[Collins] kwm-2 fan and outputs

[Dr. Gerald N. Johnson]

On 10/11/2010 12:25 PM, Glen Zook wrote:
> No!  What I was saying that in some transmitters, NOT the Collins
> S-Line and KWM-2- series, that the neutralization can drift.  In well
> over 90% of the Collins equipment the ceramic trimmer will very
> rapidly become "toast" if the 6146B/8298A is used!

Ah so. Too much circulating current in the trimmer.
>
> As for the reason for the 6146A/8298:  Art Collins probably had some
> input as to the design change.  However, the primary reason for the
> development of the 6146A/8298 was the incorporation of the "dark
> heater" for use in commercial FM mobile two-way radios.  The "dark
> heater" allows the voltage to drop as low as 5.0 volts (from the
> "nominal" 6.3 volts) and still insure at least 90&  output power.
> The "dark heater" also allows voltages up to 7.5 volts which allows
> for the same range of output power.
>
> There is a notation on the specification sheet for the 6146A/8298
> dated May 1963 that states:  "Controlled zero-bias plate current is
> offered in the 6146A to insure more dependable performance as a Class
> AB-1 linear rf amplifier for single-sideband suppressed-carrier
> service."

Perfect, matches Warren's story. Likely Art wasn't in on the call, with 
probably 10,000 employees and with Art disliking RCA because they gave 
him much guff over patents in the 30s. So this would make 6146A more 
desirable than 6146 for Collins rigs.
>
> As for the Electronic Tube Company 6146W tubes:  Those tubes are
> infamous in the fact that they usually won't even work on 80-meters!
> From what I understand, the company produced like 10,000 6146W tubes
> and got paid for them.  However, before any of the tubes started to
> be used, the company went out of business and the owners
> "disappeared"!

Probably a division of the Electronic Transistor Company of the same 
era. I remember playing with a DC-DC converter for running a 12 volt 
radio in a 6 volt VW and their 2N3055 fried in the transistor curve 
tracer at less than half "rated" current.

The visible plate structure of the ETC 6146 sure was a lot different 
from the RCA plate. Maybe it only had a heater for light and the plate 
with the rest of the tube missing. The pair I tried didn't work at RF, I 
thought they might work for magnetic deflection of a LF CRT display, but 
I never needed the display so I never checked to see if I could make it 
work.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.