Help with Sharp TV - LED driver board etc...

[petervfx]

Hi there, first time here so be gentle (long time lurker though)

I am not highly skilled in these matters - I only put my own computers together and did one very basic soldering job for my car. Probably don't need to solder for this thing anyway.

My 70" Sharp TV LC-70LE632U developed a problem after I went on a trip and disconnected power to my TV for seven days. Upon return, the TV would not power on, only 2-5 code (12V PS problem).
After changing all boards (t-con, main board, PS board in that order), I got rid of the code, and TV comes on, has sound but no picture. I did a flashlight test, and I can see that LCD panel is producing the picture but no backlight. There is no code. Tried powering it up a few times, even with the VOL- and INPUT buttons pressed as I plug it in the outlet, and no difference. The TV comes on as if everything is OK, but the backlight is not ON.

Now, in the service manual it says to replace the "LED driver board", except - I cannot see that board on the back of the TV! There are only three boards here, and I even see the four screw holes exactly the shape and size of the LED driver board, but no board. The only explanation would be that the board is under the metal backing. Is that possible? Why would they place it in such a hard to reach place??? Here is a youtube video that shows what the back of the TV looks like with the cover off (mine is a different model, but looks almost exactly the same - same layout and same boards and same sizes)

https://www.youtube.com/watch?v=peI2UdCv7fI

You can see the t-con board on the bottom, power board above it, and main board to the right. No LED control board visible at all.

More questions:

1. This is a 70" TV (about 110lbs) and so far I have been working with it on its stand, with the plastic backing removed. Can I continue to work that way, even while trying to access the LED driver board?

2. I am looking for the LED driver board for my TV, and in the service manual it says that the part number is RUNTKA842WJZZ , yet, when I find it on e-bay, it is always listed for LC-70LE733U and never for my model which is LC-70LE632U. But part numbers are the same. Should I just bite the bullet and order it anyway and install it? My model (le632) is full array LED, and le-733 seems to be also...

Thank you!

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

The plot thickens:

I just realized that my model of the TV does NOT have a LED control board!? I am looking at the service manual overall wiring diagram, and model 633 has an LED ctrl board, but model 632 does not.

Any ideas what is wrong here? I would hope that the old broken PS board did not burn all LEDs, that would quite a feat... there are hundreds of them as it is a full array TV...

[Andrew F. Ali]

Re: Help with Sharp TV - LED driver board etc...

Check the connectors and verify they are inserted correctly. look at the underside of the connectors on the PCBs and verify all are connected/attached to the PCB and not pushed out. Verify yo have voltage on the connector to the backlights..........

[budm]

Re: Help with Sharp TV - LED driver board etc...

Is this the board you have?
http://www.shopjimmy.com/sharp-runtk...upply-unit.htm

That is the power supply/LED driver board combo.

[freakaftr8]

Re: Help with Sharp TV - LED driver board etc...

The way that these TVs are configured even sharp LEDs mostly all LEDs are wired in serie. If one LED goes out in the array no LEDs will work. However usually the TV will shut down with an error code normally it's one fast one short blink on the inverted V.

You very well could have a power supply failure

[budwich]

Re: Help with Sharp TV - LED driver board etc...

If you pull the connectors leaving the Tcon board going to the panel, I do believe the panel should light during part of the initial startup. It may take a couple of tries. The other check would be to measure the voltages going out of the top cable on the power board towards the panel (led drivers?).

Lastly, when you say you replaced all the boards, was that with "new boards" or "recycled boards". If they were "recycled", it is possible that you have a power board failure still.... maybe. Try swapping back the old power board along with doing the tcon cable suggestion.

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

I've checked all connectors and they are all as they should be, even the thin ribbon cables - I made sure they are seated properly in the little groove...

However, I have not taken any measurements yet. I am not very experienced in these matters, and am afraid of shorting something. But may try when I feel more adventurous.

Budm, yes that's exactly the power board! I replaced it with a "new" one, which was hard to find, from a TV repair store in Canada. Other boards were also bought from a place that rips them out of TVs with broken screen (usually broken in shipping) so no guarantees that they work either...

I already put my original t-con board back in place, and still the same problem, so at least I eliminated that as a possibility (I hope). Either it is the power board or the main board. Unfortunately, when I pulled my original main board, one of the surface mount caps got pulled off - it is still holding on the board, but merely by a hair and only on one side - the other is clearly disconnected... wonder if that can be repaired so that I can put that back and see if the TV comes back to life?

I am thinking that it may be better to somehow find which components on my original boards failed and replace those, than use "new" boards which may be broken.

I would like to test the voltage going from the PS board to the LEDs via two cables at the top of the TV but don't really know how to do it. Any suggestions, and/or warnings? I don't want to fry something...

[budwich]

Re: Help with Sharp TV - LED driver board etc...

You might get some info out of this thread on a bigger set of the same "line".

https://www.badcaps.net/forum/showthread.php?t=31895

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

I just glimpsed to it, but two things are important: I already tried soft reset with VOL down and INPUT button; I tried some others too (like holding power while plugging it in) and nothing.

The problem is actually not that I have a code any more. Since I replaced the power baord I have no codes. The TV comes on normally as it should, and I can turn it on and off. It behaves just as it should, with one little exception - the backlight does not come on. Other than that, it's all good.

[budwich]

Re: Help with Sharp TV - LED driver board etc...

OK... but you likely need to do more than "glimpsing"... :-) Anyways, I am not sure that the soft resets are the same for all set (ie. sharp). Further, I think the one soft reset is vol down and input while plugging in... not sure if your statement alludes to this correctly.

Further, as indicated in the thread, there might have to be a reset of the error counter that's in the service menu.

Still further. When you say "I already put my original t-con board back in place, and still the same problem"... you need to be specific about the "same problem" even if it means restating the "observation". The reason is your "problem" has migrated from codes, to no codes, to blank display, sound. Based on your testing, are you now "implying" that if you put in your original PD and TCON card, you do not get any codes or you have indeed tested this scenario?

As suggested, I would pull a TCON cable (going to the panel) and observe carefully what happens.

Further on your old board, you might try "needling" on some conductive glue/cement adhesive to glue the contacts back in position. I haven't done this but I can't see why it won't possibly work.

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

OK... but you likely need to do more than "glimpsing"... :-) Anyways, I am not sure that the soft resets are the same for all set (ie. sharp). Further, I think the one soft reset is vol down and input while plugging in... not sure if your statement alludes to this correctly.

Yes, that's what I did, although it did not seem to be necessary - as soon as I changed the PS board, the 2-5 code went away and the TV was back to normal operation, except - no backlight. I got the code from the service manual.

Further, as indicated in the thread, there might have to be a reset of the error counter that's in the service menu.

I will check for that today and will let you know what I find out. But considering it starts up normally, I have doubts...

Still further. When you say "I already put my original t-con board back in place, and still the same problem"... you need to be specific about the "same problem" even if it means restating the "observation". The reason is your "problem" has migrated from codes, to no codes, to blank display, sound. Based on your testing, are you now "implying" that if you put in your original PD and TCON card, you do not get any codes or you have indeed tested this scenario?

The problem started as the 2-5 code (no 12V). I tried resetting the TV with the VOL- and INPUT while plugging in the power cable and nothing. It appeared like the TV tried to do something, twice but eventually, it would come back to code 2-5. I then changed t-con board first, the problem stayed - same 2-5 code. Then I changed the main board, and the code was 1-1 at first, but then changed to code 2-5 when I plugged it in once more. Then I changed the Power Supply board, and the code 2-5 went away. The TV started normally, and was not giving me any more codes any more. The sound is there, but the screen is black and with a flashlight I can see that the LCD is working and has the picture, just no backlight.

As suggested, I would pull a TCON cable (going to the panel) and observe carefully what happens.

I was trying to see if there is ANY light leaking anywhere, and from what I see, there is no light at all. Its like the LEDs are not coming on at all. (if that's what you want to check with pulling the t-con cable)

Further on your old board, you might try "needling" on some conductive glue/cement adhesive to glue the contacts back in position. I haven't done this but I can't see why it won't possibly work.

I am sorry, but I don't quite get it... Do you mean i should just check all kinds of contacts on the board especially where there is glue?

[budwich]

Re: Help with Sharp TV - LED driver board etc...

"I am sorry, but I don't quite get it... Do you mean i should just check all kinds of contacts on the board especially where there is glue?"

No... you said one of the component on the original board fell off. Use a needle and some careful / fine eye work and glue it back in place with some conductive adhesive. That is likely the only way you are going to repair a surface mount board, if at all.

As for the TCON disconnection, it may allow the system to "boot" in some form and attempt to light the leds even for a second. IF it doesn't, try a few more times. Further, a code may show up / something.

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

"I am sorry, but I don't quite get it... Do you mean i should just check all kinds of contacts on the board especially where there is glue?"

No... you said one of the component on the original board fell off. Use a needle and some careful / fine eye work and glue it back in place with some conductive adhesive. That is likely the only way you are going to repair a surface mount board, if at all.

As for the TCON disconnection, it may allow the system to "boot" in some form and attempt to light the leds even for a second. IF it doesn't, try a few more times. Further, a code may show up / something.

Ok, got it So surface mount components are THAT hard to repair? I was fantasizing about just putting a touch of solder there and fixing it that way - would that not work?

Thanks for the suggestion, I may try that. I was thinking of also finding out where I could measure the voltage going from the PS to the LEDs, as there are two cables... I am thinking that perhaps the "new" (probably repaired as it had scuff marks and such), PS board may be defective and since power to LEDs goes straight to them, there would be no code (no CPU of any kind between PS board and LEDs so no way for the TV to know).
I hope I am making sense.

[budwich]

Re: Help with Sharp TV - LED driver board etc...

It is likely you will vaporize your SMC before you get it solder. :-)

The main problem with PD boards that I have found in my limited travel is that almost all the service manual DO NOT provide any and / or limited information on the boards. Not sure why. I think you under estimate what signals are flowing between boards... just because there is no direct connection, doesn't mean that the faults can't be detected by other components and set accordingly. Having said that, I don't know with any confidence that there is. Your problem may be either a failed LED (singular -> because of series) or "commanded shut down" because of control issues.

Again, pull one of the tcon cables and see what happens.

[freakaftr8]

Re: Help with Sharp TV - LED driver board etc...

I got an idea shine a flashlight into the screen and see if you can see the screen working but no backlight

[budwich]

Re: Help with Sharp TV - LED driver board etc...

I got an idea shine a flashlight into the screen and see if you can see the screen working but no backlight

I think he said he did that and can see that there is an "lcd picture" but no back light.

Freakaftr8, on one of your sets (quoted a post herein), you were trying to get access to the service menu to reset the error counter. Were you ever successful in that effort... someone was helping you with the service mode access.

[zlw1]

Re: Help with Sharp TV - LED driver board etc...

If you can get rid of the 2/5 code with a new power supply, it's a defective backlight or shorted panel itself.

[zlw1]

Re: Help with Sharp TV - LED driver board etc...

Here are the steps you should follow.
The 2 and 5 blink code indicates Panel 12V failure – defective T-Con, Power, or defective or cracked LCD display. Please disconnect the FFC cables between the T-Con and Panel and then power the unit on - if it comes on with backlight and there is no physical damage the to the LCD panel, the panel is defective; if however, the blink code continues, replace the Power Unit.

[freakaftr8]

Re: Help with Sharp TV - LED driver board etc...

Here's a possibility. You may have gotten a bad power supply the power supply if there's an LED conflict should throw a 1 1 error. Since its bypassing and overlooking it and powering up with the display working now it's tell me that originally you had a power supply error now your T CON is working but your power supply is not. There's 2 different symptoms going on here first you said that you had no picture and you had a 2-5 error that significantly points.to a tcon problem or a panel problem so then if you were to put your original t-con back in your TV I bet you would have a to 5 error again. I would replace the power supply again or ask for an exchange

[budm]

Re: Help with Sharp TV - LED driver board etc...

@PETER, So I tested out your board, the 12VPNL output is only putting out 7VDC instead of 12VDC. It has bad Q7120: KIA378R12PI so you need to get a new one.
I just placed an order from EBAY.