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Memorex MLT1921 backlight auto off

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dfsa89:
Hello all,

I have a generic memorex lcd tv. The backlight cuts off within a minute. There are four ccfl, two on the top and two on the bottom. The top two both lights up red/violet and fades to white (bad tubes).

Does having bad tubes normally cause other tubes to cut off?

A picture of the power/inverter board is attached.
Proview Technology Co., LTD
PI-XXXXTLTX Version:B
200-001-XXXXTLTX-BH

860-AB0-190DTLTD-1H

Any help or info is appreciated.

Thanks.

ProDave:
failing tubes is your problem.

Tell us what IC's are used on the inverter, there may be some tricks to stop them cutting out.

billy no mates:
hi
yes ive read in some other post somewhere that bad ccfls can cause it to go off
and a pinky/red tint usually does mean that the ccfl is getting duff
..looking at the capacitors in your pic they dont look bulged but that doenst mean they are'nt faulty


hope this helps
billy

dfsa89:
Thanks for the replies.

Texas Instrument TL494C seems to be it.
Is there any temporary bypass for this ic to test for other possible faults?

The two 8 leg in the picture above is a 4511GD.

Thanks again!

Edit: I have ordered some new tubes.
Edit2: New tubes works fine. Thanks for the help

ProDave:
Can you do some legwork and find a circuit diagram?

There's no simple way to disable protection on this chip, but sometime you can remove a feedback diode to prevent the chip sensing a duff tube, but I couldn't even begin to guess at which diode to remove without a circuit diagram for the inverter board.

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