Samsung LN47B630 loses LCD Backlight after 1 to 2 Hours

[SilentR]

First post to this forum, I'll try to keep it short. The TV works perfectly for 1 to 2 hours, then screen goes black, sometimes it will flicker on and off 2 or 3 times over a minute or so, other times it just goes off. Sound stays on. My first thought was capacitors, so I checked both ESR and capacity on the power supply electrolytics, they were all fine. DC voltages at the inverter board and connector to mainboard remain steady both before and after the backlight goes off, the only change is the 5v_det pin to the mainboard goes from 5.2V to zero. I assume the inverter circuit is reaching a predetermined threshold and the mainboard is shutting it down. If I pull the connector from the power supply to mainboard, the backlight will come on again for about 3 minutes.

I previously posted this problem on TV Repair Forum, a tech there suggested the mainboard is faulty, but also said it could be the inverter or backlight tubes. Can anyone suggest a way of narrowing down a slowly failing inverter or tube? A used mainboard is over $100, I'm willing to spend that although I'm pretty much stuck with Ebay and the risk I'm going to a bad replacement. I originally was going to junk this TV, but it really is a nice set when it works. If I can fix it, I'll hold out until 4K sets become a bit more established and 4K DSLR's are more reasonably priced. I can send pictures and voltages if necessary. Thanks!

Bill

[SilentR]

Re: Samsung LN46B630 loses LCD Backlight after 1 to 2 Hours

Just thought I'd post the solution to my backlight problem. Turns out it was the power supply. I just couldn't bring myself to throw this nice TV out, so it sat in my basement. My son was given a 46B650 with a minor screen problem, and was happy to get it out of his business space. Mine had an AOU AC03 panel and his was a Samsung SS02, so only the Tcon board was different. I started by swapping the mainboards with no luck, but the PS did the trick.