[Boatanchors] Gonset 972A

[rayfri]

Found a couple comments online about the 4X150a ... Apparently one might 
expect 250 to 300 watts output (500 PEP) with an AC supply... SO, does 
this mean that I should cut my two meter driving power down to about 
half a watt? Doesnt look like I should
be punching this thing with 30 watts of FM power....
Ray

Push Pull Class AB2 Amplifier
Plate Voltage ................................. 1250 V
Grid No. 2 Voltage ............................ 300 V
Grid No. 1 Voltage ............................ -44 V
Peak Grid No. 1 Voltage........................ 100 V
Plate Current ................................. 475 mA
Grid No. 2 Current (Zero Signal) .............. 0 mA
Grid No. 2 Current (Maximum Signal) ........... 65 mA
Driving Power ................................. 0.15 W
Load Resistance ............................... 5.6K ?
Power Output (approx) ......................... 425 W

A 4x150A-4CX250B-4CX250R family tube will actually put out 500W PEP 
okay, if used at maximum plate voltage in a high-efficiency circuit. The 
old rule about power tubes, where output power is generally 2x the plate 
dissipation rating, holds up pretty well. 2x 250W = 500W. The problems 
with this tube are:

-Doesn't work well in grounded grid, so grid and screen supplies, in 
addition to a HV supply for the plate, really are required. This 
complicates power supply design and construction.

-They have enormous power gain, so with a tuned input it's easy to run 
"full power" (e.g., 500W PEP output) with only 3-4W of drive. 15W would 
be *waaay* too much, in many cases. You only need about 55v peak grid 
voltage to drive this class tube to the limit, and with a tuned grid 
input network, it's easy to hit that with only a couple of Watts of 
drive. Thus, it's really easy to overdrive this tube -- and destroy it 
in the process.

-They have a really puny grid and screen dissipation rating, so without 
a lot of prevention circuitry it really is easy to destroy by small 
cockpit errors. On the other hand, I have homebrew 4CX250B amplifiers I 
built in the 1970s which have thousands of hours of use on them and 
still have the original tubes, running fine. It's a matter of monitoring 
grid and screen currents and knowing how to control them.


Glen Zook wrote:

>It uses the 4X150A and operates primarily in AB-2.  It
>was made for mobile operation and has a 12 VDC
>built-in power supply.  According to my references it
>puts out about 90 watts peak on SSB and 120 watts on
>CW / FM.  SSB drive power is about 5 watts and CW / FM
>is 30 watts.
>
>Original cost was $299.00 and there was an
>installation kit that had a control head, cables,
>etc., that cost $59.00.
>
>Glen, K9STH
>
>
>--- rayfri <rayfri at highstream.net> wrote:
>
>Turns out it is not a 903 or 903A, but a Gonset 972A. 
>   Anyone familiar with it?    The ID tag says 144 to
>174 mhz.... 
>
>
>
>
>
>
>
>Glen, K9STH
>
>Web sites
>
>http://home.comcast.net/~k9sth
>http://home.comcast.net/~zcomco
>
>
>	
>		
>__________________________________ 
>Yahoo! for Good - Make a difference this year. 
>http://brand.yahoo.com/cybergivingweek2005/
>_______________________________________________
>Boatanchors mailing list
>Boatanchors at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/boatanchors
>** List Administrator - Duane Fischer, W8DBF/W9WZE **   
>** For Assistance: dfischer at usol.com **         
>$$ For vintage radio info, see the HCI web site $$      
>http://www.w9wze.org    
>
>
>
>  
>