Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

Already took it apart for disposal, but there wasn't any obvious damage to the LEDs. Also, the TV wouldn't start without the LEDs or LCD plugged in, so I guess we'll never know. I'm going to just sell the boards now.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

Welp, tried getting at the backlights and ended up breaking the panel.

No big loss though. Thread closed, I guess.

bad news..
you still can run the tv with out panel... to see our suspect was correct about the LEDs

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

Welp, tried getting at the backlights and ended up breaking the panel.

No big loss though. Thread closed, I guess.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

I'll try to do this. The whole backlight flickers evenly so I'm not sure if it's one LED or something else.

It wasn't the power supply, I got another one and the issue persisted.

try measure the voltage on BL sockets , you have 6 groups at least i can see from the photo, each group had one white wire i think its the LED-
so you need to measure with yours meter on mode 200V DC the black probe on chassis and the red probe on each LED+ wire (red/blue/grey) listed your reading over here.

[alfatv]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

1. You can take video, then go frame by frame, sometimes it's possible to see bad LED, it will turn off first.
2. Measure voltages at LED connector when backlight is on and off.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

at yours case nothings better than eyes inspection to check the flickering LED in case one or more dont turn on. but consider the risk of yours screen size by disassembling.

I'll try to do this. The whole backlight flickers evenly so I'm not sure if it's one LED or something else.

It wasn't the power supply, I got another one and the issue persisted.

I'd rather avoid disassembling the panel, but is that the next best step besides replacing the t-con or main board? Also, is there any way to start the TV without the backlight connected? I tried disconnecting them but the TV refuses to start without them.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

How should I check the backlight, and where do I get a replacement?

at yours case nothings better than eyes inspection to check the flickering LED in case one or more dont turn on. but consider the risk of yours screen size by disassembling.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

from yours PSU photo, you have only 1 transformer between the HOT & COLD side, this mean to me that any issue at LEDs backlight strips will effected the currents at other rail such the main 13V. and in reverse wise if there issue at rail 13V will effected the LED BL, in this case we go first to check the cheap option which are the BL.

How should I check the backlight, and where do I get a replacement?

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

from yours PSU photo, you have only 1 transformer between the HOT & COLD side, this mean to me that any issue at LEDs backlight strips will effected the currents at other rail such the main 13V. and in reverse wise if there issue at rail 13V will effected the LED BL, in this case we go first to check the cheap option which are the BL.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

Update: The audio-out port also stops working when the rest of the audio stops. I fear it may be an issue with the main board.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

at which resolution..?

1920x1080, I'll try a usb movie once I reassemble the TV.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

well, i think the best way copy movie on usb flash drive and play it direct on the tv.. to terminated any out source could be the reason.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

The sound issue occurred over both HDMI and 3.5mm, I've been using this with a PC and laptop. I've got a new power board and will test that, I suspect it might be an issue with something that powers the 13V rail which seems to power the speakers.

at which resolution..?

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

cutting the sound could be happened as i think because you were using the tuner as source... if you use HDMI signal or usb media it will not happened.

spark will effect on signal of tuner. if this signal disrupted it will cut sound... look like bad receiving areal signal. if you use external signal such HDMI or other i mentioned before... i dont think the sound will cut off. just the led will keep flickering as you have now... try and test.

The sound issue occurred over both HDMI and 3.5mm, I've been using this with a PC and laptop. I've got a new power board and will test that, I suspect it might be an issue with something that powers the 13V rail which seems to power the speakers.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

Where should I look, and what's the process for checking the LEDs? And why would this cut off the sound at the same time?

cutting the sound could be happened as i think because you were using the tuner as source... if you use HDMI signal or usb media it will not happened.

spark will effect on signal of tuner. if this signal disrupted it will cut sound... look like bad receiving areal signal. if you use external signal such HDMI or other i mentioned before... i dont think the sound will cut off. just the led will keep flickering as you have now... try and test.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

LED flickering never being powerboards neither mainboards. or bad soldering too..the LED self are the issue.. one or more of them have spark , which result complete picture flickered and sound cut off too , later on let the reset LED Flickered even at low backlight level. it could be too at one of its sockets behind the screen

Where should I look, and what's the process for checking the LEDs? And why would this cut off the sound at the same time?

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

At this point I've bought a cheap replacement power supply just to test if this one is the problem. I'm hoping it's not the main board.

LED flickering never being powerboards neither mainboards. or bad soldering too..the LED self are the issue.. one or more of them have spark , which result complete picture flickered and sound cut off too , later on let the reset LED Flickered even at low backlight level. it could be too at one of its sockets behind the screen

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

LED pinout:


Pinout to the board:


At this point I've bought a cheap replacement power supply just to test if this one is the problem. I'm hoping it's not the main board.

For anyone interested, I'm using this manual.

[Diah]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

you wrote " at lower brightnesses, the screen backlight flickers randomly"

can you upload focused clear photo on the label print chart of the backlight sockets L1 & L2 on the powerboards.

[TheForgottenKing]

Re: Sharp LC70LE755U - Intermittent backlight flickering and loss of sound.

I've attached images of the power supply, main board, and tcon board respectively. Please do specify if you want a closeup, but I don't see anything immediately obvious.