[Boatanchors] "Kinescope ", thanks all.

[Richard Knoppow]

----- Original Message ----- 
From: "Sheldon Daitch" <sdaitch at kuw.ibb.gov>
To: <W4AWM at aol.com>
Cc: <boatanchors at mailman.qth.net>; <KO6BB at sbcglobal.net>
Sent: Monday, August 08, 2011 12:42 AM
Subject: Re: [Boatanchors] "Kinescope ", thanks all.


> GE made the color film chain that was at WRDW-TV,
> Augusta, GA, late 1960s timeframe.  The B&W film chain
> was an RCA unit.

     There were a lot of companies who made parts of film 
chains. At KTTV we had General Electric cameras, RCA 35mm 
projectors and Eastman Kodak 16mm projectors plus automatic 
slide projectors, no longer remeber who made those but I 
think it was RCA. I think the "multiplexer" which is the 
moving mirror thing for switching from one projector to 
another, was also made by GE but am not sure. We had seven 
film islands some 35mm only, some 16mm only and some with 
one of each.
     Dage was a major maker of TV equipment as was 
Westinghouse and others. The early film chains used 
Ikonoscope tubes. They were also used in experimental TV 
cameras but were very insensitive requiring set lighting on 
the order of 1000 foot candles. Enough to melt your skin. 
RCA came up with the Image-Orthocon tube about the late 
1940's. This tube had a photo multiplier in it that very 
substantially increased sensitivity. These were used in 
nearly all studio and location cameras. The studio version 
required about 200 ft/c and the location version would make 
good pictures with below 50ft/c. These were delicate tubes, 
temperature sensitive, and you coundn't point a camera 
straight up or down or stuff would fall on the image forming 
matrix. The secondary emission characteristic of the earlier 
IO tubes led to the familiar black halo around bright 
objects in the image. This was actually exagerated by CBS on 
theory that it improved image sharpness. CBS had the worst 
looking pictures on network air. A later version of the IO, 
called the "separate mesh" tube eliminated the secondary 
emission and halo effect. These tubes were used in later B&W 
cameras in the the early color cameras. AFAIK IO tubes were 
never used in film chain cameras. The Ikonoscope had the 
electron gun at an angle to the image plate so required a 
rather complex sweep circuit to correct for the key-stone 
effect and also correct for the shading brought on by the 
varying distance of the gun. These cameras were capable of 
very good quality but were a PITA to get aligned and 
adjusted right. They also used a "bias light" actually four 
No.47 dial lights to overcome a non-linearity in the curve 
to get better reproduction of blacks.
     When you know what was in that stuff its amazing any of 
it worked at all let alone producing pretty good video. NBC 
had the best pictures, CBS the worst. ABC pretty much 
followed NBC and RCA recommended operation so also had good 
images. DuMont, while they existed, of course used DuMont 
equipment. Capable of pretty good pictures. WWJ, in Detroit, 
where I grew up, used all DuMont equipment (and Western 
Electric at the radio station) because the CE hated RCA. I 
remember seeing a live audience show there with the DuMont 
cameras that looked like travel cases. The got dis-assembled 
immediately the program left the air. FWIW, DuMont used 
composite synch to the cameras rather than separated drive 
and synch as RCA did.
     BTW all this equipment was very much boatanchor. An RCA 
TK-11 with monitor weighed about 100 lbs.
     I am amazed that anyone is still interested in this 
stuff.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com