Samsung plasma PN64F8500 Y-sustain board

[aG738]

Guys, I need your advise to troubleshoot the Ysus board on Samsung PN64F8500. The symptoms are as follows:

When switching the TV on via remote, no video, blinking LED for about 1 min. Then sound is on, all remote controls are fully functional, but still no video. If I am lucky, it works from the 2nd switch on depending on the room temperature.

First, I was thinking that it was the power board, bad capacitors. I have checked all electrolytic capacitors, measured ESR (I use Atlas ESR70), but could not find any faulty ones.

One more thing. It looks as the ambient temperature affects it a lot. It works perfectly fine when it is below 22 °C, switches on from the 2nd try under 22 °C – 24 °C, and almost impossible to switch over 25 °C.

According to many threads, having sound and no video means problems with the Ysus board. So, I have checked all electrolytic capacitors on the Ysus board and again could not find any bad ones. Still I replaced most of electrolytic caps, but it didn't help. Then I found this thread on avsforum - people had a very similar problem with the PN64F8500, which was fixed by replacing 106 MLCC caps on the Ysus board. I removed the suspected 106 caps, a few of them measure only 8uf, which is just below the tolerance level.

I can only measure capacitance over 1uf with the Atlas and am not sure if I want to buy a decent LCR meter to measure all MLCC.

What shall I do next? I am thinking to replace all 106 caps, but maybe it makes sense to replace all ceramic caps on the Ysus board because the TV is 6 years old?

Since the TV is very sensitive to the ambient temperature and can be switched on only below 22 °C, should it be only because of a faulty ceramic cap?

Any suggestions? Just replace all caps blindly or narrow bad ceramic caps down somehow without LCR?

Thanks!

[jjanssen7]

Re: Samsung plasma PN64F8500 Y-sustain board

https://www.badcaps.net/forum/showth...ight=PN64F8500

[aG738]

Re: Samsung plasma PN64F8500 Y-sustain board

https://www.badcaps.net/forum/showth...ight=PN64F8500

Thanks! I have replaced all 106 (10uf) capacitors on the Y-sus and everything works perfectly fine. Still I cannot figure out what was wrong with the old caps as they all measure within the 20% tolerance band. Probably, I need to test them under different frequencies and different voltages to find out what exactly the problem was.

[jjanssen7]

Re: Samsung plasma PN64F8500 Y-sustain board

In my experience 20% makes a difference with this YSUS. That's your answer right there. Given your testing might add 5% difference, your caps could be 25% off their specs.