Sharp LC50LE752E no picture and backlight, indicator light is lit

[roy.zhero]

I acquired a free 50” TV. IT is a Sharp LC50LE752E. It does not show a picture and has no backlight, although the indicator light turns blue meaning it has turned on.

When power is plugged in, the indicator light will turn on blue, the backlight stays off and nothing is visible, even with a flashlight. When pressing the touch buttons on the tv nothing happens. When pressing buttons on the remote control the indicator light will blink indicating the IRsignal was received, but nothing happens.

When I hold the force-on-combination it will turn on. It then shows a perfect screen without glitches. After powering it off with the remote the indicator light turns red. I can power it on again via remote. But after 10 minutes of inactivity I noticed the screen had turned off again while the indicator light was still blue.

Troubleshooting:

Measured power supply pins:

Power supply connector going to main board:
1 (N.C.): 0
2 (ERR): 0
3 (PWM): 3.64
4 (BL_ON): 0
5 (PS_ON): 3.285
6 (GND): 0
7 (GND): 0
8 (5.75V): 5.88
9 (5.75V): 5.88
10 (GND): 0
11 (GND): 0
12 (12V): 11.97
13 (18V): 17.79
14 (5Vs): 5.18

Backlight connector going to backlight board:
1 (24V): 23.98
2 (24V): 23.98
3 (24V): 23.98
4 (24V): 23.98
5 (24V): 23.98
6 (GND): 0
7 (GND): 0
8 (GND): 0
9 (GND): 0
10 (GND): 0
11 (ERR): 0
12 (BLON): 0
13 (N.C.): 0
14 (PWM): 3.64

There is no backlight_on voltage. There is never any voltage on ERR during boot.
Manually shorting the Backlight on with the Power supply on lights the backlight normally and will stay on as long as I short it. All sides will light up.
I have reseated all connectors going between the boards.
I noticed pressing the touchbuttons on the TV does not work, nothing happens. Even when I forced it on it did not respond however the remote works normally when the TV is forced on.

The main board is DUNTKG135FM08.
The power supply board is RDENCA459WJQZ.

Board diagrams in PDF:
https://1drv.ms/b/s!AkpE6xgs6VHNhGNwakvV
I have uploaded photos of the main board and the power supply board.

I am guessing there is a problem with the main chip or the standby chip IC3800. I'm not sure where to go from here. Any help is appreciated.

[roy.zhero]

Re: Sharp LC50LE752E no picture and backlight, indicator light is lit

Working link to board diagrams:
https://1drv.ms/b/s!AkpE6xgs6VHNhGPi...rNn3R?e=O5Mh3S

[Diah]

Re: Sharp LC50LE752E no picture and backlight, indicator light is lit

glitch at SPI Flash.. try freez or heat the spi flash if the set start to turn on.. then need to dump it and write it on new spi

[roy.zhero]

Re: Sharp LC50LE752E no picture and backlight, indicator light is lit

Thank you for your reply Diah.
Due to travel I have only been able to test it yesterday.

I identified 3 memory chips (IC3501, IC3502, IC3503) and used freeze spray on all of them and tried to turn the TV on (1st attempt). Unfortunately no change. Tried the freeze spray on the standby chip as well (IC3800)(2nd attempt) as well as the complete region of that side of the main board (3rd attempt). No change in any of the attempts.

What other things could the culprit be?

[nomoresonys]

Re: Sharp LC50LE752E no picture and backlight, indicator light is lit

Sometimes you have to freeze the crap out of them to get results.