Sharp LC-40LE550U No Sound,Video and Blacklight

[Eugenio1991]

Hi Members ,

I'm New to this Forum and this is my first post. I'm hopping it goes good and that this experience will help me learn something new.

OK lets get to the facts.

The TV that I will be working with is a Sharp LC-40LE550U.
So far I've tested the power supply and the main board.
but I'm I need help on what these Voltages mean. First time

Power supply model: Sharp 9JY0940CTJ05000 (FTPL-009) Power Supply Unit.

please see attachments for data.

Thank you.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Your main board is not sending out BL-ON signal to turn on the Backlights circuit, this can due to ACD (AC DETECT) which monitor the AC feeding the TV to see if it is within the operating range or not, if it is not, the the ACD signal will be <1 V, if AC is good the ACD signal will be >3V.
The ACD circuit does fail a lot in Sharp TV due to bad Opto Isolator or the resistor feeding the Optoisolator have drifted in value so the Opto is not fully turned on.

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Thank You Dudm.

So in other words I need to replace the MainBoard or the power board?
Where can I test the bad Opto Isolator or the resistor feeding the Optoisolator?

How would I go about testing or going Forward..Im new to this and this is my first time fixing and LCD Tv.


(Sharp 9JY0140CTJ05100 (FTIF-020) Main Board for LC-40LE550U)
http://www.shopjimmy.com/sharp-9jy01...c-40le550u.htm

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

I need to trace out the ACD circuit on that power supply board to be able to give you the test points.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

OK, disconnect all the cables to the power supply board except the power cord, but do not plug the power supply cord to the outlet yet.
Short pin 3 and pin 4 of the Opto UM107 together.
Attach DCV meter with black probe on the chassis, red probe on the ACD pin then plug in the AC cord to see if the ACD pin will now show around 3VDC or not.

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

OK, ill get started.
ill report back in a bit.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Never mind, I found the service manual for this model, the normal condition of the ACD pin is LOW, it is part of the backlights shutdown circuit not the same as AC_DET as I thought.
So back to the main board problem for not providing the BL-ON signal.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

You can try forcing on the backlights circuit by first disconnecting the BL-ON wire going back to the main board then use 220~510 Ohms resistor between BL-ON pin of the power suply and the 3.3V standby pin to see if you can get the backlights to come on and able to see the pictures on the screen or not.

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

So what I understand is that the power supply board is in good condition and the issue is the main board cause its not sending the signal to turn on the backlights?

ill see if a can find a 220~510 Ohms resistor and try what you mention above and will report back.

How would a test the tcon board to see if its getting power?

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

So what I understand is that the power supply board is in good condition and the issue is the main board cause its not sending the signal to turn on the backlights?

ill see if a can find a 220~510 Ohms resistor and try what you mention above and will report back.

How would a test the tcon board to see if its getting power?

So far it looks like the power supply board is OK but you should test the backlights to see if they are OK or not by using the force on resistor as I suggested.

There should be a small SMD fuse on the T-CON that you should test to see if you do have 12VDC at both ends of the fuse with ref. to GND.

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Ok I got the resister and follow what you told me. And I was able to get the back lights on.
But I still don't get any image or sound. I also checked the fuse on the T-CON board and read 0. I think that I need to replace the main board. What do you think?
Or what do you recommend going forward.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

So not only that the main board is not sending the BL-ON tO turn on the backlights, it also has other problems as well since if we only have only problem with BL-ON then other functions of the TV should be fine but they are not, so you need new main board at this point.
Do you know the history of the TV?

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Here are some pic.

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

I see at least two 3-pin regulator IC's, u7102, 7107 taht you may want to check the Voltages on all 3 pins.
You may also try heating and cooling the board too to see what will happen.
The board is about $90 at shopjimmy but he is out of stock right now, it may be common failure board. It is not to spend $90 on this 40" TV since we also know about the possibility of bad connectors for the LCD strip also in the other thread.

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

No. I bought it at a Good Will Outlet.
I saw that the LCD screen was not broken/crack so a decided to buy it, so that I can Learn how to fix Tv's and since I need to upgrade from a 32in if I got it fixed.
I also notice it gives power to a USB when plugged and it has voltage to the output of the speakers and the standby and the button work. It's weird. Any place you will recommend to buy the mainboard.

Also to mention I had to break an old radio to get a resistors. Lol

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Can you point out where are the IC's

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Ok I found them.
U7107
Pin-1 _ .2
Pin-2 _ 1.5
Pin-3 _ 3.3
Pin-4 _ 1.5 (big one)

U7102
Pin-1 _ 5.2
Pin-2 _ 3.3
Pin-3 _ 2.0
Pin-4 _ 3.3 (big one)

[Eugenio1991]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Hello Everyone. I just order a New Main Board from Ebay for about $60.

But can i get help on deciphering the NC circuit i get 0 volts?
Also not sure if the 3-pin regulator IC's are they getting the correct volts?

i would like know for learning purposes.

Thank You!!

[budm]

Re: Sharp LC-40LE550U No Sound,Video and Blacklight

Ok I found them.
U7107
Pin-1 _ .2
Pin-2 _ 1.5
Pin-3 _ 3.3
Pin-4 _ 1.5 (big one)

U7102
Pin-1 _ 5.2
Pin-2 _ 3.3
Pin-3 _ 2.0
Pin-4 _ 3.3 (big one)

if you look at the regulator IC U7107 with big tab up, the left pin is the ADJ/ or GND if it is fixed output regulator, in your case it looks to be ADJ pin, middle pin and the big tab are connected together internally and they are output pins, the right pin is the input pin.
So if ADJ has 0.20V then you add 1.25Vref then the output should be = 0.20 +1.25 =1.45V +/- 3% so U7107 has correct output Voltage.

I am not sure if you look at the U7102 correctly or not but it looks like it has 5V input and out of 3.3V which sounds about right.