[Boatanchors] Gonset 972A

Tue Jan 3 10:56:00 EST 2006

I once forgot the air.  Solder melting out of 4X150's makes a sizzling sound
when it
drips onto the chassis!  Didn't seem to hurt the tubes tho.  Later versions
of the X150's
appear to use hard solder.  I've not experimented with them.  :-)

73 de Jack - N7OO

----- Original Message ----- 
From: "James M. Walker" <chejmw at acsu.buffalo.edu>
To: "rayfri" <rayfri at highstream.net>; "Glen Zook" <gzook at yahoo.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Monday, January 02, 2006 11:59 PM
Subject: Re: [Boatanchors] Gonset 972A

> Don't forget the air! I run a pair of 4CX250B tubes on 144 on CW with 1500
> VDC
> adjustable, and 300 VDC fixed for the screens from a separate supply,
> and -40 to 55
> VDC on the grids. I try to keep the output down to 400 watts by limiting
the
> drive.
> The drive level is right around 3.5 watts on CW or SSB. In AM mode I run
the
> rig at 1250 VDC plate volts, and modulate the plates, amp is class "C" at
> that time.
>
> I dump a lot of air through the tubes, and maintain a close watch on the
> filament
> voltage to the tubes, recommended is 6.0 VAC at this freq. You can get a
lot
> of good AM out of them that way.
>
> It is also a good idea to have lots of metering to see when things start
> changing as
> the parameters change during long transmissions. I monitor the grids and
> screens as well
> as separate plate meters. The power should be reduced for 4X150A type
tubes.
>
> YMMV
> Jim
> WB2FCN
>
> ----- Original Message ----- 
> From: "rayfri" <rayfri at highstream.net>
> To: "Glen Zook" <gzook at yahoo.com>
> Cc: <boatanchors at mailman.qth.net>
> Sent: Monday, January 02, 2006 8:21 PM
> Subject: Re: [Boatanchors] Gonset 972A
>
>
> > 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
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