Regarding the 4K-U mods, all I did was eliminate ALL of the input circuitry
right up to the blocking cap and replaced it with the LDG auto tuner that
they sell for $129. It has no cabinet and requires a 12VDC supply, which are
found on ebay. I also changed the tube to a 3CX1200D7, eliminated all the
ALC and center tune crap, took out the 2 filament transformers, changed the
Zener on the back to 6.8V and installed a quieter blower. I mounted the new
filament xfmr down in the power supply and made a quick disconnect for the
filaments up in the RF deck. I also had to put in a huskier filament choke
since the 1200D7 draws 25A.
I have pics but none that show the before-after sequence.
Re: the tracking, I really don't think that the 4KU ever tracked well to
begin with. Ted Henry says that they tuned it up for full smoke on 20 and
the other bands took care of themselves. This is what I basically did also.
Since I don't care about 15 and 10 meters, I haven't even checked those
bands. 20, 40 and 75 seem to work fine. Just load it up into a dummy load
on 20, then remove the chain and using a non-conductive stick, tune the
individual sprockets by turning them until you have max out. Put it all
back together and see how it plays. I wouldn't bother adjusting the tuned
input sprockets unless you have high swr showing between the exciter and the
8877.
If you have any other questions, I am just a phone call away. 813-643-3034
73 Bob W6TR
----- Original Message -----
From: "Saad Mahaini" <n5ff@comcast.net>
To: "'Bob Maser'" <bmaser@tampabay.rr.com>
Sent: Saturday, July 15, 2006 12:09 PM
Subject: RE: [Amps] Tetrode Amplifier
Hello Bob, do you plan to publish some details on all you did to the 4K
Ultra, findings, photos, etc? That will be nice
Also, how familiar are you with the stock 4K ultra. I bought one a while
back, and just can't get it to track well, the chain must have been off and
lost sync. Wonder if you have hints on how to get it tracking well.
Finally, do you have surplus parts from the 4K?
73 Saad N5FF
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Bob Maser
Sent: Saturday, July 15, 2006 10:57 AM
To: AMPS
Subject: [Amps] Tetrode Amplifier
Having just about completed my modifications on the Henry 4K-Ultra, I am
looking for another amp project. I have a source for some 4CX300Y tetrodes
and I just bought some sockets for them. I am thinking about finding a
desktop amp that was commercially produced using goofy tetrodes(or triodes),
no longer made, and relatively cheap that I could modify to use the
4CX400's. Any recommendations? The ideal amp would have enough room to
install screen and bias supplies if it were originally a triode amp. I am
thinking NCL-2000. Any out there?
Thanks,
Bob Maser W6TR
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