Film-Tech Forum ARCHIVE: Dolby Digital Having Basement Reader Problems?

This is topic Dolby Digital Having Basement Reader Problems? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Joshua Waaland (Member # 287) on 02-11-2006, 07:37 AM:

I went to see Narnia last night at the theater I used to work at. I noticed when I looked into the booth that they had the Dolby Digital penthouse readers on the Christie P35GPS heads. When I was there a few years ago, we just had the basement readers and I don't remember them being a problem. Did something happen at some point with Dolby that would make them go to a penthouse reader? Was there a high failure rate with the basement readers or something?

Posted by Mark Gulbrandsen (Member # 72) on 02-11-2006, 10:11 AM:

quote: Joshua Waaland
Was there a high failure rate with the basement readers or something?

Actually none of them worked reliably because there is so much jitter induced by the P-35 projector itself that the SRD processor could not deal with it. So most of the basement readers were replaced by Penthouse readers. It was not the fault of the basement reader itself though. The latest incarnation of the Christie and its basement reader work perfect though... they've now gone to round tooth metric drive belts and a much simpler film path. No more double sided timmiing belts!

Mark

Posted by Monte L Fullmer (Member # 2797) on 02-11-2006, 02:03 PM:

...same reason why I installed 21 penthouse readers on those p35 machines at the 21 in Boise back in 1999 - those basement readers had fits with the jitters caused by that dbl sided belt usage.

-monte

Posted by Brad Miller (Member # 2) on 02-11-2006, 02:32 PM:

For anyone still running P35s with basement readers, I remember back the last time I used them (6 years ago) that if I set it to scan at 102% and threaded with zero tension that they would track quite darned well...and I mean 0-3s all the time. If they were threaded with normal tension, that would jump quickly to 5 at it's best. Consequently, if the reader was scanning at 97-101% it wasn't as good either. Don't know why, but it worked.

(Bear in mind they had to be aligned with zero tension on a very large loop.)