I ran (4) 6AG7 tubes with about 1100 or 1200 volts on the plate. They were in
grounded grid and were pressed into a heatsink I made of a block of aluminim. I
had drilled 1"holes in it and using a table saw with carbide tip blade cut
slices to make fins. It required some air blown over the heat sink but it
worked great and no steam.
It only took a few watts to drive and could run continuously at over 150
watts plate input power maybe more.
I have been trying to find the parts for this amp but have only found the
heatsink. I had a large TV transformer mounted with a voltage doubler and used
a pair of large AC run capacitors for the filters.
6L6 tubes are not so good for grounded grid due to the additonal capacitance
between plate and cathode. The beam forming plates are internally connected to
the cathode. I once tried a 6DQ6 ing GG but it was not stable on the higher
frequencies.
I had to condition the tubes by initially bring up the HV lowly and letting
them spark. But after getting them up to the full plate voltage I had no
problem. I'd like to do the experiment again and take some real measurements.
I did open up a tube to see what had happened inside. It had two parallel
plates inside and no glass envelope. I am guessing that there was good black
body radiation to the metal shell that allowed it to work at such high power
for a tube intended to be a video amplifier for early TV and for low power RF
applications such a buffers and oscillators.
73
Bill wa4lav
73
Bill wa4lav
-----Original Message-----
From: "Bob Good" <k4bg@planters.net>
To: <Amps@contesting.com>
Date: Sat, 25 Dec 2004 09:34:27 -0500
Subject: [Amps] Ref: 4- 6AG7 Linear
Nostalgia ! I aquired my CE 10-B in 1960 and ran it barefoot (!) beside my PP
TZ-40's. I knew of some hams who built the 4- 6AG7's but they only ran 1kv to
the plates at 100 ma. Perhaps 6L6's would run a bit more. Now if you only
could turn them upside down into a coffee can filled with water like we used to
do with the AT-1 ! ( metal tubes required ofcourse.) Thanks for the memories.
Seasons Greetings.... Bob K4BG
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