Gamma Scientific PMT light meter

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Rich Feldman
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Real name: Rich Feldman
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Gamma Scientific PMT light meter

Post by Rich Feldman » Sat Jun 20, 2020 12:26 am

Got lots of PMT's to look at, but have never biased one myself.
That might be about to change, with an instrument for measuring light instead of counting particles.

This came from swap meet many years ago. Optical head is shown with protective slide shutter and a ratty-looking colored filter out of the way. Box with HV PS and amplifier is shown with connector that fits some unknown module.
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First date code I spied on an internal component is 1973. But the Gamma Scientific brand, of optical reference sources and meters, appears to be flourishing today. A phone call to the office got me to someone in tech support, who has offered to see what he can find in the archives. Too bad that kind of brand endurance and support has become uncommon.

Looks like the pigtail cord between optical head and control unit carries two shielded cables, one for HV and one for signal (both polarities not yet known). The cord from funny round connector has 2 wires for DC power and 3 for, I guess, control inputs and signal outputs.
Coolest thing is the multi-turn rotary pots. Each has three steel balls for planetary gearless speed reduction and slip clutching.
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A peek at the HV generator shows PNP and NPN transistors, reminding me of the flash x-ray units that AS and AS and I talked about last month. I bet the two 51 M resistors in series are part of a voltage regulator function.
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All models are wrong; some models are useful. -- George Box

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