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PMT drift / PMT standby

>Larry Anderson writes:
>>The procedure that Seamus O'Kane mentioned in his most resent posting I 
>>believe is a good one to follow. Placing a piece of negative in the gate 
>>will reduce the amount of light reaching the PMT's and prevent heating of 
>>the PMT dynodes and anode.

>Seamus wrote:
>We use a black card for this purpose, shutting off all light to the PMT's
>during standby periods. Is this preferable, or is there some benefit to
>allowing some light to pass?

I would think that cutting off all light to the PMT's would be as
problematic as flooding them under hi beam currents. Whenever I need to
dissapear during a continuing job, (like that rare lunch break), I like to
leave the actual session film in the gate. I leave the polarity and beam at
the session setting at all times. This way the PMT's are left on simmer
until I return from El Compadre with a smile. I have never experienced any
drift worth correcting in all three of our URSA equipped rooms, and we do
more weird twisted tube geometry than you will find anywhere. Why do
commercial clients insist on making my tube patch resemble an Rorshach ink
blot ?

Bob Festa                                   Festa at earthlink.net
Director of Telecine                        Festa at holydig.com
Hollywood Digital                           213 465 0101
6690 Sunset Blvd  Hollywood, Ca 90028