Another LC-80LE632U 2-5 thread

[budm]

Re: Another LC-80LE632U 2-5 thread

What is the P/N of the SWITCHED LDO regulator IC7504 (4-PIN IC mounted on the heatsink closed to the connector CN7501 PD?
You may have bad switched LDO, https://www.badcaps.net/forum/showth...602#post592602
You need to put a load on it using 24 Ohms 10 Watts resistor on the PNL_12V pin (CN7501 pin 1, 2) to simulate 1/2A load first, it should be ablle to handle 1/2A easily, you can also use 12 Ohms 20W to simulate 1A load.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

It this your exact power supply-LED driver board?
Sharp RUNTKA903WJN1 Power Supply LED Board.
http://www.shopjimmy.com/sharp-runtk...pply-unit.htm#

Yes, that's the one...

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Budm, Thanks for the help! I was able to use a 27W 12V bulb as a resistive load and it lit up pretty good. The current was over 2 amps so I feel pretty good about that one.

Can you help me get the back light circuit operational? I don't have any volts on the collector or emitter on their transistors. I'd have to unsolder the heatsinks just to see what they are.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Hello,
I would have thought that if the Tcon was taking down the 12v line that it would have blown the onboard fuse on the Tcon. Can you load up the 12V line when disconnected from the Tcon with resistors and check it is supplying reasonable current. Power supply problem?
Regards

I don't see an fuse on the Tcon board... i also put a load on the 12V line and got a good 2.25A out of it. When I tried for 4A the regulator automatically shuts down.

[budm]

Re: Another LC-80LE632U 2-5 thread

Something is not adding up, to have the 12V regulator that can easily supplies 2A of current to go down to 0.7V output, it must be really heavy load and cause it to go into over current shutdown.
BTW, what resistance do you get between the 12V pins of the T-CON board and GND PINS?

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Yes, the chip has over current protection built in. I tested it with a 4A load and it shuts down the same way it does when I hook up the Tcon board.

I'm getting 4 ohms on the Tcon power-gnd. It's not a direct short, but still too little to be right. I could hook it up to a non-protected 12V and see which component gets hot

I wouldn't be surprised if the Tcon and the PS AND the display are bad. If the display is bad then I'll just shoot it with a shotgun so no one else goes through this.

So, right now I'm backing away from the Tcon and going in for the backlight. If I can see a working backlight and no physical damage to the screen, then I'll order a new Tcon.

Do you happen to have a power supply schematic? Or know the back light circuit well enough to help me get power to it?

[budwich]

Re: Another LC-80LE632U 2-5 thread

have you tried forcing the system on (with just one cable connected between tcon and panel) using volume up channel down (I think ... but check sequence) while connecting power? It might then clear the 2-5 code in this mode. If you are lucky, back lights should happen. As suggested earlier, check your "labeled voltages" on your power card to see if any are not there during powerinng sequence as some may "disappear" if things are not "happy" so the checks need to look "quickly" in some cases.

[freakaftr8]

Re: Another LC-80LE632U 2-5 thread

You should be able to disconnect both ribbons from the tcon to the panel, do the rest procedure and see backlights.

hopefully the panel is not cracked and the shorted panel took out the tcon board to begin with..

You were able to simulate a backlight load with a bulb and it lit up? This is with the power up.reset procedure?

[freakaftr8]

Re: Another LC-80LE632U 2-5 thread

I have worked on this model and have had the screen completely out of it in the past. This is a full array backlight system not edge lit. Typical problems with most led systems is there LEDs are piggyback or wired in series. One goes down they all go down. LEDs like to either short or open circuit.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

I think the Tcon has a bad BD81000. I hooked it to a bench power supply and it's sucking down all of the 2A the PS could source. The BD81000 was the only device getting warm.

I'm done with this Tcon board for now. I put a bid in on one from Ebay... it's cheap enough to at least try.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

You should be able to disconnect both ribbons from the tcon to the panel, do the rest procedure and see backlights.

I can put the TV in test mode, but there are 0 Volts on the output transistors going to the backlights. That's 0 Volts on the Base, Emmiter, and Collector (all of them). I do have the Tcon board completely removed from the system though... does the main board send a signal to the power supply to turn on the backlight? Maybe I can just source that signal?

hopefully the panel is not cracked and the shorted panel took out the tcon board to begin with..

If it were a cracked panel I would be able to see the damage with backlights up right?

You were able to simulate a backlight load with a bulb and it lit up? This is with the power up.reset procedure?

No... I was testing the 12V regulator with the bulb. It's the 12V line that the Tcon board is shorting out.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Freakaftr8, I have studied your backlight thread... very impressive! Not many people will take on the challenge of disassembling an 80" panel. Kudos!

[freakaftr8]

Re: Another LC-80LE632U 2-5 thread

Thanks. That was quite a challenge.

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Here are the voltages I'm reading on the PS PD connector. This is in service state with Tcon completely disconnected and the backlight cables disconnected. The only thing hooked to the PS is the PD connector going to the main board and the A/C cable.

Does anything stand out? The problem I'm trying to solve is 0V on the backlight LED transistors. There is no datasheet available on the IR2E67M LED Driver so I have no idea if there is an enable pin or what's going on with it : (

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

I see a few posts about OFL being 3.3V when the backlights are up. 0.55V is a suspect level. Is it an output from the Main or output from the power supply? On the power supply it goes through a 22ohm resistor straight to a pin on the IR2E67M... idk why you would want to do that unless it's part of some kind of voltage divider. There are some other resistors hooked to the line... I'll map it out later to see if it helps me decipher if it's an input or an output. Unless someone can tell me? : )

[freakaftr8]

Re: Another LC-80LE632U 2-5 thread

If you unplug the led connectors and try the reset do you get a 1-1 error?

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

There is no Tcon board installed. I'll let you know after a good one comes in : )

[budm]

Re: Another LC-80LE632U 2-5 thread

When you install the new T-con I would leave the ribbon cables between the T-con and the LCD panel off first then check to see if you have 12V Ok, the panel may have caused the old T-con board to fail

[jacksnife]

Re: Another LC-80LE632U 2-5 thread

Ok, got the new board in and it appears to be working... I can see the backlights working from the back. There are no codes blinking, just a solid light.

I suppose there is nothing left to do but hook up the panel now. Should I hook up one ribbon connector at a time or just go for the gusto?

[budm]

Re: Another LC-80LE632U 2-5 thread

So you get backlights without those two ribbon cables from the T-CON to the LCD panel connected? It is not easy to find out if the LCD panel will take out the new T-CO board or not, may be you can unplug the power fast enough.