Test the power adapter to make sure that there is power at the plug (volt ohm meter). Try wiggling the plug while it is plugged into the unit with the power switch on. If it works intermittently it means that the solder joint for the power adapter jack has failed on the circuit board. If that isn't the problem it probably is the power switch that needs to be tested next. IF you aren't confident with disassembling the unit far enough to do the tests you will need to take it in for servicing. Let me know how you make out.