Lg 50pc3d

[ljintexas]

Initially dead as a rock. Replaced a dozen obviously pregnant electrolytics on smps and now have standby led and powers up. Vs and Va match label now at 60 and 193 all the way to Y sustain. Fuses on Y sustain good. I get this orange vertical band that moves every three seconds across the screen. If I push Vol button, it causes wider blue and white band in center of screen for a few seconds, then returns to orange band cycling across the screen every three sec or so.

[Alastair E]

Re: Lg 50pc3d

One of the three MOSFETS on the Buffer-Boards is short.

Just replace all three.

[ljintexas]

Re: Lg 50pc3d

Is there more than one buffer board and where is it/they located? Thank you sir for lending your expertise.

[Alastair E]

Re: Lg 50pc3d

Buffers are extreme l/h side connected to ribbon-cables of panel.

All parts are on reverse-side, so you have to remove them to see. take care of the orange ribbons, they are not very strong, once damaged--set is toast.

[ljintexas]

Re: Lg 50pc3d

Thank You sir. I appreciate the assistance. I will remove boards and test MOSFETS.

[ljintexas]

Re: Lg 50pc3d

MOSFETS on upper board shorted..noticed two shorted MOSFETS on Y sustain as well. It shows signs of the IPM being very hot. I understand IPM is replaceable, but, I don't know that this set is worth the additional investment. I also see crack in one ribbon cable on bottom buffer board. I think I am going to throw in the towel and salvage the rest of the parts.
I am disappointed..

Thanks for your assistance.

[Alastair E]

Re: Lg 50pc3d

Just replace those MOSFETS. Cheap and easy--Might as well give it a try.

IPM's always run hot and discolour the boards. You could always fit an old PC fan to 'em...
Worth also replacing the small SMD caps around the DC/DC converter that generates the Gate supplies to the IPM's If these are low--the IPM's more likely to overheat/die

I doubt the Y-SUS is seriously faulty--or you wouldn't be getting that image....

If that crack in the ribbon isn't cutting any conductors, just be careful with it, It'll be fine, As far as I see, there were no horizontal lines on the image which could indicate a ribbon problem.

[ljintexas]

Re: Lg 50pc3d

There is now a horiz black line about one inch wide in line with the ribbon that has the crack in it...it must have cracked in the course of my removing and testing the lower buffer. I was as careful as I could be..must be brittle..furthest from cooling fan...I fired up the set without the upper buffer installed and got the same result on the lower half of the screen..this prompted me to check Y sustain.

[Rider]

Re: Lg 50pc3d

I have the same TV that I just repaired for me it was the lower buffer board Mosfets
here's how to check them http://blog.coppelltvrepair.com/2010...-lines-in.html
Just a piece of advice don't run the TV for a long time with the back cover off
the Y-Sus and X-sus get REALLY HOT! I point small fans at them while the cover is off

[ljintexas]

Re: Lg 50pc3d

Unfortunately, I have a cracked ribbon cable that produces a one inch tall horizontal black line close to the bottom of the screen. Upper buffer has three shorted MOSFETS. Y sustain has some bad components as well. This set has a built in 12 in wide low speed squirrel cage style cooling fan built in.

[ljintexas]

Re: Lg 50pc3d

I think the Y sus may have killed the upper buffer board..in any event, with a cracked ribbon..it's a source of parts now.