How to tell when lamp is burned out?

I was wondering if anyone can tell me if there is a way to tell if the lamp is burned out by looking at it?  My husband follwed the directions posted in this forum about cleaning the dust out of our 2200mp projector.  The first time it went great, no problems.  When he did it a second time (very carefully) several months later and plugged the unit back in it would no longer come on.  No lights at all not even the standby or lamp light.  He thought maybe the lamp was the problem but it worked fine before he cleaned it out, the lamp light wasn't on and there wasn't any popping sound.  The bulb looks finem, the filaments are not broken and there are no burn marks.  He is concerned that he will spend the $300 to replace the bulb and find out that the unit itself is bad and then be out the $300 for the lamp.  Since the unit was not in use when it stopped working, how can you tell if it is in fact the bulb?  Thanks for any help you can give.  And by the way the unit is no longer under warranty so that isn't an option.