Seems mostly likely buffer board, COF, or the panel.

Check for shorts on caps (multimeter in diode mode on both end of cap) on the bad 1/2 buffer board. If have shorts will need to do voltage injection method to find what gets hot first.

More Update

Not fixed (and maybe not possible) but posting more info on this TV's design.

Traditional T-Con to each buffer board disconnect test doesn't work

The T-Con on this TV is actually on the left (looking from rear) buffer board. So the only hope to easily test which buffer board failed is if the right buffer board (without the T-Con) failed and find failed signal through masking the flex traces. Unfortunately likely not true in this case where the left buffer board containing T-Con failed.

The row gate signals are generated by T-con on...

Yep, lead free is brittle with thermal cycling and inertial vibration and leaded is soft and handles it much better.

Lead free messed up soldering in hot environments from 2000+ to mid 2010s. I've seen it on car ECU and TCM (Transmission Control Module often mounted on the hot transmission), laptop GPUs, and of course these Vizios. Problems with these ~2015 vizios are 1) runs hotter with first introduction to more functions (smart tv) and resolution (4k) without any forced air cooling. 2) TVs gets older less power efficient chip fab processes compared to phones/computers....

hot air station with square nozzle + side added flux definitely helps. Usually a bottom heater is also necessary to prevent board warpage to avoid damage as well as planer for all the BGA balls to contact. But any oxidized cracked BGA solder balls will still be there embedded in the reflowed balls ready to crack again eventually ...

Describe your reflow process. I've not seen any non professional process (pro = SOC removal, reball, resolder with reflow station) last and depending on method, temperature, and duration, its possible not even all the SOC balls have been reconnected. I have used toaster oven to bake several of these boards and achieve complete revival but failed not too long after.

The reason rebaking reflows don't work is because once SOC solder balls crack, the cracked surface gets oxidized. Rebake just reconnect around the oxidization poorly but eventually fails again. I posted a few years ago...

Mine (TCL 55S425) has similar failure. One failure was TVS which got picture working pretty good other than some horizontal lines. Further tinkering probably caused more COF failure.

https://www.badcaps.net/forum/troubl...l-buffer-board

On a different TCL 55" model (55S405), I found 2 differnet panel+T-Con manufacturer despite same TV model. You might check your T-Con in case 43" had multiple panel...

Finally did more diagnostics. I think unfortunately found short in COF on the bad buffer board.

• Failure picture in the immediate previous post (badcaps no longer display post # for me when signed in)
• Identical transistor circuit in middle of both good and bad side buffer board. Shows differences when measuring voltage (powered on) and resistance (powered off and buffer board disconnected to T-Con)
• Bad side shows a short. Removed transistor Q001 to do short finding voltage injection (if not removed, current will flow through Q001)
• 2 hot spots shows with voltage injection at R006 ( markings

...

If Replacement board is used, maybe it also failed? Very common on these Vizio main.

You could check the inductors on main to see how many voltage rails the main board produces. Negative to board ground. Positive probe inductors (larger silver rectangular components) But this requires removing the heatsink which is quite difficult on these Vizio main boards. I think all the rails to run a processor (~1 for processor, ~1.8/2.5 for RAM, 3.3 for flash memory) all come on without needing code to run....