The first thing I'd look for is a failed electrolytic capacitor in the internal power supply circuitry. Often these can be spotted by visual inspection - the top of the capacitor is bulged out and may have leaked material. (Generally, these are aluminum cylinders about 8-15 mm diameter, 10-25 mm height, with a plastic sleeve marked with the capacitance, voltage, maximum temperature rating and brand name.) It is not unusual for more than one capacitor to fail before the unit quits working - the worst case I've had was 13 bad capacitors in one TV set (although the set was getting flaky a long time before it stopped altogether).
The replacement part usually costs less than a dollar from the major electronic component suppliers. Don't get too cheap; you want one rated for at least 5000 hours at maximum temperature, and with a good ripple current rating. The Panasonic FR series works well for this application.
on Jul 14, 2015