board? If so how do I detach the ribbon cables safely? Thanks for your time.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

This is the location of the clicking noise.

[dick_barton]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Have you checked the capacitor as suggested by Hamie?
You can check the Q202, D202, D206 without removing the board. Use your meter set to diode mode and ensure that the set is powered down and disconnected from the wall socket.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Q201=513
D202=515
D203=526
D204=521
D205=523
D206=486

Should I replace D206? Or is it withing tolerable limits? I think it might be my power supply? When I diss connect the Z & Y Sustain boards my VS is still shorting on the pin out to the Z Sus? I am new to this. I am not sure if "Hamie meant that the Y and Z Sus need to be connected in order for the power supply to have proper voltages?

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Please let me know thanks

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Ok first picture is of PSB to Main board, second pic is of test results not sure if the voltages are to spec or not? Curious though when I test the VS on the two pins in the 3rd picture and they short when the black probe is attached to the chassis, but when I touch the black lead to either one of the two heat sinks on the left I get a voltage from the VS PINS (pic 3) in the 20 to 30 volt range fluctuating.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

First pic

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

2nd pic

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

3rd pic

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

4th pic. I am not entirely sure why I couldn't upload more then one pic per post but I suppose it's ok.

[Logen1]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

Ttt

[heavymachines]

Re: HELP!!! LG 50PN4500 plasma. Voltage issue.

When u go to manage attachment and you click on attach then click attach again under the first one u clicked and attached with and keep on going...