2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main CPU

[bffargo]

LG 60PB66550 NOV 2014
PSU: EAY63168603
PCB: EAX65359531 2013.11.01 Rev:1.0

Main board: EAX65399305(1.0) 13.11.27 PU42A/PA42A/PD42A

Symptom:
While watching, just went black and started clicking relay every few seconds.

Initial diagnosis:
Removing JUST the main CPU/Input PCB from circuit stops the clicking. No problems with any other boards/drivers. (Removing all other boards and only putting Main back in is all it takes to start clicking again)

Deeper diagnosis:
Pulling pins #1/#2 (Blue/Grey) from the connector housing at the power board connector P813 (17V pins), allows main board to be reconnected either alone or with all other boards, and then does not click. Screen even lights with very dim green pixels as it had normally with otherwise black screen.

I pulled all electrolytics from power board and test fine with cap tester with low ESR. No bulging of those or any of the blue rectangular caps (which have not been pulled or tested yet).

There is about 10.2 ohm resistance between the 17V line and GND on the mainboard testing it when pulled from set. There is exactly 16.88 V (no load) at the pin on the power supply when it is disconnected from the mainboard.

Questions:
Is the issue a short in the main logic board or a problem with a weak 17V rail on the power supply? I spot checked transistors on power board in circuit with diode check on DMM and didn't find any obviously shorted. What use is the 17V feed as compared with the normal 5.2V rails?

Would a new main logic board fix the problem or is it something else?

Thanks much in advance!

[bffargo]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

Additional tests:
After getting the main board back in a more normal state apparently, with the 17V leads pulled from the connector, now it will turn on with remote with quick flash of grey screen, then turn off, then turn back on by itself a few seconds later and stay on with a black screen (very faint green pixels seen in dark room). After this point it stays on without the 17V connected.

If using the remote I turn it off, wait a few seconds and then turn it back on; then it resets to turning on for a few secs, turning off, then turning back on and staying on again. But in all cases there never is a picture, no buttons on remote bring up any OSD or anything.

I found some 2010 service manual info for an older LG Plasma, and it seems the 17V rail is used by the audio amp on the main board. As soon as I connect that back up, either through the connector or jumpering using a DMM in 10A current mode, the relay will immediately turn off the set. So it definitely seems the primary failure is a short somewhere on the main board in the audio section. I tested the speakers and they ohm out at just under 8 ohms, and didn't see any other obvious visual / smell problems by the audio amp and inductors immediately before the speaker connector.

I'm prepared to buy a new main board if that is ALL that I need. But I want to be sure it's just an issue on the main board and that it won't be something else. It seems like just a short on that one line though not entirely sure how the power on test is running and why it shuts down once then reboots and stays on now after 17V is pulled. It might just be normal, but hope there isn't some other issue there that's not on the main board. All other test points for voltages appear good and nothing shorted on the side panel driver board connectors.

Thanks for any additional ideas here to confirm just a mainboard/audio amp short or something wider and not worth replacing just the main board.

[nomoresonys]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

correct you are, with these plasmas one bad board can and prolly will knock down other boards, not sure how you checked the y buffer boards, I would check those then maybe all the transistors on the heatsinks of y board and x/z board and all the diodes and resistors of course, good video there testing y and y buffers, be sure you are on ground when checking for shorts on those y buffers: https://www.youtube.com/watch?v=Nt0ARKkXC5I

[diif]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

It's an LG, you should be able to disconnect the mainboard, jumper a couple of pins on the logic board and when powering on the TV, it should display test patterns.

[bffargo]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

It's an LG, you should be able to disconnect the mainboard, jumper a couple of pins on the logic board and when powering on the TV, it should display test patterns.

Thanks a lot! I found this similar thread: https://www.badcaps.net/forum/showthread.php?t=63132 and performed the same disconnect of the LVDS (P231) and then jumpered across the via's under R651 / R652.

The unit now turns using the remote and started a Red then Green screen, turned off after a couple seconds, then back on by itself and stayed on (due to of course still having the 17V line to mainboard pulled so it can even start).

The panel went through all of the RGBW, horiz/vertical gradient sweeps and then bright white bar h/v sweeps just fine and repeated until I manually shut it off finally. The entire panel and drivers seem to be 100% working as expected based on other symptoms.

Does this mean that it only is the main CPU/Input board that is the problem loading down the 17V line and a new one should just fix everything? Since 16.8 V is being put out on the PS pins it doesn't seem like any problem there, just a short on main board?

[Biruslapio]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

The 17V that goes to the logic board is produced by the Y-SUS, it's not your problem, it must be the mainboard, unplug the mainboard from the power supply and the tv will auto start when plugging in AC and never turn off if the other boards are working, if that happens, mainboard is at fault.

[diif]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

Thanks a lot! I found this similar thread: https://www.badcaps.net/forum/showthread.php?t=63132 and performed the same disconnect of the LVDS (P231) and then jumpered across the via's under R651 / R652.

The unit now turns using the remote and started a Red then Green screen, turned off after a couple seconds, then back on by itself and stayed on (due to of course still having the 17V line to mainboard pulled so it can even start).

The panel went through all of the RGBW, horiz/vertical gradient sweeps and then bright white bar h/v sweeps just fine and repeated until I manually shut it off finally. The entire panel and drivers seem to be 100% working as expected based on other symptoms.

Does this mean that it only is the main CPU/Input board that is the problem loading down the 17V line and a new one should just fix everything? Since 16.8 V is being put out on the PS pins it doesn't seem like any problem there, just a short on main board?

You need to do the test as detailed, plug the 17v line back in. It identifies if the mainboard is at fault.

[bffargo]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

You need to do the test as detailed, plug the 17v line back in. It identifies if the mainboard is at fault.

When the 17V line is reconnected to the header leading to the mainboard, the power supply relay just clicks repeatedly. Removing the 17V line or the entire main board completely stops the clicking.

[bffargo]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

Tried again with LVDS disconnected but everything else connected (and the jumper installed) it turns on, then immediately turns off after using remote each time.

Removing main board power cable at that point, then it turns on automatically and runs through the RGB+wipes.

Putting back in the main board cable it now is no longer clicking (even with 17V connected), just turns on after using the remote then turns itself back off, regardless of jumper or LVDS connected. It seems it's now locked in a default OFF setting vs the default of ON it apparently was in before I pulled the 17V since it started failing when it was on initially (which caused the repeated clicking cycles trying to go back to On mode always after power loss which it no longer has to)

This seems all main board related at this point and nothing else?

[nomoresonys]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

pretty straight forward test for auto gen, unplug mainobard from powerboard, and unplug mainboard from control board, put in jumper on control board, plug in tv. Another fine how to example there from Nick's tv: https://www.youtube.com/watch?v=6oYj1B86y0s

[diif]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

This seems all main board related at this point and nothing else?

Yes. The self test confirmed it.

[bffargo]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

Yes. The self test confirmed it.

Received replacement main board today, swapped it in and everything works 100% so far (30 minutes) Thanks all for the double check confirmation and tips and links.

Does anyone put in a small quiet fan in these to reduce the heat from the heat sink? Or does that just lead to more problems like dust clogging vents? It felt sufficiently warm with back off. Still touchable though.

[diif]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

Nice work, I wouldn't worry about a fan, it's lasted 8 years without one.

[nomoresonys]

Re: 2014 LG 60" Plasma shut down just clicking unless I disconnect 17V line to main C

It'a a plasma, they run hot, obvious tip, heat kills and shortens the life of tvs, anything you can do to keep it running cooler is a PLUS. so a fan hooked up properly is not a bad idea.