Sharp 60LE630M DPS-165HP-2A: No Backlight

[beetle1303]

I have a Sharp model LC-60LE630M that has no backlight.

When connected to wall socked and switched on, the red standby light is on. Pressed the power button, the green light is on for ~10sec then start flashing red light 1 time slowly.
There is no picture, no sound, and no light. But with a torch light, can still see the no-signal fizzle pattern.
I have tried the "forced on" combinations like pressed and hold Vol+ and ChnDown, and Input and Vol- buttons , no effect..

I disassembled the TV to check on the led strips. There are 4 strips of 60 leds each, 2 each at top and bottom edges. Using DMM in Diode mode, each led is tested good showing 2.5V on DMM. There are 1-3 bad leds on each of the strip, which I removed but shorted the path since I have no replacement leds. Reason for shorting it is because the leds are in series within the strip, and a open led will rendered all the leds behind it not light up..

Reassembled and re-tested - still the same.

I have then check the voltages of the power board, DPS-165Hp-2A:
PD Connector Pins Stand-by Powered On
PD1 – PNL12V 0.01V 11.87V
PD2 – PNL12V 0.01V 11.87V
PD3 – GND 0.01V 0.00V
PD4 – GND 0.01V 0.01V
PD5 – UR13.2V 0.01V 12.88V
PD6 - UR13.2V 0.01V 12.86V
PD7 – UR13.2V 0.01V 12.88V
PD8 – UR13.2V 0.01V 12.86V
PD9 – GND 0.01V 0.00V
PD10 – GND 0.01V 0.01V
PD11 – GND 0.01V 0.01V
PD12 – GND 0.01V 0.01V
PD13 – AC_DET 3.10V* 3.10V
PD14 – PS_ON 0.00V 3.63V
PD15 – BU5V 5.05V 5.05V
PD16 – PNL_POW 0.00V 3.18V
PD17 – N/C 0.50V** 0.98V**
PD18 - N/C 0.01V 1.68V**
PD19 – DIMMER 0.01V 0.01V
PD20 – N/C 0.01V 1.42V**
PD21 – OFL 0.00V 0.00V
PD22 – ERROR 0.13V 0.03V
PD23 – N/C 0.40V** 1.13V*
PD24 – STB 0.01V 0.00V

*voltage dropped to 0V in few seconds
** voltage dropping very slowly

And with black probe on chassis, red probe on each of LED1+, LED1- to LED4+ and LED4-, all showing 0 volt. The 2 big capacitors around them read 208Vdc.

And disconnecting the LED connector, the reading on the PD pins remain unchanged.

Kindly help to point of if anything obviously wrong or bad, or need further investigation.

Thank you.

[beetle1303]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

I have since read more postings on this forum, and did some experiments.
I read about led strips shorting to chassis, and sure enough one of the 4 was shorted to chassis. I fixed it and some of the weird diminishing voltage on some of the pins are gone.
Here are the readings:
PD Connector Pins Stand-by Powered On
PD1 – PNL12V 0.01V 11.87V (no change)
PD2 – PNL12V 0.01V 11.87V (no change)
PD3 – GND 0.01V 0.00V (no change)
PD4 – GND 0.01V 0.01V (no change)
PD5 – UR13.2V 0.01V 12.88V (no change)
PD6 - UR13.2V 0.01V 12.86V (no change)
PD7 – UR13.2V 0.01V 12.88V (no change)
PD8 – UR13.2V 0.01V 12.86V (no change)
PD9 – GND 0.01V 0.00V (no change)
PD10 – GND 0.01V 0.01V (no change)
PD11 – GND 0.01V 0.01V (no change)
PD12 – GND 0.01V 0.01V (no change)
PD13 – AC_DET 0.00V 3.10V (new)
PD14 – PS_ON 0.00V 3.63V (no change)
PD15 – BU5V 5.05V 5.05V (no change)
PD16 – PNL_POW 0.00V 3.18V (no change)
PD17 – N/C 0.14V 0.25V (new)
PD18 - N/C 0.01V 0.13V (new)
PD19 – DIMMER 0.01V 0.01V (no change)
PD20 – N/C 0.01V 0.12V (new)
PD21 – OFL 0.00V 0.00V (no change)
PD22 – ERROR 0.13V 0.03V (no change)
PD23 – N/C 0.03V 0.50V (new)
PD24 – STB 0.01V 0.00V (no change)

But still no backlight..

I tried shorted Pin16 to Pin24 to force a 3.63V when power on, no effect.
I then changed to short Pin15 to Pin24 to force a 5.05V on standby and power on, also no effect.

Bottom line, still no backlight..

[gavric]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

If you just remove and not replace leds your final result and picture will be bad. You will have bad missing lighting and it will glow weird and it will look like crap.

[beetle1303]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

Yes, I would expect uneven brightness and primary objective is determine if this error code caused by bad led strips can be reset after the led strips are "repaired".
I have since bought a led tester, and all 4 strips tested working (with a few leds on each strip bypassed).
But I simply do not see the led strips being triggered during power on sequence.... I removed the screen and all the layers of reflectors and diffusor, etc, and cannot see even a short flash of light..

Unless this due of each led strip has some leds bypassed, not being fully lit and the resistance is therefore lowered?

[beetle1303]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

Update:
I have since gotten another Sharp 60LE631M tv with a small section of lcd screen faulty due to COF issue, but otherwise a fully functional TV.
I took out the logic board from the backlight problem TV to test on this new TV and it shows exactly the same symptom - flashing red led light.

I did not try the good main board on the no backlight TV because of partially working led strips. So i instead salvaged the LCD screen and the tcon board, and installed them onto the partial screen faulty TV, and gotten a fully finchtional TV out of these 2 TVs.

This post is considered closed.
Thank you.

[R_J]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

Unless this due of each led strip has some leds bypassed, not being fully lit and the resistance is therefore lowered?

This will not work, the backlight driver will detect the wrong current and shut down.
The led tester does not drive the leds at a high current and also does not have a protection circuit like the one in the tv.

You need to replace the bad led's or better yet, replace all the strips with new ones.

[beetle1303]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

This will not work, the backlight driver will detect the wrong current and shut down.
The led tester does not drive the leds at a high current and also does not have a protection circuit like the one in the tv.

You need to replace the bad led's or better yet, replace all the strips with new ones.

As the leds are in series in the strips, I was expecting once those bad/opened leds are bypassed and that the strips are basically able lit up, thus should flash momentarily during power up sequence.

For my education, if this is not the case, how would backlight driver detect wrong current?

Thank you.

[R_J]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

As the leds are in series in the strips, I was expecting once those bad/opened leds are bypassed and that the strips are basically able lit up, thus should flash momentarily during power up sequence.

For my education, if this is not the case, how would backlight driver detect wrong current?

Thank you.

The led drive ic drives a mosfet , the mosfet has a resistor from it's source to ground, the currnt through this resistor is monitored by the CS pin of the driver ic. The drive signals (4 in this case) are also monitored by Q7213~q7216 which drive the error signal that will shut down the VCC-INV voltage. There are also over voltage and under voltage detection circuits.

[beetle1303]

Re: Sharp 60LE630M DPS-165HP-2A: No Backlight

Thanks for the detail explanation. I am guessing since there is no flash of led lights, could it possibly because the main logic board already registered the backlight error exceeding limit count and shutdown without even completing the power up sequence?