That sounds like the entire television is shutting down. Do you still get audio when this happens?
Sounds like you'll need to invest in a decent multimeter. Head down to the Kent Harbor Freight and buy the multimeter that isn't a clamp-on, and certainly not the one that is usually $3:
http://www.harborfreight.com/ac-dc-d...ter-37772.html
This meter has everything you'll really need for tv repair work. 20 bucks is a steal for this meter, too. At any rate, get a meter, and we'll walk you through some basic B+ voltage checks.