TCL 43S431 Backlight issue or Power Supply

[handsworth]

I was wondering if anyone else has come across this problem. What was the problem?, and was it solved. I recently picked up 2 of these tvs and both initially diagnosed as bad backlights. When turned on, the backlights flash the red logo screen. Sound and an image is clear using a flashlight. So I buy 2 sets of leds. When they arrive I take one tv apart and test the leds before removing them. OMG they all work. but I put the new ones in anyway. So I think its the power supply. I swap PS from one to the other and same results. Now here is the issue and really confused me. I reset the tv using the reset button on the main board. Tv went into recovery mode. Backlights are on and stay on while I go through all the steps. Tvs says updating and I think its done. Tv restarts, I get picture, sound and backlights like normal, then backlights shut down. I'm back to original issue. Need help or explanation of whats happening. TIA

[vinceroger69]

which mainboard is used in this set i wonder if its turning the backlight signal/voltage off

[handsworth]

The PS is the same but the MB are different. As of now, both tvs are at initial setup like right out the box. No backlights but both tvs have sound and image.

[tech9pc]

I have same problen with one like you ... don't think it is your power supply or your leds either. I picked up a free TCL 43S446 get standby light and works without backlights turning on ... but no power to leds. Ordered another power supply and was garbage didn't even get any standby light .. so put original back in. Than went and ordered a LED replacement strip .. same thing as original .. and still no backlight on power tv on. At this point It has be something like bad circuit on the panel. I have not went back to it yet. I think all these models are suffering from the same flaw.

Power Supply: 08-L12CLJ1-PW200AA

Know Models:
43S434
43S435
43S433
43S446
43S431

IPS Panel: T430QVN03.M

Main Board: TCL 30800-000328 - 40-R51MTA-MAA2HG; 11602-500227

No T-Con Board

[Diah]

you can slide out the BL_ON wire from the power boards socket... and jumper the pins of it in the socket via 1KR to Power_on pins... when the BL come on keep this DIY. because yours MB didn't sent this signal anomaly

[tech9pc]

Hi Diah thanks for all your input. Do you mean the Red wire is BL_ON? and jumper it to where? with a 1KR? is that a 1 K Ohm Resistor? .. sorry dumb here lol ... just an amateur. Appreciate your expertise.

[EazyBone]

Also test these and see if there is continuity on any, and test resistance if there isn't. There shouldn't be.. but let's see. I fixed one recently with this issue. Not exactly the same so test this while doing diahs suggestions.

[Diah]

Hi Diah thanks for all your input. Do you mean the Red wire is BL_ON? and jumper it to where? with a 1KR? is that a 1 K Ohm Resistor? .. sorry dumb here lol ... just an amateur. Appreciate your expertise.

NO..
the red socket which it go to Mainboards .. here are the BL_ON and power _ON... search on yours Power boards you will find Print Chart describe this socket wiring by Number and name , if the chart not on top look at the downside of the boards...
you should 100% sure of the Pins location., other wise you could damage the PSU

[tech9pc]

OK I see what you mean now .. looked at the board pins like you said Diah. Thanks for the tips and suggestions all. I will try this when I get a chance. I will have to research it a bit before I attempt it .. skills are not very good lol.

[handsworth]

So I tried to get the backlights to turn on by jumping the 2 pins with a 1kR. The P_ON and the Bl_ON pins are charted on the back of the Mb. When turned on, the logo screen appears for 15 seconds (I timed it) and then the backlights go out. No backlights but sound and image still present. I also think the problem is with the main board not sending the signal after initial startup. There are a few MB on Ebay for less than $25, so I'll try one.

[vinceroger69]

So I tried to get the backlights to turn on by jumping the 2 pins with a 1kR. The P_ON and the Bl_ON pins are charted on the back of the Mb. When turned on, the logo screen appears for 15 seconds (I timed it) and then the backlights go out. No backlights but sound and image still present. I also think the problem is with the main board not sending the signal after initial startup. There are a few MB on Ebay for less than $25, so I'll try one.

did you reemove the BL_ON wire from the power board socket before jumping the two pins together

[handsworth]

yes I did

[Diah]

yes I did

some things wrong you did... maybe you jumber other one.. no reason to stay on 15 seconds unless the LED defect
show us the print chart of the socket on power boards

also with reference TV Chassis measure the red wire of LED+ at time you plug the tv in wall... mark the high and low V you will have

[handsworth]

It was the power supply. I bought a repair kit from ShopJimmy ( $38) which included the main board, PSU and T con. 1st tv fired right up and stayed on. I put the original MB back in and tv turned on and everything is ok. I repeated this on the 2nd tv and the results were the same. Unfortunately, the second screen had a vertical line down the right side. So out of 2 free tvs, I got one to work for 38 bucks.