Lg 50pz550

[migimara]

Hello all I bought this TV off this guy for $200 on Craigslist who stated that the tv would click on then turn off. I've read on this forum about the z sus board being the issue so I ordered the part and replaced it but the problem was still there.

I read a bit more and tested the capacitors on the original board and it seems like the z sus board was good after all.

I noticed as I turned on the tv, it would click then the speakers I believe would Make a hissing noise then click off. I've gone ahead and unplugged the wire connecting from the power supply board to the y sus board and turned on the tv again, this time it clicked on and I guess it appeared to stay on with no picture. I then used the remote to power off the tv and it seemed to power off since it clicked.

Now I bought a new y sus board and power supply board since for the life of me could not find any blown capacitors and would like to know what y'all may think may be the problem. Thanks!

[capkid]

Re: Lg 50pz550

Board swapping without proper diagnosis can get expensive. Do you have a digital multimeter? You'll want to check the power supply VS and VA output voltages.

[freakaftr8]

Re: Lg 50pz550

Could be a shorted ipm on the ysus. The big ic under the heat sync.

[capkid]

Re: Lg 50pz550

Could be a shorted ipm on the ysus. The big ic under the heat sync.

I don't believe this TV has IPMs.

[migimara]

Re: Lg 50pz550

Just wanted to update. Power supply board hasn't came yet but the y sus board did. I replaced the y sus board and attempted to turn on the tv again with the back cover off. I turned it on and it seem to have worked until I saw a spark from the Z sus board and the tv turned off. It is now repeating symptoms. Did I fry something? Also how would one go about checking proper voltage output? I do have a multimeter and would to check things out before it gets pricey..I can already feel like I may have to replace the y and z sus boards again.. Thanks!

[capkid]

Re: Lg 50pz550

Hmm, not sure. I'd repeat your original test by disconnecting the Y-Sus and Z-Sus to see if the power supply stays running. Check the VS and VA output voltages on the PSU. I'm not sure how experienced you are with a multimeter:

(1) Set your meter to the DC voltage setting ("V" with a line above it).
(2) Touch the negative probe to chassis ground (use a metal part of the back of the panel as ground) and the positive probe to VS and VA test points. The test points are jumper wires on the board that are labeled as "VS TP" and "VA TP" at locations J101 and J102.

[migimara]

Re: Lg 50pz550

Went ahead and disconnected the z sus and y sus board. Tv stays on. Connected the z sus board tv stays on. Connected y sus TV clicks on and off. Where would I check the vs and va output on the pus?

[capkid]

Re: Lg 50pz550

Went ahead and disconnected the z sus and y sus board. Tv stays on. Connected the z sus board tv stays on. Connected y sus TV clicks on and off. Where would I check the vs and va output on the pus?

I just updated my last post.

[migimara]

Re: Lg 50pz550

I just updated my last post.

Thank you very much! Just tested the va and vs and I get nothing. Maybe a spike to 3.5 volts but nothing other than that. Safe to assume this board is bad?


Edit

Nvm it seems like it wasn't on when I was testing. Va tp I get about 54/55 volts and on the vs tp I get around 201 ish never exceeds 203

[capkid]

Re: Lg 50pz550

Did you test the VS and VA voltages with the TV turned on?

[migimara]

Re: Lg 50pz550

Yea I edited last post. Get around 54 for va and vs 199. It never exceeds 199 though the panel says setting should be 203 v.

Edit

I think I may have found some thing wrong. I took the multimeter and tested where the y sus board connects to the psu board. Tested both the VS jumpers and noticed a big spike in voltage before it comes down to 199/200. Is this normal? I know when testing the test points the voltage doesnt spike so I was wondering if they're related in any way.

[capkid]

Re: Lg 50pz550

The VS is slightly low, but it's not so low that it should cause the types of issues you're experiencing. I'm assuming the VA matches the panel label. I'd try connecting the Z-Sus to see if the VS and VA voltages change. I'd then check the Vzb voltage on the Z-Sus to see if it's within spec; Vzb should be the last voltage listed on the panel label.

[migimara]

Re: Lg 50pz550

I edited my previous post. But to add on, seems like I can't test z sus without the y sus, since the z board is connected to the y sus board.

[capkid]

Re: Lg 50pz550

I edited my previous post. But to add on, seems like I can't test z sus without the y sus, since the z board is connected to the y sus board.

Ah, ok, that makes sense. I was confused by this post:

Went ahead and disconnected the z sus and y sus board. Tv stays on. Connected the z sus board tv stays on. Connected y sus TV clicks on and off. Where would I check the vs and va output on the pus?

Did you try connecting the Y-Sus to the PSU without the buffer board being attached?

Note: You'll have to give the Y-Sus time to discharge before re-connecting the Y-buffer to the Y-Sus after you've finished your test, or you could see sparks and possible damage. Use your multimeter to check the voltage at the connector to judge when it's safe to re-connect; under <1V is usually what I wait to see. I sometimes force a discharge using a high wattage resistor or light bulb in a socket, but let's not go there for now.

[migimara]

Re: Lg 50pz550

I think I may have found some thing wrong. I took the multimeter and tested where the y sus board connects to the psu board. Tested both the VS jumpers and noticed a big spike in voltage before it comes down to 199/200. Is this normal? I know when testing the test points the voltage doesnt spike so I was wondering if they're related in any way.

Spikes to around 600v and 300v

[capkid]

Re: Lg 50pz550

I think I may have found some thing wrong. I took the multimeter and tested where the y sus board connects to the psu board. Tested both the VS jumpers and noticed a big spike in voltage before it comes down to 199/200. Is this normal? I know when testing the test points the voltage doesnt spike so I was wondering if they're related in any way.

Spikes to around 600v and 300v

That's not normal, and I'd guess it's an issue with your meter. I'd expect some fried components with actual voltages that high.

[migimara]

Re: Lg 50pz550

Seems like I blew the y sus board I originally bought. The new psu board that came today seems to be having the proper voltage. The spikes I was getting before aren't happening anymore. Tried powering on the TV without the y buffer boards attached and its still clicking on then off.

I'm completely stumped now.

[capkid]

Re: Lg 50pz550

Did you try disconnecting your Z-Sus? I remember you mentioning that you saw a spark there earlier.

[migimara]

Re: Lg 50pz550

Yea I tried disconnecting that too, same result.

[migimara]

Re: Lg 50pz550

Ok another update. Replaced the y sus board again and it appeared to turn on then it popped again coming from the z sus board.. Any ideas? Could the buffer boards be acting up? Cuz I'm completely out of ideas