JVC EM55FTR No Picture, Yes Sound, Yes Backlight

[TheTesterMan]

Samsung UN55H6203AF
TV has no picture but is back light and has sound.

Boards
T-Con HV55WU2- 370
Main 3655-0822-0395(3B)

Measurements
All measured Main board test points check out.
All measured T-Con board test points check out ONLY when left panel ribbon cable is disconnected. If the cable is connected, most of the voltages around the ribbon cable/lower right/left IC drop to 0v ( as if something is shorting )
Cannot find any shorts to ground anywhere on T-Con and on left side Panel PCB

Observations
When the left side panel ribbon cable is disconnected and TV is powered, a picture can be seen on the right side of the TV while the left is completely white. When the ribbon cable is connected, then the entire panel is black ( with backlight)
Replacing the T-Con board did not resolve the issue.

Questions
At this point I am confident that this is a bad panel but wouldn't there be some sort of evidence such as a short ? I measured all the components on the panel PCB and they all seem ok, nor was I able to find any shorts.

Before I rip this TV apart for parts thought I first check in with you guys for any suggestions/

[nomoresonys]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

Test connector from mainboard to powerboard on powerboard side with all boards hooked up, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description/name and condition both off and when you hit power on.

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

Power Board Connector OFF, ON
Dim 1 -> 0, 2.7v
Dim 3 -> 0, 2.7v
BL_ON -> 0, 3.32v
PS_ON -> 0, 3.31v
GND -> 0, 0
GND -> 0, 0
19V -> 19.08, 19.08
19V -> 19.08, 19.08
19V -> 19.08, 19.08

LED OFF, ON
D1+ -> 0, 112v
D2+ -> 0, 111.7v

FYI - I have at my disposal not only a multimeter but also a scope should there be useful measurements I can take.

[budm]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

There is nothing wrong with the power supply because you are getting sound, backlights, and half of the screen if one of the cable (good side) between panel and T-CON is not connected.
You have problem in the LCD panel based on your description in post #1.
So you check the resistance of all the caps on the tab bonding of the bad side of the panel? You are 100% sure?

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

@ budm I agree with your conclusion based on my findings but was willing to recheck anything before giving up.

Yes, I went back and did the following:

Resistance check and continuity between all pcb components to ground. OK

Checked all caps for short. OK

Checked resistors and jumpers. Ok although not sure which are jumpers

With Left side connector connected to Tcon, checked Resistance on all Tcon side pins to ground. When one was found ( I think about 6 ), I quickly disconnected the ribbon to see if the short came from the PCB panel side. OK

No matter what I do I cannot find a short, but clearly something is pulling most of the Tcon down when that left side connector is connected.

[budm]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

What is the actual resistance you are seeing?
Can we see the pictures of the tab bonding boards that the LCD panel is connected to?

[neilc6]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

https://www.badcaps.net/forum/showthread.php?t=50646

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

@ budm, if you could specify which measurement you are referring to I can post results.

@neilc6 thanks for the link, that sent me down couple of hours of research some of which I have applied without results. I have not yet cut any ribbons, but have tried taping various pins, usually a few at a time, from one side to the other and never got a picture.

Lastly, this TV does have side tabs, I tried taking pictures of those but was difficult. Suffice it to say that none of the ICs on the side panel ribbons look burned or unusual.

[Duranitron]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

did the owner told you what happened to the TV before this happens? lightning strike perhaps? or the tv is dropped. this clearly leads to a bad panel try to switch the two cables connected to the lcd and tcon hoping the cable is bad . something is shorting out in the lcd panel pcb board focus on that! hope this helps..

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

did the owner told you what happened to the TV before this happens? lightning strike perhaps? or the tv is dropped. this clearly leads to a bad panel try to switch the two cables connected to the lcd and tcon hoping the cable is bad . something is shorting out in the lcd panel pcb board focus on that! hope this helps..

Yes, she said it simply stopped working. She is a very old lady living alone so I know nothing was thrown at it, but you never know.

Yes I agree there is something in the panel, and or panel assembly, putting the Tcon in standby power (this is known because both sides of the Tcon partly shut down).

Yes, I have tried both new Tcon and swapping cable.

[budm]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

https://www.badcaps.net/forum/attach...5&d=1564526438
There are a bunch of MLCC (light brown body) caps that you need to check them all for the DC resistance to find out if any one of them show low resistance reading or not.

[nomoresonys]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

Sure seems like the problem is after the tcon, what's left but the driver board?? Probably isn't the issue but did you try cleaning the tcon ribbon cables?

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

https://www.badcaps.net/forum/attach...5&d=1564526438
There are a bunch of MLCC (light brown body) caps that you need to check them all for the DC resistance to find out if any one of them show low resistance reading or not.

I checked these already and none seemed to be an issue but will test again and post results. Gonna try to borrow a cap tester also to fully verify.

@nomoresonys, yes I tried cleaning all the cables and connectors are best as possible, but clearly this problem is not intermittent, its a hard short. The only thing that stops it is removing the left side cable. I tried to mask many pins and still want not able to narrow it down to a few select pins.

[nomoresonys]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

Guess that ribbon cable could be faulty???

[budm]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

I checked these already and none seemed to be an issue but will test again and post results. Gonna try to borrow a cap tester also to fully verify.

@nomoresonys, yes I tried cleaning all the cables and connectors are best as possible, but clearly this problem is not intermittent, its a hard short. The only thing that stops it is removing the left side cable. I tried to mask many pins and still want not able to narrow it down to a few select pins.

So what are the lowest DC resistance did you get?

[Andrew F. Ali]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

These MLCC should read open or infinity. If you get any kind of resistance reading post what you got as budm asks.

[budm]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

I already ask in my post #6:

What is the actual resistance you are seeing?
Can we see the pictures of the tab bonding boards that the LCD panel is connected to?

But never show the result, here we are at 15 posts, no readings shown.

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

I measured all the caps on both panel strips ( bad left and good right ).
Half the caps read roughly 300k while the rest read 1meg, this is the same on both sides.
I also checked the caps with a cap meter ( on a fluke multimeter, not very accurate ) and all the caps measured roughly 6microF.
All this with the ribbon connectors disconnected.

[Duranitron]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

something in the lcd driver board is shorting when powered. visual check it for burned parts, try to find overheating parts, try the voltage test. do you have schematics of the lcd driver board? or try to poke the lcd ribbon cable, maybe fault in the ribbon cable specially when its hot so try to touch it maybe a loose or shorted connection and if that's the case it requires lcd bonding machine better yet buy the old lady a second hand TV hehehe just joking dont give up you can do it patience is a virtue my friend. just keep on trying.....pls. post your progress thanks.

[TheTesterMan]

Re: JVC EM55FTR No Picture, Yes Sound, Yes Backlight

something in the lcd driver board is shorting when powered. visual check it for burned parts, try to find overheating parts, try the voltage test. do you have schematics of the lcd driver board? or try to poke the lcd ribbon cable, maybe fault in the ribbon cable specially when its hot so try to touch it maybe a loose or shorted connection and if that's the case it requires lcd bonding machine better yet buy the old lady a second hand TV hehehe just joking dont give up you can do it patience is a virtue my friend. just keep on trying.....pls. post your progress thanks.

I appreciate the vote of confidence and do not plan on giving up.. the issue really is time, going through a tough time right now which doesn't leave me much time for this and why I did not always respond immediately to some of the requests on this forum. I plan to get back on this next week and provide measurements/results.