[GreenKeys] Radio valve/tube CG 502A

[Bruce Gentry]

These are electrically equal to the 2050 thyratron, but in metal shells. 
At Midstate Elevator we bought a couple cases of those in the early 80s 
for use in older Otis controllers. They were  cheaper than the 2050, and 
seemed to be more stable. In some controller circuits, the heater 
voltage was carefully regulated so the firing voltage would be constant. 
There are solid state plug in replacements for them today, but they 
false fire too often and RF in the machine room causes lots of troubles. 
Some things are still best done with tubes. There are few techie nerd 
delights like a large relay logic elevator group control system in 
operation, but the number of them still in service is decreasing fast 
today.

      Bruce Gentry

On 3/22/17 1:43 PM, Jones, Douglas W wrote:
> On Mar 22, 2017, at 11:48 AM, E. Groenenberg wrote:
>
>> I have found 10 pieces of radio valves/tubes, metal can with
>> the print 'JAN CG 502A' on them
> Google finds this document title, published Aug. 5, 1955 and currently listed as obsolete with no superseding document:
>
> MIL-E-1/909 › Electron Tube, Transmitting, Thyratron, Tetrode, Gas JAN-502A
>
> Type 502A tubes appear to be widely available at $5 and up.  I didn't find a spec sheet, though.
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