LG plasma 42pt350 relay just clicking.

[erickeri1234]

Hello everyone, I'm new to the site.
I have a LG plasma 42pt350 tv. It's from 2011, when powering on you can hear the relay click but then it turns off. So I looked for bad caps, didn't find anything. So I tried something else. I unplugged everything from the power board but the power cord going to it. The relay clicks faster when everything is unplugged from it. I'm very busy so I haven't been able to check more out on it. Can someone point me in the right direction.

Thanks E

[tom66]

Re: LG plasma 42pt350 relay just clicking.

Do you happen to have a digital multimeter, and a camera to take pictures?
Could you take pictures of the chassis layout so we can see what the board layout is like.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

I do have a digital volt meter and I will post a picture.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

updated with pictures.

[dkneyle]

Re: LG plasma 42pt350 relay just clicking.

Read my post here: https://www.badcaps.net/forum/showthread.php?t=37125

I think it will help you.

[tom66]

Re: LG plasma 42pt350 relay just clicking.

OK in this (upside down) picture
https://www.badcaps.net/forum/attach...1&d=1400982012

Right board is Y-sustain
Left board is Z-sustain

Y-buffer connects to Y-sustain which connects to plasma panel orange ribbons.
Z-sustain connects directly to plasma panel. Z-sustain chains power to Y-sustain.

Please disconnect the Z-sustain power, but leave all other connectors hooked up, and confirm if the relay continues to click, or if it clicks only a few times then stops. (No picture should appear on the plasma panel.)

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

The relay clicks faster when I disconnect everything but the power going to it. Without me touching it, just when I plug in the power cord.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

Update
I did a little more testing/looking at the TV.

With everything plugged in I get 3 relay clicks.
First relay click red light flashes(red light on) then it starts to fade out, once out relay clicks again red light still is off. then relay clicks again and red light comes back on. Its like it turn on. then off, then goes in stand by mode.

I disconnected the y-sus cable from the z-sus board and there is no difference. 3 relay clicks.

I even disconnected the power going to the z-sus board and I get the same 3 relay clicks.

When I disconnect everything but the power in going to the power board the relay clicks faster and it doesn't stop, the relay clicks about every 4 seconds.

[dkneyle]

Re: LG plasma 42pt350 relay just clicking.

Here's a few YouTube clips that might help: https://www.youtube.com/watch?v=_UyXfxG5LyE That's the typical caps that fail - typically you'll notice if they have bulged tops and some black electrolytic gunk coming out.
https://www.youtube.com/watch?v=I9wF0OLyV0k This clip and the (second part clip) describes the typical active and passive components that fail.
Given that you have disconnected y and X Sus boards I think we can assume it's a power supply failure.
(I'm putting money on that regulator device!)
Don't be too concerned that your power supply board is not exactly the same. Similar sets will have very similar circuits for the SMPS with some minor variations.
Let us know how you go.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

I've charged tons of bad caps before. These caps look very good, But there are 2 that look pushed in. not sure what the means. these are the NXB 50v 220uf location c365 and c377.
Im thinking the samething, the voltage regulator.
Im going to test the diode and the resistor he pointed out in the video.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

Well I tested some diodes and found 2 of them bad. One is reading .213 and the other one is just plan shorted.
The one that is shorted is marked VA9 IN5408
The other one is SR104 that one is reading .213

I replaced the shorted one but I didn't replace the SR104 ( cause Im not to sure if it is really bad) But Im still getting the same clicking relay.

[dkneyle]

Re: LG plasma 42pt350 relay just clicking.

When diodes go I always question what it was that stessed them out. Without delving into your particular circuit, that SR104 is often used as a type of snubber diode in conjunction with a cap and sometimes a resistor. The associated cap sometimes goes bad.
Have you measured the SR104 out of circuit? The associated components can sometimes give strange readings. It is a high speed diode. Should read typical 0.6V I think? Look it up on the net, but I think it's 40V 1A. It has to be high speed (I mistakenly replaced one with a conventional power diode and the switching MOSFET complained by overheating badly.) I canabilised one fom another SMPS - higher value but did the job OK.
I think you are certainly on the track of your problem.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

Yea I tested them in circuit and then out of circuit. Sr104 reads the same in and out. Now I'm just stuck not sure what to do next

[dkneyle]

Re: LG plasma 42pt350 relay just clicking.

I looked up the specs for that SCHOTTKY diode and it is as I thought, 40V 1A. And its bias voltgae is stated as being .55 volts. So if you are getting only .213 then I think you can assume it's damaged. I'd also look at the MOSFET that is usually somewhere around that vicinity. Often the diode sits across two of the MOSFETS legs. Use the diode function on the meter and see if there appears to be direct shorts across any legs of the MOSFET. I'd put money on the MOSFET being dead as well.

[tom66]

Re: LG plasma 42pt350 relay just clicking.

.55V for the diode will likely be at 1A rated current, your meter will test at 1mA so the Vf will be much lower (the forward voltage of a diode is related to the natural log of the current, so doubling current != double voltage but rather some complicated equation.)

[dkneyle]

Re: LG plasma 42pt350 relay just clicking.

He knows his stuff our friend Tom! (I have a Fluke digital meter that I've owned since I started as a trainee technician in 1978. Best investment I ever made. The diode test function on it seems to magically get the forward voltage value right in most cases - maybe it puts a bit more juice through? For example, it will light an LED, and I assume that would need 20mA at least?)
The question about that diode is whether it has current flow one way and infinite resistance the other? If it does, then it's probably OK. Not sure of Tom's experience; my experience is that they either go short or open, no 'half measures'. (Or explode and vanish off the board - but I guess that's still open circuit!)

[tom66]

Re: LG plasma 42pt350 relay just clicking.

Oddly, an LED will visibly glow from about 50~100µA. Not brightly but visibly. An LED will glow reasonably brightly at 1mA. Light brightness as perceived by humans is also strongly logarithmic. An LED at 10mA is only about 2~3x brighter as the human eye sees an LED at 1mA.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

The mosfet, That will be the str w6053s? I was check looking that up at digikey. If that is it how can I test it? I never tested a mosfet. Diodes, resistors, etc.

[erickeri1234]

Re: LG plasma 42pt350 relay just clicking.

O I have fluke 115. I do need to get an esr meter for caps.