Wow, that Dr. G. Fischer bulb is an oldie!

Fischer quit the business some years ago. Do you have a Fischer P/N (or anyone else's P/N) for the old bulb? It's difficult for me to see the filament in the bulb you've pictured here, but it looks like a C8 filament (axial). I cannot hazard a guess as to the LCL (Light Centre Length, distance from the base reference plane (top of the index pins on the base shell) to the centre of the filament. It is also very unusual to find a shielded bulb like this used in spotlight service.

Can you show us what 50w halogen bulb you'll be substituting? 

Thanks for the clear photos. You will probably actually want to use a 795x rather than a 795. The difference is the orientation of the filament. The 795 you've got has a transverse filament, while the 795x has an axial filament like your original Dr. G. Fischer bulb. It looks to me as if the LCL on the old bulb and the 795 are pretty close, maybe a little too short on the newer bulb, but running a transverse filament in a reflector designed for an axial filament will tend to produce a flattened "bar" of light rather than a round spot beam as will be produced by an axial filament. Also, with an axial filament you've got a great deal more margin for error on the LCL. It can be a few millimetres too long or too short without materially affecting beam formation. The transverse filament, if it is even just a couple mm too far forward or back in the reflector, will grossly upset beam focus. Usually this manifests as a black hole in the middle of the beam.

If you have trouble finding a 795x locally, shoot me an e-mail, tech "at" candlepower "dot" ca .

Finally: Because these bulbs you are using are of higher wattage than the original, please check your circuit (feed wiring, ground wiring, switch) to make sure they are all up to the task.