The 7.5vDC for the 13V STBY may be normal in standby mode, since there is no separated standby power supply so they may keep the Voltage low just enough to run the main board, and when PS-ON is present and then the PFC Booster circuit kicks in then the 13V and the 80 will be normal.
That is why I ask OP to see what DC V he has on the main filter cap since the PS-ON is present.
This would explain a lot of half voltage readings we have been seeing here on lots of posts.
Since you indicate that the Backlights did flash on for seconds, then you should unplug the TV and put black probe on the chassis, keep red probe on the 80V pin then plug the TV in and watch to meter to see if it jumps up to 80V or not, repeat the same test on the DRV_ON pin.
BTW, since you do have PS-ON, what DC Voltage do you have between the two legs of the main filter caps?
390v
Since you indicate that the Backlights did flash on for seconds, then you should unplug the TV and put black probe on the chassis, keep red probe on the 80V pin then plug the TV in and watch to meter to see if it jumps up to 80V or not, repeat the same test on the DRV_ON pin.
An 80v pin on the DRIVER board does jump to 80V and then drops to 55V...
The DRV ON pin "jumps" to 50mV, then goes haywire but never above 1V and then holds steady at .9V
BTW, does this TV has WiFi since it is smart TV?
If it does, what happen if you disconnect it?
You have main board problem at this point, you should be able to turn off the TV if the power control function of the main board is good.
Usually if there is error signal such as bad T-CON, Backlights circuits, etc, the main board will be forced off, yours is stuck on.
You have main board problem at this point, you should be able to turn off the TV if the power control function of the main board is good.
Usually if there is error signal such as bad T-CON, Backlights circuits, etc, the main board will be forced off, yours is stuck on.
Yea, I'm beginning to think it's a Main board problem too..
I could have swore I checked and saw it had a latent image.. But I get one of the backlights on using my LED Power thingy and power up the TV and get no image at all...
That seems to seal the idea that it's a main board issue...
Hooked it up and powered up the TV.... Same problem.. LEDs flashed for a second and then went off... :^(
Something weird happened though... In the brief moment where the LEDs were on, half the display panel was white and the other half, I *thought* I saw the regular LG start up graphic...
The white part of the panel indicated to me that the TCON board connector was not inserted properly..
Powered everything down and inserted the TCON connector properly..
Still have the momentary flash of the LEDs, but now there is nothing on the display panel.. Not even a latent display..
So, now things are exactly as before.... Nothing on the display panel, not even latent'ly... And only a momentary flash of the LEDs... And, I should note, the TV cannot be turned off...
As much as I hate to do it, I am thinking I am going to have to crack open the display panel and check the individual LED strips..
OK, I am confused, in post #1 indicated the Display is fine just no backlights,so what happen if you put old main board back in?
Yea, I might have been mistaken about that initially...
Subsequently (a few days ago) I used my LED Power Supply to turn on a segment of the LED Array and then powered up the TV but I never got anything on the display...
So, either I just assumed that I got a display image based on my assumption it was an LED strip issue (possible)... Or I actually did have a latent image initially and my subsequent tinkering frak'ed that up (equally possible)...
I am leaning more towards I made a wrong assumption....
If I got a latent image, then a bad LED strip would make sense..
But not getting a latent image makes me lean towards a bad MAIN board.. Or, should I say ANOTHER bad MAIN board.. Which is possible, I spose...
Is there a way to jumper or short some connections on the Driver/Power board to force the LEDs on?? Leaving the MAIN board totally taken out of the loop???
In an effort to confirm once and for all that the LEDs are not the problem, I hit on the idea of taking each pair of wires off of the DRIVER connector and place them on the DRIVER board one pair at a time..
Each pair gave me the same thing.. An LED strip/area came on then flashed off... So, that told me that the LED array is NOT the problem..
After I had tested the last pair, I put them back into the connector and then plugged the connector back into the DRIVER board...
Powered up the TV and, I'll be at some beach, the LEDs came on and stayed on!!!!
I thought to myself, I said, "Self!? Well, ya fixed the LED issue, but you still don't have an display.."
And, some beach again, I sure had a display!!!???
Apparently, it's all linked together.. You can't have a display if the LEDs aren't coming on and staying on...
So, not one to look a gift horse in the mouth, I am gonna count this one as a win!!
Do you think it is the mainboard or the driver board. I am getting the same issue. Can you get any sound .
I don't think your problem and my problem are the same..
One way to confirm that is to take a powerful flash light and shine it into the screen at an angle...
Turn the TV on.. If you see a latent image, then your problem is likely a bad LED strip... Those are a major bear to change, but is doable if yer careful..
If you don't see a latent image, then the problem is likely one of the boards. Most likely the Main Video Board..
If it IS a Main Board issue and if I can confirm that my old Main Board is good, I'll be happy to sell you the replacement board I got (which I know works fine) at the cost I paid for it...
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