The first thing to do is eliminate all possibilities other than the TV. If you have a source like a cable box connected to your TV, switch it out with a DVD player or some other device you know is in working order.
I have seen cases with Protrons where they will change inputs on their own giving you a blue screen as if no source is connected or giving a "no signal" message no matter what you connect to it. The first thing to try is to leave it unplugged for a minute with the power button held down to try and reset the TV. Holding the power button is not a reset procedure, you are just trying to drain out any capacitors that might be holding a charge when the set is unplugged. I have not been able to determine exactly what causes this symptom. I suspect it is a problem with the main board but have not seen any fixes that traces it back to a common component. Parts are also difficult to get on this set so a repair might not exist. If you can find a local repair shop with an inexpensive bench fee to bring it in you might try that. You are hoping they can locate a defective component like a capacitor that is bulged letting noise through or dipping a supply.
Unfortunately I do not have consumer contact information for Proton or Spectroniq, the company name it seems to have taken. All information available is out of date or not in service.