[Amps] Gonset Amplifier
Bill L. Fuqua
wlfuqu00@uky.edu
Wed, 18 Sep 2002 21:28:41 -0400
indeed no 807's had separate leads to the cathode and supressor grid.
I had played with both 1625s and 837s in my younger years. I put the 1625s in an oven to melt the glue holding the base and then unsoldered them. The 1625s did provide more output. I also used 6AG7s, four in parallel grounded grid. I had made a heat sink from a block of aluminum and drilled holds to press fit the 6AG7 into it. My father had a carbide blade for his table saw which I used to cut fins in the block for forced air cooling. At about 1100 volts I ran about 300 watts DC plate input power with a watt or two drive. My electronics instructor was really impressed.
The tubes had to be conditioned by slowly increasing the plate voltage until they arced. Then dropping the voltage and start over again full plate volatge was achieved.
I still have parts of that amplifier. I may reconstruct it sometime just to measure its real performance, Those days most did not have a means to measure output power.
73
Bill wa4lav
-----Original Message-----
From: Gary Schafer <garyschafer@attbi.com>
To: wl fuqua <wlfuqu00@uky.edu>
Date: Wed, 18 Sep 2002 18:28:37 -0400
Subject: Re: [Amps] Gonset Amplifier
The schematic of the P&H is in the CQ SSB handbook. 1959 I think the handbook came
out.
Not much too it. Used the roller coil from a command transmitter. The plate tuning
cap was from, I think, a bc375 tuning unit. The cabinet was the same as the 20A.
Cathodes grounded through an rf choke and driven direct from the exciter. All other
grids directly grounded. That was it!
You could also use 837s in place of the 1625s without modification. The tube manual
rated them at less power but the construction looked exactly like the 1625 and they
would run about the same power as the 1625.
None of the 807s had a suppresser lead coming out of the glass so they could not be
used in GG.
I home brewed several amps in the early 60s with modified 1625s. I always cut a
slot in the tube base to separate the suppresser from the cathode. It was tricky to
do as the two leads were wrapped together a couple of turns. Only certain brands of
tubes could be modified. None of the RCA tubes brought the suppresser lead out
separately. It was connected to the cathode inside the glass envelope. The National
Union tubes were always able to be modified so I would always try to get them when
ordering from Fair Radio.
The 20A barley had enough drive on the low frequencies for those amps On the higher
bands it was worse yet. With 1200 volts on the plates of 4 tubes you did good to
get much over 120 watts out. With more drive they would run a lot more. I have run
them to as much as 800 watts pep input. But tune up time had to be very short and
you could not talk too long! Four 6AG7s in GG for a driver worked well.
I still have a 20A and a pair of 1625s, but now I drive the grids. Much easier to
make power.
73
Gary K4FMX
wl fuqua wrote:
> P&H's amplifier used modified 1625's. Suppressor ( or beam forming plates)
> grid brought out separately from the cathode to reduce input to output
> capacitance in GG operation. This required either removing the base or
> carefully drilling a hole on the side of the base and unsoldering the two
> wires going to the cathode pin, pulling out the suppressor wire and putting
> it into a spare pin.
> The plate voltage is similar to that used in 811A amplifiers so it
> is possible that someone replaced the sockets in a Gonset and put in
> modified 1625's with an filament transformer. An Central Electronics 20A
> will drive the P&H LA400 very well. In fact the two are about the same size
> and color. They almost look like they are made for each other.
>
> 73
> Bill wa4lav
>
> At 04:44 PM 9/18/02 -0400, Mike Sawyer wrote:
> >Hmmmm,
> > I seem to remember that P&H made a '500 watt' (input) amp that used
> > highly cheap and plentiful 1625's. If memory serves me, it was a direct
> > copy from an article out of QST. There was one slight modification. You
> > had to either tie or un-tie the screen from the cathode(?). I've seen the
> > article but it would mean rooting through a stack of slightly moldy QST's ;>)
> >Mike(y)
> >W3SLK
> >----- Original Message -----
> >From: "Steve Katz" <stevek@jmr.com>
> >To: <K6KWQ@aol.com>
> >Cc: <amps@contesting.com>
> >Sent: Wednesday, September 18, 2002 4:06 PM
> >Subject: RE: [Amps] Gonset Amplifier
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: K6KWQ@aol.com [SMTP:K6KWQ@aol.com]
> > > Sent: Wednesday, September 18, 2002 1:10 PM
> > > To: Steve Katz
> > > Cc: amps@contesting.com
> > > Subject: Re: [Amps] Gonset Amplifier
> > >
> > > Yes they did make one with 4 ea 807's
> > >
> >[Steve Katz] No sweat. I've never seen that one, it is probably
> >even older than the GSB-200, I'd guess. 4 x 807 = about 400Wdc input,
> >though, or maybe 200W output power. Doesn't seem worthwhile for a 100W
> >exciter...maybe if somebody has a QRP station it might help. But I'd bet
> >this item would be worth much more in "collector's" value if mated with
> >whatever exciter it was intended to go with, to make a station... -WB2WIK/6
> >
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