https://hisense.encompass.com/model/HIS7...

IMAGE: No image, but all else seems to work.

BACKLIGHT: I can see many of the LEDS from behind when powered with back removed. I can also get the general "full screen glow" from the front when powered. And the "full screen glow" changes intensity as I click through menus....so sure seems to be working.

AUDIO/MAINBOARD: both seem to be working fine. I can select a remote shortcut for Netflex and even start blindly playing content and hear the menu clicks and content, for example.

POWER: No bulging caps or obvious damage.

TCONN: I was so supremely confident it was the Tconn board based on the symptoms that I just ordered one and put it in. Then shocked/disappointed to see the problem remained.

One, small clue. About 8 months ago this same issue was happening.....and the fix for a while was to leave the TV powered for about 60 seconds, then turn it off and immediately back on again. This always restored video to operation, but I suspected the Tconn and ordered it. But then I never replaced the Tconn because for about another 6 months it just worked on the first try every time. Until last week, all of a sudden the symptoms returned and the warmup/power-cycle trick also failed me. So I put in the TCONN fully expecting the issue to resolve....but nope. Still no image output.

Not sure where to go from here. I can blindly try to replace the power or mainboard. I've very disappointed in Hisense as I called them when the problem first started occurring but I was just a few months past 12 month warranty. TVs should last longer than that....

PS: I'm an EE with some amount of tools and skills, but contrary to family beliefs that doesn't necessarily translate to a master of modern home electronics repair.

Boards Layout:

Power:

Backlight Driver

Tcon:

The below conneted /covered. The board above is the one just removed/replaced.

Main:

Other items of note:

• I have removed, reseated all connectors and wiggled them a bit during operation to look for anything faulty.
• I checked all power with a multimeter with the labeled voltages. Everything was correct with the exception of the indicated 13V to the backlight which very strangely reads near 29volts. The backlight board doesn't label a voltage input...just shows VIN. Still, the backlight and the local diming feature seem to be working (if I disconnect power to the backlight, the obvious difference of no backlight. if I disconnect the connection from backlight to mainboard, I get backlight but the backlight doesn't change on the screen as I click through menus I can't see...which I belive is the local dimming at work)
• The main board takes 12V which is measured/correct. Again, I have audio and can hear it boot and navigate menus, so the main board seem to be largely working...even the local dimming control. Best I still get no image output.....even after replacing the Tconn.
• At this point, all I can think of is changing out the mainboard....but I'm not sure I want to fork over the $300 clams and risk it not working.

⟐ Answered January 26, 2024 at 21:42 MST