23C Dual Dichro lamp won't illuminate

I was recently gifted a Beseler 23C II XL with the Dual Dichro head. When I power it up, the fan in the head comes on but the lamp doesn't. I've inspected the bulb and it looks fine (filament is intact). The contacts *look* clean and I have removed and reseated the bulb. Any suggestions as to what the problem might be? It is otherwise in excellent condition with all the glassless carriers other than the 35mm slide carrier.

There is a lever on the right hand side used to move the filters out of the way, which when pushed to the back engages "paper saver" mode. Make sure it is pulled all the way to the front. Also make sure the lamp house is completely closed, as there is a switch associated with the twisty-turny knob. If that doesn't help, I've had numerous times where the bulb died but you couldn't tell by looking at it.