Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Thinking this TV is a lemon. Found another cracked screen one on CL (Best Buy Recycles also) and it had backlights but no picture. These TVs were repaired and resold with incorrect and missing parts. The side plate for the connectors and front nameplate are also missing on mine. More concerned about the missing tcon shield which acts as a heatsink.

The 12-A signal is present so not sure the new PS will fix it. TV has multiple problems.

[nomoresonys]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

The StdBy voltage is 12V. DO NOT try to self-test the PSU by using 'a resistor'. You WILL damage your PSU altogether. If you want to self-test your PSU you can take two 1.5V batteries in series connected to the PS-ON and GND.

No duh 420, 1k resistor for 5v, you can test power supply by bridging 12 volt stby to ps-on, comprende? ya

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Got the replacement power supply board in and it's better. No quick backlight flash and backlights stay on during power on sequence. Still no picture though. Guess the tcon is next but think I may be replacing the main board as well.

TV turns on with backlight and will turn off and give me shutdown chime. Just no picture. Fuse on tcon is good and I measure 12V on both sides of it.

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Got a replacement TCON in and finally have a picture but there is a vertical line on the left side and wide white vertical band on the right. Disconnecting the left tcon cable results in a good left side but disconnecting right side cable gets nothing. Confirm this is a bad panel?

[budm]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Panel problem.

[Andrew F. Ali]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

I am so sorry. After all that to get a 'bad Panel'. I would have never guessed, but we did learn a few things along the way.

[zape]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

I have the same TV with no backlight.
St-by light blinks.
I did the flashlight test and see picture, also have sound.
Measured 91v across LED- and LED+ outputs but the measurement blinks, probably because it is PWM signal.
Also measured 63v across LED+ and Ground.

Any ideas?

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

If your backlights flash on power up or dont turn on, they are suspect on any LED tv. If you want to repair tvs, you need to buy a LED tester.

[zape]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Already bought it, waiting for delivery.
So in case it is leds, do you normally replace the strips or individual leds?
If individual, how do you find the right led model and where to buy?

[budm]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Can I see good clear pictures of the whole backside of the TV showing all the board and then good clear straight shot of the whole power supply board?
Is this your power supply board?
https://www.shopjimmy.com/sharp-pltv...-50lb481u.htm#
It has two LED strings with two LED drivers.
You need to keep Black probe on the chassis, Red probe on LED + then turn on the TV to see how high the Voltage jumps up to then wait 10 seconds to see how low it goes down to, then turn of the TV and put red probe on any of the - VLED 1, then turn on the TV to see how high the Voltage jumps up to then wait 10 seconds to see how low it goes down to. Do the same for the - VLED 2.

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

So in case it is leds, do you normally replace the strips or individual leds?
If individual, how do you find the right led model and where to buy?

On tvs where the backlights shutdown (LG, RCA), there are typically 1-5 bad leds. It is better to replace the entire strip since regluing the lens can cause bright spots if not perfectly centered and the correct height. The rest of the leds will have wear and may also fail in the future. I make sure the backlight level is set to 50-60% of max after repair and check all inputs and all apps. If the tv has an ambient light sensor, make sure it is off since this will crank up the backlight in a bright room.

For individual LED replacement, 3V LG LEDs are most common though you can get 6V. Samsung LEDs are typically 3V but reversed from LG ones wrt pads.

You can find strips on ebay and shopjimmy.

[nomoresonys]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

If you don't want to do the whole job over again in 6 months or less on average, replace all the strips, that is if they are the issue. Not that it's a real tough job, it's just the panel is so easily broken, then it's game over.

[zape]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Can I see good clear pictures of the whole backside of the TV showing all the board and then good clear straight shot of the whole power supply board?
Is this your power supply board?
https://www.shopjimmy.com/sharp-pltv...-50lb481u.htm#
It has two LED strings with two LED drivers.
You need to keep Black probe on the chassis, Red probe on LED + then turn on the TV to see how high the Voltage jumps up to then wait 10 seconds to see how low it goes down to, then turn of the TV and put red probe on any of the - VLED 1, then turn on the TV to see how high the Voltage jumps up to then wait 10 seconds to see how low it goes down to. Do the same for the - VLED 2.

Yes that's the board

LED+ voltage starts at 91v and then gradually goes down to 63
VLED 1/2 stays around 0v

I also tested the LEDs with the LED tester and it shows 329v. Like if the led circuit is open. LEDs remain off

[Teknikid]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Hi everyone.

I have this LC-50LB481U model as well. The back-lighting is out. I found on the power supply board the cable which runs to the LEDs. I checked the voltage on all three of the +VLED points and they read 62.9 VDC. I'm unsure if the if the -VLED-1 and the -VLED-2 should go to ground. They have no continuity to ground, though perhaps maybe they shouldn't.

Any feedback would be appreciated.

[budm]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Read post #30 on how to test Voltages on the LED connector with all cables in place.

[Teknikid]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Ok, both +VLED jumped up to ~91VDC, and went back down to ~63VDC. Neither -VLED did anything. They stayed at 0VDC.

[budm]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Well, the +VLED string Anode has about 90 and drop down to 63V but there is Voltage on the Cathode return of the LED strings, this is due to open circuit in the LED string some where. You have the same problem as zape, open circuit.

[Teknikid]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

It's gonna be one hell of an undertaking to get at the LEDs. Any good videos or pics on how to take the TV further apart without inadvertently damaging something along the way?

[nomoresonys]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

This ought to be close: https://www.youtube.com/watch?v=PmFdW9a-kIY

[neilc6]

Re: Sharp LC-50LB481 Two fast blinks Backlight Turns Off No Picture

Just did one. Tricky part is there is double sided tape holding down the panel boards and the panel itself (sides and bottom). I used an exacto knife to cut them free. Lower your backlight level after repair since the default setting for most picture modes is 100%. See this thread as well. https://www.badcaps.net/forum/showthread.php?t=78585