Picture comes on then goes black within a few seconds. Sound stays on.

Hi,
Power on the unit in the dark room then shine with the flashlight directly in the screen, you will barely see the images. This is because your backlight is not functioning. The following reason was the caused.
1. Power supply - missing B+(supply voltage) coming from this board feeding the inverter board. The B+ produced an out-of-regulation condition and drives it to overload which caused the symptoms. Look for leaky/dried electrolytic capacitor, sometimes it has a bulged/dome at the top but not all, you must have a capacitor checker to determine its condition.
2. Inverter board - even the B+ is good from the power supply, if the fuse, driver transistor, driver transformer is faulty no output to the backlight resulting to black picture.
3. Busted backlight - even inverter board is good but one of the backlights was already busted, it will trigger the protection circuit and will shuts-off the B+ to avoid overload to high voltage transformer.
Diagnosing the fault may technical if you're not handy with electronics. If you don't have necessary tools and test instrument and can't troubleshoot the symptoms yourself, I would advice you to look for an experienced technician to isolate the problem.

Also, check if your unit is under warranty period, avail it because the manufacturer will fix it for free. Don't attempt to open the back cover(it will void the warranty).
Hope I helped you.
Have a nice day!
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