Insignia FireTV NS-50DF81NA19 backlight on but no image

[jason123]

Hello,
Hoping for some help as i am perplexed by this one. Backlight comes on fine, unit is responsive to remote, and all indications are good. VM and VA rails coming from power supply are around 16 V. Green LED on the TCON comes on.
2 ribbon cables from TCON 2 panel act normally i think. Disconecting the left one results in right hand side of the screen white. Disconnecting the right ribbon, has no effect (full dark screen)

So.. thought it's TCON...got one but TV acts the same (just backlight and no picture.) So i got a main board, and the TV still acts the same. What the heck. Could be bad panel? Visual inspection shows nothing burnt or odd.

Any thoughts? Tried disconnecting the wifi / bluetooth module. No effect. Help!

[CapLeaker]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

Those two ribbons on the tcon go to another board each. My bet is the board on the side that stays black.

[jason123]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

Do you mean the panel tab boards? I usually see burn mark or some indication of failure. These panel tabs look pristine. And i would think if one side is bad the other side would show an image? I cleaned the ribbon pins with alcohol and no change

[nomoresonys]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

maybe try the "tape cut-off' method.

[CapLeaker]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

Do you mean the panel tab boards? I usually see burn mark or some indication of failure. These panel tabs look pristine. And i would think if one side is bad the other side would show an image? I cleaned the ribbon pins with alcohol and no change

Only because it looks good, it doesn't mean it is good. It doesn't have the right symptoms for bad tab bonds. But symptoms also do fit for those little small boards to be the problem. There should be test points called like VGL etc check them and compare them.
Also only on the assumption to swap a new board in, also doesn't mean you got a working board. That has been proven here many times.
Nomoresonys mentioned the tape cutoff method. That would be my last resort. Get some help if you do this, to make sure to cut off the right one.

For starters, I'd put a TV show or something on one of the inputs and probe the LVDS with an oscilloscope. If you see small changes as the picture changes, the main board is good. Then your off to the tcon checking for voltages, panel Power etc.

[jason123]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

Only because it looks good, it doesn't mean it is good.

I get you.. just typically, if there is a problem on these tabs, there is burn marks or other visible issue.

It doesn't have the right symptoms for bad tab bonds. But symptoms also do fit for those little small boards to be the problem. There should be test points called like VGL etc check them and compare them

Not much is labeled on these boards. I went around the cpas (bypass I presume) and some have 3.2 V, others don't have any voltage on them. Many measured short (which I wouldn't expect on these capacitors) and there are so many - took a chance and removed a few to see if I can get lucky, but I wasn't ... there are still many with 0 Ohm across.

Also only on the assumption to swap a new board in, also doesn't mean you got a working board. That has been proven here many times.

Agree - I just wouldn't have expected the exact same symptoms from 2 main boards and 2 TCON boards. But, I could very well have received bad boards.

Nomoresonys mentioned the tape cutoff method. That would be my last resort. Get some help if you do this, to make sure to cut off the right one.

For starters, I'd put a TV show or something on one of the inputs and probe the LVDS with an oscilloscope. If you see small changes as the picture changes, the main board is good. Then your off to the tcon checking for voltages, panel Power etc.

I have activity on every pin almost of the LVDS - very ugly captures with a scope but I don't have the right probes anyway for this measurement.

I'm giving up I think on this one.. I think the panel is bad and I can't seem to find easily a bad part or section on the tabs.

Thanks for the help

[neilc6]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

With panel boards, shorted chip caps will be a likely suspect if a new tcon didn't fix it. There is a youtube video of a guy isolating the short with a milliohmmeter. https://www.badcaps.net/forum/showthread.php?t=105788

Tape cutoff typically works if you can get one side to show a good screen since you are blocking signals to the bad side with the good side compensating.

[nomoresonys]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

I have used the tape cut-off successfully on more than one totally dead set, meaning no signs of life at plug in or turn on. Just got 15 clunkers in today, I expect it will prolly work on at least 5 of them.

[CapLeaker]

Re: Insignia FireTV NS-50DF81NA19 backlight on but no image

As long as you can see differences with the oscilloscope in the lvds when the pictures changes your main board is working.