RCA C73293C Developmental 3 Gun Color Tube
From RCA 1950 brochure
Here is a Popular Science Article an a Popular Mechanics Article about RCA developmental color tubes. Here is a photo of a set with this tube in operation. A similar tube was used in the RCA CPA prototype presently at the museum.
The following information is from Dave Abramson, owner of the only other
There were only under two hundred of those and
they were only let out to prospective licensees for examination or
for engineering sets. It is truly the first modern color picture
It is a variation of the 16" metal shell tubes in the RCA line.
The mask and phosphor assembly was in a separate front piece and
aligned in a sort of light tunnel, then welded to the rear bell.
The weld ridge became the anode connection. RCA went wrong from
This tube was use in the tri-color models 1 and 2 and possibly the
2A. Model 1 was the first RCA demo to the FCC. These tubes were
circa April, 1950 to February, 1952. Models 3 and 3A used a 3-bolt
version. Starting with the 3, they improved the trajectory of the
guide bolts for the shadow mask alignment. The model 4 appears to
be the first of the glass tubes. Most of what I know can be found
in the RCA Color TV submission to the FCC...the "red book"...and in
the second "Proceedings of the IRE" on color television.
Three screws can be seen above and below the screen.
This is the tube in John Folsom's CBS RX-89 prototype, with 3 screws
located around the screen. It is probably the same tube used in the RCA
model 3 receivers.
From RCA's 1952 Annual Report
Courtesy of Bob Dobush