Sharp LC-70LE745U

[Samantha143]

Hi guys I am breaking my head here and not sure what to do next.
We have a sharp LC-70LE745U that was originally giving us a blinking error code 2 long 3 short and it pointed to be a main board error. We replaced the main board and the error code went away and he front logo turns on regular. Now we have no backlight. We did the flashlight test and there is a faint image. We opened it up and tested each LED strip and they all turn on , we replaced the power board and it does the same thing. Not sure what else to do, any ideas ? Maybe a reset ? Not sure

[Andrew F. Ali]

Re: Sharp LC-70LE745U

Now you can only check EACH individual LED if you dismantled the Panel. What you probably tested was each LED strip, which may light-up as there could be shorted LEDs on the strips that will demand a higher than normal current from the PSU. Therefore, backlight shutdown will occur. If you are sure the PSU you replaced was good then the only diagnostic will point to LED backlight.

[dskall]

Re: Sharp LC-70LE745U

You can connect power and main with panel removed and power it on. The backlights should flash briefly and you can see if they all light or not. Testing individually is not reliable test.

[Samantha143]

Re: Sharp LC-70LE745U

We have the led removed from the back to the front with the boards connected and the logo still turns on the same way but the LED do not light up at all not even a quick flash. We even tested the LED cable that connects to the power board and it works.

[dskall]

Re: Sharp LC-70LE745U

You have panel off and everything connected including leds except panel?

[Samantha143]

Re: Sharp LC-70LE745U

The panel is still basically off but we connected everything to see the LED strips but nothing

[Andrew F. Ali]

Re: Sharp LC-70LE745U

If you don't test each LED individually you'll be going in circles. Remove the glass screen, prism sheet, polarizer sheet, etc. Mark them so that you would know what order to replace them. If you do not have a LED backlight tester, you could use an analogue meter set at Rx1 to test the individual LEDs. You may have to scrape a little bit off the white coating to bet the testing points.

[dskall]

Re: Sharp LC-70LE745U

Can we get some pictures and panel sticker and pictures of led board connector. You may not be getting signal from main board to turn leds on.

[Samantha143]

Re: Sharp LC-70LE745U

Hope this helps. We are testing each LED right now

[Samantha143]

Re: Sharp LC-70LE745U

OK here is an update. I tested each LED individually and they were giving me 2.8 volts each. Tested the strips with the LED tester and it read 92.1 volts to power on. I measured the volts coming out of the power both PB the old and new and they both are giving me 83 volts.

[dskall]

Re: Sharp LC-70LE745U

Can we get picture of connector on power board that runs to main board to see pin legend? Since you get no flash at start up need to see if you are getting signal to turn backlights on

[Samantha143]

Re: Sharp LC-70LE745U

Does this help ?

[Andrew F. Ali]

Re: Sharp LC-70LE745U

OK...So we are sure now ALL LEDs are good.....check the connectors on the strips to make sure they are solid.......Be careful with the reassemble....once everything is back in....give it a try.....GO>...Let it run a few days...see if problem reappear....NOGO>.....Check the BL-ON signal from Main Bd is present......I was almost sure we checked that before....probably didn't.........

[Samantha143]

Re: Sharp LC-70LE745U

BL-ON? Do you mean the little light on the main board ? If so yes it lights up.

[vinceroger69]

Re: Sharp LC-70LE745U

BL ON means a voltage/signal too tell the back lights to turn on if thats missing we need too find out why.It should say on the pcb writing what each pin on the connectors do.There is a pin marked dimmer? in not sure what that one is for

[dskall]

Re: Sharp LC-70LE745U

Ok we Need voltages from connector that goes from power supply board to main board. Will need pin#- PIN DESCRIPTION -Pin voltage in standby-Pin voltage when pushing power button
Format:
Pin# - Pin Description - Pin Voltage standby - Pin voltage power on
1 - XXXXXXX - XXv - XXXv
2 - XXXXXXX - XXXv - XXXv
3 - XXXXXXX - XXXv - XXXv
4 - etc.
Pin 21 maybe bl_on since there is no standard naming of functions

[Samantha143]

Re: Sharp LC-70LE745U

Let me know if this helps .

[dskall]

Re: Sharp LC-70LE745U

Very nice. Unfortunately I am not sure what function last few pins do. Hopefully budm or someone with more knowledge can decipher.

[Samantha143]

Re: Sharp LC-70LE745U

You said pin 21 maybe bl_on and it weird that it starts at 3.2V and drops to .6V on its own ��

[Samantha143]

Re: Sharp LC-70LE745U

Also here are some pictures with voltages that I got from the wiring and to the leds themselves. Also a picture of how the wiring splits. But when I measure the wiring coming from the PS I get 83 from all positives.