Benq DV2680 LCD TV backlight goes out in a minute

[minnie-me]

I need help in fixing this set. After about a minute the backlight goes out. Sound is ok. Power indicator is still on. I checked the usual things, power supply, caps, bad connections, etc. There is no red color in the backlight as you may get with backlight going bad from age. Any ideas or service manuals are welcome. Thanks.

[minnie]

Hold a flash light up to the screen and verify you still have a picture.

BenQ America Corp.
15375 Barranca
Suite A205
Irvine, CA 92618
U.S.A.
Tel: +1-949-255-9500.

[minnie-me]

I tried that with a stronger light and all I see is black. I use that trick with monitors so I am familiar with it. I have a ground, 24 v, 3 volts and around 1 volt going to the inverter board. ground and 24 are the supply. The 1 volt may be the brightness signal. The 3 volt signal only goes to 3 volts when the lamps fire up. After about a minute, the lamps all go out and the 3 volt and 1 volt signal is still there. If I power off and then back on, the backlight comes back on. Off in a minute or so. Audio not affected.

[minnie]

Check the one volt when you first turn it on. It should be around 12.

[minnie-me]

It is 0.5 volts in standby and goes to about 1 volt when turned on. Where does this voltage come from? (which component) I don't have any schematics and its a multi layered board.