Magnavox 42 LCD 42mf438b/f7 turns on/off by itself

Pretty easy. Place the monitor face down on a blanket or something like that. Remove the screws on the back of the monitor (there will be about 20). Pull the back off, set it aside and then remove the power supply board. Pop the new one in and put it back together and you are good to go.

Anon, try re programming/setting it up, if that does not work look for a compatible remote.
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About which capacitor you are mentioning about?

If you take back off you should see a problem with the power supply board, caps bulging outward could be 1500uf or 2200uf

The power inverter supply board is bad. Have a tech replace this! Thankyou for asking!

that set is highly rated by users .. it first came out in early 2009 (i think) so you might check to see if any warranty remains ... the display is illuminated by several lamps .. each lamp has its own high voltage inverter .. all the innverters are powered by an output of the low voltage power supply (often 18 volts)... i would suspect a problem with that low voltage power supply.. either a bad capacitor or a thermal issue .. .. ..

Not good. Make sure you have not blocked cooling to TV. It need s air flow. sounds like overheating

Look at the power supply first since it is easier to get to, look for burnt parts, bad capacitors, etc.
http://en.wikipedia.org/wiki/Capacitor_plague
Please post back what you find.

I have exactly the same problem with a Magnavox LCD 42", very similar model 42MF437B/37. I don't have a solution. If you unplug the TV and plug it back it starts working, sometimes for hours, sometimes for less than 5 minutes, before it turns off again. Does anyone have any real solution?