TD Systems K55DLT6F Backlights OK but no picture

[dicky96]

Hi guys I got this TD Systems K55DLT6F 55" LED TV here

It has back lights but just a very dark blue screen, no image no menus.

Disconnecting the left hand (looking from the back) TCON cable gives a white screen, or sometimes a blue screen on the same side of the panel as the disconnected TCON and dark on the other side

Disconnecting the right hand TCON cable gives a good picture on the other side of the panel and a white screen that gradually fills out to the edges on the same side as the disconnected TCON - see pics

Ther are test points on the HV77DA TCON board but none are marked with obvious voltage names

Is that anything other than a faulty panel?


Rich

[dicky96]

Re: TD Systems K55DLT6F Backlights OK but no picture

Anybody? IIRC if I disconnect one TCON and the other side gives a good picture, but I have no image at all with both TCON connected then I have a faulty panel?

Thanks
Rich

[vinceroger69]

Re: TD Systems K55DLT6F Backlights OK but no picture

on the lcd panel pcb on the side that shows a white screen have you checked for shorted smd capacitors theres been a couple of threads people have one on the bad side

[dicky96]

Re: TD Systems K55DLT6F Backlights OK but no picture

No shorts across any of the caps on the panel PCB. All the 0 ohm smd 'resistors' read OK too

I also checked from the all the test points on the TCON for shorts to ground. None found.

Richard

[budwich]

Re: TD Systems K55DLT6F Backlights OK but no picture

"normally", as you see when a cable is disconnected from the panel, the panel shows "white". It would appear from the "fringe" on the bad side that panel has an issue along the side and "smear of black" is showing.... it is like a similar effect if you press on an LCD screen. What is the history of the set? Are there tabs bonded along each side?

Related to the above "guess", if power is able to get to the panel but not able to "drain" then the LCD remains powered and shows black... its possible that you may have a bad connection / "improper" smd cap as opposed to shorted one.

[dicky96]

Re: TD Systems K55DLT6F Backlights OK but no picture

Hi Bud
When I remove the cable from the 'good' side it is white all the way to the edges. The bad side is black.

When I remove the cable from the 'bad' side, the good side shows an image, the bad side is white, but as you say with dark fringes to the edges that gradually go white over several seconds. So the white area gradually fills the edges of the screen.

With both cables attached all is black.

The set is less than a year old but the bar who it belongs to lost the paperwork/receipt.

It's used outdoors for the football games but moved in at night.

I didn't look for tab bonds down the sides, I will look in the morning.

My guess is that condensation could be the culprit here. We don't get any rain here (well maybe 3 inches a year and most of that falls in February) but it's common to see condensation covering parked cars in the mornings even though the night time temperature rarely goes much below 20C. I guess we have a very high 'dew point'

[dicky96]

Re: TD Systems K55DLT6F Backlights OK but no picture

@budwich
I can't easily check if there are any tab bonds at sides without dismantling the whole set.

There are no cables going to the sides of the screen that I can see from the mainboard or TCON. There are 6 tab bonds from each of the panel PCBs at the bottom

This is the panel model number (I think) if that helps

[budm]

Re: TD Systems K55DLT6F Backlights OK but no picture

Your LCD panel has integrated T-CON which is part of the tab bonding boards.

[dicky96]

Re: TD Systems K55DLT6F Backlights OK but no picture

Your LCD panel has integrated T-CON which is part of the tab bonding boards.

Hi can you elaborate on what that means please

There is a lvds to the TCON PCB and ribbons connecting to the lcd panel pcbs just like I usually see

cheers
Rich

[budm]

Re: TD Systems K55DLT6F Backlights OK but no picture

Ops, sorry I got your thread mixed up with another thread. Please disregard my comments.

[Andrew F. Ali]

Re: TD Systems K55DLT6F Backlights OK but no picture

The flat cable from the T-Con Bd. to the Source Bd--are they in good condition? Do they have any abnormal marks on them? Did you try switching left and right flat cables to see if the problem remains on the originally bad side?