bad ceramic capacitors on Y-Sustain board of LG50PA6500

[pulper111]

I originally posted this to an older thread but decided to start a new thread since this is for a different TV. I am having a problem with two LG 50 inch plasma TVs (50PA6500) and am hoping someone can help. One is my sisters TV and the other is mine (that I broke while trying to fix hers :-( )

Both have the same power and Y-Sus boards (same part number and numbers on the white stickers). Power boards are fine. However, after some troubleshooting I have found that the Y-Sus boards seem to be the problem. The Y-Sus boards are EAX64282201/EBR73763201. I've tested the resistors using a DMM and replaced one on one of the boards. However, both boards have faulty ceramic capacitors in the exact same locations. I've read that ceramic capacitors rarely go bad, so I'm wondering about this. I have checked them using the MESR-100 ESR Meter and they show up as overflow. The faulty ones are 4 disc shape ceramic capacitors and one blue radial style capacitor.

https://imagebin.ca/v/3XmGxBU7vZIK

https://imagebin.ca/v/3XmHN69v0xJk

Four of the five disc shaped capacitors in the 1st picture are bad, and the blue radial style bad capacitor is nearest to the black heat sink in the 2nd picture. The other two radial style capacitors in the 2nd picture are good.

The symptoms of one TV is that it will turn off 1 second after turning it on. The symptom of the 2nd TV is that it will turn on, there is humming coming from the Y-Sus board, and a faint clicking sound near the top of the board. It will stay on but there is no picture.

Does this sound plausible that this many ceramic capacitors have gone bad? I am new to trying to fix things/troubleshooting so please forgive any errors in terminology that I've used. I have also determined that in one of the TVS the Y buffer lower board is bad too.

Thank you.

[tom66]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

When you say bad...what do you mean?
Shorted is bad. Open circuit (no capacitance) is also bad.
An ESR meter will not read these correctly. It is designed for much larger capacitors, of the electrolytic type.

[pulper111]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

Hi Tom - Thank you for the quick reply! To answer your question, I've linked to two pictures here. The first is using the ESR to test a "good" disc capacitor, and I obtained a reading of 0.084 ohms and the ESR indicates it is a good capacitor so long as it is less than 1000 mf. the 2nd picture is testing a bad disc capacitor (same board and same cap specs). It read "OL" and reads "reading is overflow". I have a few of the disc capacitors that test as being "good" in that the ESR meter indicates that they are good well beyond what their capacitance spec is (for example, these are 0.001mf capacitors and the ESR meter indicates they are "good" so long as they are below 1000mf). I also have 4 disc capacitors that read as bad, meaning that the ESR indicates "OL" and reads "reading is overflow". Hope that clears up what I intended to say. as I indicated in the first post, I am new so terminology is not great yet. Thanks for taking the time to ask for clarification. In addition, just to clarify the pics below, the leads are not touching each other in either of the tests.

https://imagebin.ca/v/3XmtFulymEo2

https://imagebin.ca/v/3XmteGewLcyV

[budm]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

You cannot accurately measure cap capacitance, ESR while they are in circuit dues to fact that the caps are connected to other components in the circuits as well.
"An ESR meter will not read these correctly. It is designed for much larger capacitors, of the electrolytic type." That is correct per Tom66.

[pulper111]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

Thanks to both of you for your help! I took out two disc capacitors from the board (one that measured "good" and one that measured "bad") and they had almost identical readings on my EM.

Can i also conclude the same thing for the blue radial style capacitor (ie that the ESR won't accurately measure that one either when in the circuit)? I know Tom indicated that this the ESR is designed for the electrolytic type of capacitor, but I'm just confirming here.

Thanks again for both of your help!

[tom66]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

The failure mode of these capacitors is not measured on an ESR meter. In any instance, they are unlikely to cause your fault.

ESR meters are only used for large electrolytic capacitors that may have ESR failure. These types of failure are much less common on modern electronics, I cannot recall an LG plasma made in the last five years that has had issues with its electrolytic capacitors.

I would look elsewhere: try measuring all the critical voltages (Vs, Va, Vsc, -Vy and Vzbias) to see what you get.

[maleksa]

Re: bad ceramic capacitors on Y-Sustain board of LG50PA6500

I had a similar problem on my LG 60PA6500, whereby I had a dead Y-Sus Board. Upon power on, there would be a humming noise coming from the Y-Sus Board before the TV shuts down.

Upon checking, I found several bad MOSFETs (under the two large heat sinks), two dead resistors and two dead diodes. After replacing them, I got the TV up and running again.

I did test the electrolytic capacitors and did not find any defective ones.

I would suggest that you remove the mosfets, resistors and diodes for testing. Hope this helps.