That gives me an idea. I have a Thunderbolt and if I go to solid state
rectifiers, a capacitive input filter and then wire up the 866A's in
parallel but in series with the filtered output I would still have the
light show and more output. Just have to have higher voltage filter
capacitors and bypass the filter choke.
73
Bill wa4lav
At 09:17 AM 9/1/2004 -0600, John T. M. Lyles wrote:
The 1960 vintage Heathkit Chippewa amplifier model KL1 was a dual 4-400A
amplifier which worked well in class AB1. It was described in Electric
Radio magazine a few years back, with some modifications to improve it. I
believe that there is an online index to ER which you can look up, and
order a back issue. I believe that earlier W6SAI Radio Handbooks (like
21st edition) elaborated on the craft of building tetrode amplifiers.
About that time the 3-500Z was really becoming a favorite, as a grounded
grid zero bias (low bias) class B amplifier. Setting up tetrodes for best
IMD and linear operation requires a bit more care, as you have both a
screen and control grid bias voltage to deal with. Some have found that
grounding the grid and screen for RF (and applying the DC bias to both)
and driving the cathode is a good way to handle a 4-400A. The Johnson
Thunderbolt amplifier had 4-400As but it ran them in AB2 at too low an
anode voltage, leaving it short of output and prone to being overdriven
(causing IMD).
I have a Chippewa that I am going to restore someday, as it got "modified"
by someone. I saw another one that had been converted to grounded grid,
but wasn't interested as it had been too modified from original, and for
that an SB220 or Drake L4 would be adequate. Problem with Chippewas is
that they had a separate huge power supply chassis with 866As and it is
usually missing or burnt up.
73
john
K5PRO
Message: 1
Date: Tue, 31 Aug 2004 18:23:08 +0200
From: "ON5KM" <on5km@planetinternet.be>
Subject: [Amps] search 7527A design
To: <Amps@contesting.com>
Message-ID: <005601c48f76$d160a020$a284efd4@computer>
Content-Type: text/plain; charset="iso-8859-1"
hi ,
who has a link or info to a good stable design using 1 or 2
7527a's (qb4-1100 or 4-400) ??
all info welcome .
tnx on5km stef
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