Spectrophotometer bulbs

The visible-light spectrophotometer we use to measure culture densities has been giving erratic readings lately so I decided to try changing the bulb.  I was happy to find 5 spare bulbs in the folder with the instruction manual (the Redfield lab is PREPARED!), but then very unhappy to discover that, although the new bulb had the right specifications, its filament couldn't be lined up with slit through which the light enters.  The old and new bulbs are the same shapes but their filaments are in different places.

After a bit of cursing I discovered that two of the five bulbs were made by Phillips, and these have the filament in the right place.  The other bulbs are made by Osram; I know the spec bulbs are expensive ($50 or more), so maybe we can send them back.