My Majestic gas fireplace will turn on, but will not stay on. Sometimes it stays on for a matter of seconds... sometimes 10-30 minutes, sometimes an hour or two, before it turns itself off. The pilot light stays on through all of this, just the main flame just goes out. There is no smell of gas when this happens. It usually will NOT light up again immediately, but after a while will light up.

I am not well versed in gas appliances, but am thinking it might be either a venting problem (if not vented well enough, my guess is that the flame will go out, without enough air getting to it) or perhaps a problem in the electronics.. the thermocouple, perhaps? What does that do, and can I replace it? I have been a fairly successful DIYer, but never have messed with gas lines, and don't really want to, but I am thinking the thermocouple can be replaced without messing with the gas line.

BTW - I have manuals and parts lists, but the Majestic website seems to have been purged of anything this old.