Ok, i dont know if you have experience with this type of repair,,, read below and be sure to understand the tests...
This is a very simple approach.
(OK IF LAMP IS OVER A YEAR OLD IT IS A SUSPECT)
First I would like for you to open lamp door make sure the lamp switch is in the down position, Make sure the bulb is plugged and good, remember if bulb is over a year old it is a suspect, turn unit on listen closely to a wheel start to turn first this is the color wheel and the crackling of the ballast second. If you can here the crackling or see a spark from the ballast it is good and lamp is the suspect. Ok, first would like for you to remove the rear cover, then plug in the set, Now the lamp switch I would like for you to press it and listen for the power supply to click if it does we can say lamp switch is good, next while looking at the ballast, see if it sparks.
If not, power supply and ballast suspect. (Pull lamp out and close the door tightly then turn on unit and listen for the ballast). Also do this test Were the wire is that runs from the ballast to the power supply, make sure it reads around 300vdc if it doesn't you need a power supply if it does you need A BALLAST. You can make sure the capacitors close to the connector are flat on the top if not you may have bad capacitors. It will be easy to see if The power supply and ballast has bad capacitors they will not be as flat on the top as the good ones, this is the problem. Also intermitting shut downs, This can be caused by the lamp switch, make sure switch is in the down position and The thermostat which is on top of the lamp housing, both can be tested buy shorting them out and running TV if any are bad Exchange them and you will be ok, lastly intermitting shut downs, lines in the picture can be the digital board this is a good tip on digital board
Picture of a ballast ,, Capacitor pictures ,, Fan 1 and 2 ,, Lamp switch ,, thermostat, Sensor
Well Good luck friend, and if my efforts on trying to help you save on those large labor charges are appreciated, feedback and a bonus will be appreciated