Okay I understand.
The possible causes of this problem are as follows, and I will try to explain the best I can here:
A failing Lamp, which even though producing an image, and no blink of the Lamp light, as well as losing audio can still be causing the problem by causing the ballast to see a hard to drive load and cause the TV to drop one of the power supply outputs. An OEM lamp for this set is around $170.
What can also cause this is one or more out of spec capacitors in the ballast or the power supply for the set. These can become intermittent and cause the TV to have these symptoms as well. Average cost for this type of repair is going to be $250 parts and labor.
The last possible culprit is a failing Light Engine. This is not good news because these sets are known for this failure- and there is an inactive recall for this problem several years back. The Light Engines have a failure that will cause the same symptoms you're having and is almost $1000 for this type of repair.
So, while the most common cause of this is a failing lamp- and any lamp over 2 years old is suspect, the only way to tell is to either replace the lamp, or have a tech measure
voltages from the ballast and power supply to further isolate what is causing the problem.
Sorry there's not a quick fix for this problem today.