[old_tv_nut]

When I worked on the CBS/Motorola EVR video player, we noticed that the Hamamatsu PMTs were less noisy than the RCAs, but would become equally noisy if exposed to fluorescent lighting.

I do not know or recall if the output decreased and the extra noise came due to turning up the dynode voltages.

I do not know if they recovered after some time, as we did not re-use the degraded ones and carefully replaced them with new PMTs in a relatively dark room. The players were demo units, so we wanted to cherry pick the least-noisy units.

I speculated that the Hamamatsu PMTS were assembled and packaged in a dim environment and the RCAs came "pre-exposed," but I have no actual knowledge of that. Photoemissive materials are so open to degradation that it could easily have been a difference in processing, not light exposure at the factory.