LG 47LW5600 Has picture, No backlight, then I made it worse :-)

[Lawdawg79]

Hey guys, this will be my 3rd TV repair, but my first post. Thanks to this forum I have been able to repair a Samsung 65” and an LG 50” thus far without having to bug anyone. Well I picked up this LG 47LW5600 from a friend of a friend today for free, it had me stumped, then I made it worse.

My test meter is a Fieldpiece HS33

Came home and did the usual (plug it in and lets see what were working with here) thing..

I did the flashlight test and I had picture but no backlight.

Popped the back off and began testing volts at some of the voltage regulator locations, looking for anything obvious on the meter like fluctuations etc...

well i worked in a clockwise pattern around the board and got to the last thing and had a lil back spasm, caused me to jerk just enough I crossed two points and shut the whole thing down. Pretty sure i fried a voltage regulator, hoping thats all it is. So this will probably be a thread I work on for a bit because now I have to replace that before I can diagnose what else is wrong.

Gimme a break though, I have a spinal injury, im just a dummy and forgot to take my baclofen earlier today.... but i remembered after i fried that part.

So, once I figure out what part I fried im gonna need to start diagnosing the board. I believe all the caps are good, or they were aside from that Im not sure where to begin. Im so frustrated im not even gonna look at the board again til ive had an 8 hr reset for myself lol.

Im obviously gonna be ordering some circuit board parts, (regulator), but if im ordering stuff, may as well order anything else I may need. the caps I have on hand arent even close to any on the board but I dont know if I should order any?

like i said, I did have power, I did have image. But there was no backlight at all.

I drew in yellow the area I shorted out. aside from that, i really dont know what else to pick up. For the most part components are pretty cheap so i dont mind ordering a bunch of stuff. Never a bad thing to have some extra stuff on hand anyway.

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Sorry for the extra posts here, those first pics seem to have been degraded by photobucket so im trying again.

[attainteddragon]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

if it a regulator, you will need to know the pinout to live test it. might be the same as the ic above it. heatsink will need to come off to get the part no though. you can check for a short and compare to the other in any case.

it's an lg, so most likely you started with a failed led in the backlight, but you will need to get the ps up and running again before you look at that.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Well when you get it working again I would concentrate on voltages going to your backlight strips

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Oh oh, are those the 12 points inline at the top right of the board? When i went through those i had 2 points with variations. Now, i didnt get the opportunity to go back through and record volts at every point on the board to report here lol. But i want to say 10 of those were putting out 60ish volts, and two were 30ish or 3ish volts, pretty sure it was 3 something..... That is if i am remembering right.

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

it's an lg, so most likely you started with a failed led in the backlight, but you will need to get the ps up and running again before you look at that.

Does that mean the lighting element itself is likely bad?

[attainteddragon]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

looks like you have already started testing the voltage inputs to the backlights and it sounds like you will have led's out, but still, the ps will need to be up and running before you move onto that point.

but yes, panel will have to come out to replace the faulty led's.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Personally on an lg/vizio with backlight problems I go straight to repairing leds and don't waste time troubleshooting power supply. So far no tv I have repaired with failed led backlights has been anything but bad leds.

[vinceroger69]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Have you tested the part you have marked in yellow is it shorted? (you should be able too tset it in circuit too save removing it for now) also check all fuses on the power supply then once you get the psu working again you can re test the led voltages.

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Im gonna have another look today, after i fried it lastnight i had to walk away lol.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Number off it would be nice. Looks like a controller

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Personally on an lg/vizio with backlight problems I go straight to repairing leds and don't waste time troubleshooting power supply. So far no tv I have repaired with failed led backlights has been anything but bad leds.

This is good to know, so i should probably at least start pricing led strips then....are the replacements better than the oem that went out?

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Replacements are used. Better, worse don't know answer to that. I replace individual leds myself. Problem is if you measure current though the leds LG/Vizio run their backlights over 400ma and all LED's I've found are only rated for about 350ma. So they overdrive them. In my opinion it is done deliberately to kill tv to sell more. If this is your tv you would need to lower your backlights as low as possible to reduce current. I sell mine so am learning how to modify led driver to limit current to around 300ma.

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

thanks, good to know. I have thought about buying/fixing/selling. Maybe after this fix I will start to think about it lol. In the past all the issues have been obvious or the fix already found by another. This one not so much....

I took a walk through the board again today. I highlighted the wrong part which I shorted, have circled the right one. I also found a fuse with no continuity, it did have continuity last night before the short, it was one of the first things i tested. So thats on the parts list now.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

It's possible you only blew the fuse

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

It's possible you only blew the fuse

I certainly hope so.

Where do you suggest I look for LED light strips for this thing? Google has too many results, and not all of them seem correct.

Also, maybe my eyes are playing tricks on me, but to me this area on the back side of the board does not look healthy, correct me if im wrong.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Not seeing what you are showing

[Lawdawg79]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

it might just be lighting playing trick on my eyes.

[dskall]

Re: LG 47LW5600 Has picture, No backlight, then I made it worse :-)

Just looks like bottom of transformer to me. Someone else may be able to see something I don't