Beseler 23C & Zone VI lamp head

Do the Zone VI lamps wear out? Is there a bulb that needs to be replaced? I was given this 23 C enlarger and it seems to work well, but recently used an enlarger at a public dark room and the light source seemed stronger -- printing at F16 and 22 with only 11-12 sec exposure -- far less exposure than what is require for my Beseler/Zone VI lamp head.

Were you printing with a condenser head at the public darkroom?

The "bulb" is actually a tube and yes, they do wear out eventually. They can be a bit dim when using 35mm negatives because a large part of the light output is wasted because it is wide enough for medium format negs (up to 2inch x 3inch I think). I used to use a 4inch x 5inch one and it was dim for 35mm but quite good for 4x5.