S.B.M.L.

Never heard them referred to as SBML. MBTF was the designation I used to hear them referred to as.

The integral filament is not efficient as a ballast (and neither was it an efficient filament as it had to be underrun to get a good life, and it's in nitrogen atmosphere at not much below atmospheric pressure, required for the quartz arc tube). The lamps were only around 20lm/W, which is same ballpark as a modern halogen lamp and not a lot better than a similar powered regular filament lamp. They were used for street lighting in the area I grew up, only because they retrofitted into standard filament lamp housings and required less relamping at 6000hr life. The old lanterns have long since been replaced by ones designed for more efficient HID lamps, and the main market for MBTF lamps vanished many years ago.

Apparently, Chinese manufacturers have started making them again now, using a halogen capsule for the filament/ballast part, and they are 30lm/W because the filament can run at standard halogen efficiencies.

Thanks for the info.

RE