LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

[kca]

Hello all ~

I picked up a nice 2014 LG 60" plasma the other day and it has the relatively common problem of the cyclical clicking on the power supply. I have been trying to isolate the problem but could use a little help in doing so. I have been taking some notes on my progress and will post those soon along with some pictures. Just wanted to get this thread started for the moment.

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

LG 60PB6900 ~ 60” Plasma (2014 model)

The Problem: Upon plugging in the power cord, get a cyclical, repeated clicking emanating from the power supply with the red LED on the front panel turning on and off in concert with the relay switch clicking.


Testing of PSU Voltages:

Connector that leads from PSU over to the ZSUS (located in the upper-right hand corner of the PSU):

VS was on the PSU was initially at 215 ~ I dialed it down to 205, where it was supposed to be.
VA was right on at 55
5V, labeled as M5V on the board itself, was as expected and sitting at 5.1

Exact readings, after I made the adjustment, were:

205
205
0
0
55
5.1


Connector that leads from the PSU down to the Main Board (located in the lower-right hand corner of the PSU):

Everything seems to be in order here too.

Exact readings were:

3.2
3.2
5.1
0
0
5.1
5.1
0
17.1



[B][I][U]TESTS ATTEMPTED TO ISOLATE WHICH BOARD IS AT FAULT:

When EVERYTHING is connected ~ Cyclical, repeated clicking

When the connector from the PSU to the Main Board is pulled at the top of the Main Board ~ Only one click

When everything is in play, including the Main Board, but the ribbon from the Main Board to the Logic Board is pulled at the Logic Board itself ~ Cyclical, repeated clicking

Note: Highlighted this section because the pattern seemed a little fishy to me.



When everything is connected except the ZSUS, meaning I pulled the connector that leads from the PSU to the ZSUS at the ZSUS itself ~ Only 1 click

When the connection between the ZSUS and the YSUS is broken (by unplugging the connector at the top of the ZSUS) ~ Only 1 click

Everything connected except the YSUS ~ Only 1 click




* Baked the Main Board on the evening of Monday, August 5th. To no avail. Nothing appears to change, indicating that the Main Board is not the likely culprit here. Did this just because so many of the LG's I've worked on of late have had Main Board issues that were easily resolved by the reflow.


* Test to see if I could produce a test pattern by bridging R651 and R652 on the Logic Board produced only 1 click and NO picture and/or test pattern (as kind of expected, because the Main Board was disconnected from the PSU for the purposes of this test). And, given the fact that there is no direct connection between the PSU on this model and the Logic Board itself. Performed this on Tuesday, August 6th.

Note: when the same test is performed, with the Main Board connected up to the PSU this time, but the Logic Board disconnected from the Main then I do get the repeated clicking (as mostly expected).


* Tried heating up the PSU with a hairdryer ~ to no avail. Didn't seem to change anything, although I did not keep it on there extremely long. Tried to hit all of the mosfets, though, and get them heated up to the potential point of change.

There is no green LED indicator light showing up on the Logic Board. Haven't seen one yet, through any and all of these tests. There does NOT appear to be a light built into the board at all, though I could be wrong about this.

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

And some more photos that focus in on the Logic Board. If the Power Supply Unit is not the culprit, could it be that the Logic Board is faulty given the tests I have conducted and outlined above?

Apologies for all of the 90 degree rotated photos and the upside down one as well. I'm still not sure why half of my uploads are correct and the other half are askew. If anyone has a clue, let me know how to remedy this.

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Dissconnect the cable between the Main board and the control board, Then connect the two points on the control board labeled EXT_AUTO_GEN and plug in the tv, you should see the screen run through a series of tests. If this works the fault is on your main board.
The LED on the control board is D101 near P105

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Thanks. I do see the location of the LED now on the Control Board. Still have not seen that light up, however, in any and all of my tests.


As far as the Auto Gen test, I already performed that and there was no change. That's the R651 and R652 reference I made up above in Post # 2.

I did it twice, just to be sure. Once with the Main Board disconnected from the PSU (with the result being 1 click only, as somewhat expected as that followed the general pattern), and the 2nd time with the PSU and the Main Board still connected (with that result being the repeated clicks, also primarily expected).

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Q: Does the fact that I am getting NO green light on the Logic / Control Board at all, under any scenario I've tested so far, .... coupled with the fact that the PSU seems to be generating correct voltages, ..... and in addition the clicking relay sound remains even if I isolate this Logic / Control Board


ALL lead to the probability that it is a faulty Logic / Control Board?


Or, is it not likely that simple?

If so, they are only about $25 and probably worth the cost to swap out and try. Though I would rather be sure that I have eliminated all of the other boards as possibilities first.

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

I have seen another test for the same control board on a 50PB5600 but I have never used it

After disconnecting the tape between "Main" and "Logic" and shorting Pin 1 and Pin2 of the P222 connector on "Logic" LED D101 flashes in the sequence: long, short, long, short, break etc.

In this case the person replaced the Y-sus and it fixed the problem

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

I'll give it a try.

The connection between the PSU and the Main stays intact then, during this test?

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Just tried it. No change to the pattern. With the Logic board disconnected, it still produces the cyclical, repeated clicking on the PSU relay .... even with Pins 1 and 2 on Connector 222 bridged.

Note: Tried Pin 1 and 2 from the left and, just in case, also tried the first two pins on the right hand side of that same 222 connector. Same results each time.


No lighting up of the Logic LED whatsoever.


{Of particular note, in this tv's configuration, there is no direct connection (meaning, no ribbon cable or wires) between the PSU and the Logic board itself. Is that important re: this latest test I've performed, in that the only ribbon leading into the Logic board is the one coming from the Main .... the same one I am DISconnecting in order to perform this test?}

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

I'm not 100% but I believe the control board gets it's power (+5v) via the Ysus connector, not sure which pin but I see a +5v on P222 Pin12, so check if it is there. It might also come via the Z-sus and down to the X-drive boards and up one of the flat cables.
Pin #1 should be marked with a ►

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

You are absolutely correct, R_J. Just tested it.

Pin 12 does read 5.1V. Of course, when the tv is cycling and the clicking is going on, the 5.1 is similarly dropping to about 0.3 and then back up to 5.1 again, in repeated fashion. This happens every two or three seconds in sync, of course, with the clicking.

When I disconnect the Main from the PSU (at the PSU connector in the lower-right hand corner of the Power Supply), thereby eliminating the relay clicking, then the 5.1 at Pin 12 at Connector 222 on the Logic board stays stable.

So, as you said, it must be feeding in from the YSUS. Or, through the ZSUS to the X-Boards and back up, as you also mentioned. I did not know it could come in from the "backside(s)" this way. I thought it always was fed in from the Main. So, thanks for teaching me something new.

Its presence seems like an important clue. Where do we go from here? What do you think is inhibiting the green LED from flashing on this Logic board?

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Any further insights or next steps?

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

You could check if there are any shorted fets on the Ysus board, You could also try unpluging the upper and lower buffer boards from the Ysus and see if the Vs voltages stays up and no clicking. without a scope to check if there is drive coming from the control board its just guessing.

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Will do those 2 things. Would be so nice if there could be an indicator light on each of these boards. Two on each, in fact, would be nice. One coming in and one going out to immediately indicate whether the power is flowing through properly.

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Getting back to this repair. Did a little more research online and found this great video:

https://www.youtube.com/watch?v=oMi76UoIkbo

Tested my Ysus in the same way that he did on the video and the result was exactly the same (shorts on the 2 Vs pins were found on this Ysus connector). So, I am almost positive now that the fault lies on the Ysus. Going to do more component testing on the Ysus now. I have not been able to find any fault on the two buffer boards, so I think it is indeed isolated on the Ysus itself. If anyone has any further insight into the analysis or repair of these particular Ysus units, please share. The exact Model # of this Ysus is:

EBR77185601

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

I must have misread your second post, I thought you were measuring 205 volts on the VS going to the Y-sus board. Maybe that was with the plug disconnected between the power supply and the Ysus.
Usually one of the first tests is to check the resistance across the VS plug on the Ysus if the VS voltage is being killed.
You will need to check for shorted fets on the board.
Shopjimmy has a repair kit for the Y-sus board

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

No problem, R_J.

There appear to be over 200v coming out of the Zsus (measured that at 222, actually) and then, assumedly, heading over to the Ysus. But, I could never get my digital multimeter's probe deep enough into the connector that enters the Ysus to get an official reading of the voltage coming into the Ysus itself. So, that's when I researched a bit more with a focus on this Ysus and came across the video. I wasn't aware that this simple resistance test could be so revealing. Definitely will remember this in the future. [This test is done with the Ysus connector pulled out in the video, so that's exactly how I performed it as well.]

Yes, I will test for the shorted fets. If I find one or two out, is it okay to replace just those or have you found it best to replace all of them with the help of the repair kit? In other words, are the others likely to go bad anytime soon?

Another question that comes to mind is:
If the upper and lower buffer boards continue to test okay, is it wiser to disconnect those from the Ysus when I first go to test my Ysus repair (or, replacement, if it comes to that) to help ensure the buffers are not damaged. I know that no picture will be produced under those circumstances, but I would be hoping to see the green light come on the Logic/Control board to give some proof at that point that the Logic/Control board is functioning properly. Does that make sense?

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

Here's another video I found where a repair is performed on a Ysus from a LG 60PB6650 but my 60PB6900 uses the exact same board (the EBR77185601):

https://www.youtube.com/watch?v=mZh9Lymglrs

If you have time to review that video, I'd be curious if that matches up with your own personal experience in diagnosing and repairing these LG plasma boards.

[kca]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

R_J ~

Just reviewed how to test MOSFET's accurately and it's clear how to do so if they are taken out of circuit. My question is, is there a reliable way to test these while still in circuit? I took the board off the panel, and ran a bunch of tests with the fets still soldered in. Certain patterns definitely emerged. But, I am not sure if these numbers can be trusted or relied upon.

I can go into more detail about what emerged, but for now just need to know if I have to desolder each of these fets in order to really, successfully test them. Hope there is an easier way.

[R_J]

Re: LG 60PB6900 ~ Relay with cyclical, repeated clicking upon startup

(shorts on the 2 Vs pins were found on this Ysus connector)

You have a short on the Y-sus board, the bad fets will check as a short between drain and source. many of the fets are in parallel so the would need to be removed to isolate the shorted ones. The short may be caused by something else also when you have 20~30 components connected in parallel it can be hard to find the bad one.
If you find a shorted fet, they can usually damage parts connected to their gate circut also. thats why its a good idea to replace the parts in the kit