Camera tube display

[dtvmcdonald]

"Ordinary" PMTs, of which the 931 and similar ones like the 1P28
and even the ones with the photocathode on the front glass,
are not permanently damaged by room light, and the 931 and 1P28
won't be by even straight sunlight. That's turned off of course.
Far red multialkali ones might be by the sun, but I've never seen it happen,
and I've used hundreds of these things.

However!! They can "charge up" and take hours, or for the red ones
even a week or two, to fully recover their original low light
dark current performance. Just let them sit in the dark for an hour
before using if you're fussy.