LG42PT350R clicking and doesn't turn on

[buchman]

Hi,

I checked all the capacitors on every board and they are fine.
All diodes are fine too.
Checked all the resistors and didn't find anything bad.
The fuses are good.
No picture and no sound.

I have noticed that when the power board isn't connected to anything ecxept electricity, it shows the VA and VS as noted but, as I connect the YSUS, ZSUS, main board or the T-CON, the VA and VS drops to less than 1 volt on the power board.

Is the VA and VS should always stay on their values?

Thanks in advance,
Edward.

[wills123]

Re: LG42PT350R clicking and doesn't turn on

You connect each one in turn and the voltages drop? Or all of them?, try to connect all but the x an y then see if the voltages still there, test for short circuit on x an y between vs and ground for a starter

[buchman]

Re: LG42PT350R clicking and doesn't turn on

If I connect only one of the above boards to the main board then the VS and VA drop. How do I

[Hamie]

Re: LG42PT350R clicking and doesn't turn on

Depending on the model, if an error is detected the mainboard will stop sending then vs-on signal.

Alternatively it could be failing under load.
You can solder in a 200w (or 2 x 100w in series) light bulbs between vs and ground. The bulb should stay lit, if it flickers or turns off you may have a problem with your power supply.

What are the vsc, -vy and z-bias voltages.

[buchman]

Re: LG42PT350R clicking and doesn't turn on

If I disconnect the main board and, let's say, only the zsus or the ysus connected, then the vs and va also drop. I mean that even if the main board is disconnected, the vs and va drops if I connect anything beside the power supply board.

Please guide me how do I check the VSC, VY and z-bias voltages?
I have a digital multimiter and the understanding, just need some guidelines.

Thnk you so much guys.

[Hamie]

Re: LG42PT350R clicking and doesn't turn on

If you disconnect the Main board the power supply is not going to turn on.
The main board sends the signal to turn the power supply on and off.
The power supply would need to be 'jumped on' if you disconnect the main board.

Vsc, -vy test points are on the y-sustain. These are sometimes measured across a marked resistors.
Z-bias is on the z-sus.

[Hamie]

Re: LG42PT350R clicking and doesn't turn on

Z-bias is measured across this resistor, put your probes to the corresponding + and -

You don't have a clear picture of the y-sus so I can't see the other test points, but they will be similar to the z-bias.

I recommend putting back in the screws so it's properly grounded.

Remember that your vs and va are dropping so you'll need to quickly test these points before they drop off.

[buchman]

Re: LG42PT350R clicking and doesn't turn on

Hi,

Tested for Vs and Va and it shows a few milivolts (put the probes on and then turned on the TV).

Tested the Z-bias and Vy and they show a few milivolts too.
Didn't find the Vsc test point.

Didn't try to solder 200W light bulb.

Bridged the EXT_AUTO_GEN (with main board disconnected) and didn't see any test patterns.

P.S. I have no light (green or red) on the T-CON or the main board (I don't know if there should be at all)

What should I do next?

Thank you very much guys.

[vinceroger69]

Re: LG42PT350R clicking and doesn't turn on

i think if possible you need to check the psu voltages first im not sure how to force on this psu maybe hamie can advise.

[buchman]

Re: LG42PT350R clicking and doesn't turn on

Hamie? Tom? Anybody can guide me what to test next?

[ReeceyBurger123]

Re: LG42PT350R clicking and doesn't turn on

Checked Vs on signal ?

[buchman]

Re: LG42PT350R clicking and doesn't turn on

Checked Vs on signal ?

where do I check it?