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

[LITEZONER]

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.

LC-50LB481C fallow all this thread but I wanted to be clear on the proper testing procedure for these particular led strips. So black lead to ground, red lead measures 65 or so volts when it settles, check out my picture, non labeled is no power readings, and if I read this thread right it's an open led circuit in the string?

[LITEZONER]

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

LC-50LB481C if I'm reading this correctly, my picture indicates power at the vlet+ but nothing at the vled- if I read this right there is an open led circuit?

[LITEZONER]

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

Sorry for double post.

[budm]

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

LC-50LB481C fallow all this thread but I wanted to be clear on the proper testing procedure for these particular led strips. So black lead to ground, red lead measures 65 or so volts when it settles, check out my picture, non labeled is no power readings, and if I read this thread right it's an open led circuit in the string?

So it settles down to 65V, but how high did it go up to when the TV is turned on before it settles down to 65V?

[LITEZONER]

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

Somewhere in the range of 90s

[budm]

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

So did you keep the meter probe on chassis GND and the LED - pin and watch the meter when the TV is turned on each time?
It sounds like the backlights circuit shutdown the boost converter due to fault detected.
Do you have LED tester to test the each LED string?
Do you see the backlights even come on for seconds?

[LITEZONER]

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

No lights do not come on, you know I tried my led tester on V+ and V- that always seems to work, but not on these for some reason, should I try grounding black lead from led tester to chassis like I did to test the voltages? There was one breif moment when I first got this to try and fix for my daughter's boss (volentold) I disconnected the led strings from the board, plugged them back in and it all lit up for like 10 seconds.

[budm]

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

No lights do not come on, you know I tried my led tester on V+ and V- that always seems to work, but not on these for some reason, should I try grounding black lead from led tester to chassis like I did to test the voltages? There was one breif moment when I first got this to try and fix for my daughter's boss (volentold) I disconnected the led strings from the board, plugged them back in and it all lit up for like 10 seconds.

That means you have open circuit in the backlights if you use the LED tester to test the LED strings but they still not lighting up.

[LITEZONER]

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

Thank you, much appreciated.

[BatsIhor]

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

I have similar problem, except by top LED String blinks, bottom is OFF all the time.

Right after plugging power source my VLED = 63V VLED1=15V VLED2=15V
After Pressing Power button: VLED jumps 91/83V -- top LED string goes on and off every second, VLED1/2=jumps all the time, my meter can't catch any stable value.
I see picture and can hear sound
Video of tv after turning on: https://youtu.be/a4QFZvn47SY

Should I remove bottom LED string and test each LED or there is something else I can check?

[dick_barton]

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

Often if the led voltage peaks as in your post 91/83V and then drops, it does tend to be indicative of a failed led(s) or failed led string connection.

Video of tv after turning on: https://youtu.be/a4QFZvn47SY

Is set as a private video so no access

[BatsIhor]

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

Fixed link, now it's public.

[neilc6]

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

Replace all your strips with new. Turn down the backlight level on all inputs and apps to make the new strips last.