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The Collins C100A Tube
Small Gridless Osc. tube, long T9 bulb on 6-pin base, two mesh electrostatic control elements outside bulb,
six parallel wires a cathode, twin tubular anodes. Xtal osc. in 1935-37 Collins xmtrs.; made by AX.
Some are stamped "Amperex" instead of "Collins" ref. Tube Lore
Collins was being threatened with a law suite from The Radio Trust collectively know as the RCA, ATT,
Westinghouse, over Collins use of certain circuits whom the trust owned the patents on which were purchased form Deforest.
Also at issue, was the Deforest Triode Oscillator. As a workaround for the critical oscillator patent was for Art Collins to
Secure the patent rights from Dr. Robert Goddard of Liquid Fuel Rockt Fame who had obtained a patent on his unusual external
grid vacuum tube in 1915. Collins developed its own oscillator circuit around this unique tube having its grids on the
outside of its glass envelope. Produced by Amperex and branded the C100A, this tube was somewhat quarky in its
operation and required compontent tweaks to ensure reliable operation. Today, the C100 series tubes are among the rarest
of the collectible Collins tubes. The C100A and C100D were the only production versions of this unusual tube with the
B, C, and E being prototypes.
In the 30FXC, the C100A drove a single 46 frequency multiplier or a second cascaded 46 multiplier depending upon
desired operating frequency.
Reference: Gary Halverson video "The Lost Decade" can be viewed on Youtube or our VIDEOS page.