You might try to call back, explain the situation and then the days leading up to the next tech visit, try to get the problem to surface and leave the TV on for the repair person to see as they walk in the door.
Some technicians might be able to pinpoint the problem, others might have to see it to get a proper diagnosis.
I have had my tv for over 2 years, so the warranty is long gone. I called Samsung and had a tech come out - but they could not find anything wrong... of course it was working fine while they were here. I have the problem that I have seen all over the internet - but haven't seen where there are any solutions. My tv comes on - sound is fine - but no picture, cannot see menu... nothing, just black.
Is there any fix out there for this problem? Preferably one that doesn't cost more than buying another TV?
When I bought this tv - I thought I had found the best one out there. I had done my homework.