Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Davy on October 27, 2014,10:47:26
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LG 37LC46 No back light, led goes to red after 5 seconds.
Looks as if the all in one psu and inverter board had their caps changed recently, with 'upped' voltage ratings, the main dc voltages appear to be correct and 'hash free'.
The back light control chip is a FAN7382, pin one has 15V Dc whilst it's mate has 19V on pin 8, the H out on pin 7 doesn't seem right, it looks like a row of spikes with smaller ones between, an identical waveform also appears on pin 8. The center of the push pull FET goes to the HV transformer primary then down to deck via a 1uF metalized film.
The top FET has the full rectified mains on the drain whilst the bottom FET has only about 14V on it's drain. No HV.... nuffin! I can only think of the 'Fan Chip'.
Anyone had problems with no back light in this LG brand of 'LC' telly's, am I missing anything or anything I should know about?
Dave
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Hi Dave,
Most probs I've had with these were the caps, about 10 of them, but that was for the tv struggling to come out of standby. The FAN IC has been known to give problems too. I've changed a couple but can't recall the symptoms.
Bruce
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Thanks for the quick response Bruce.
Think I'll try one in, the w/f sure don't look right, didn't measure its amplitude wasn't all that great come to think, I did a post thinking there might be another answer I didn't know about.
Bring back the good old day's when Grumpigs (Grundig) used to include a schematic in all their telly's, come think B&O did the same.
Will get back with the results should I manage it, thanks again Bruce, regards
Dave