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[Amps] A new hombrew from old parts

To: <amps@contesting.com>
Subject: [Amps] A new hombrew from old parts
From: millenniumfalcon at cableone.net (Jim Isbell)
Date: Thu May 22 09:49:16 2003
Where I am:

I am just about through collecting parts for my "new" 4-1000A linear. 
 All the parts have been collected from various "junk boxes" and have 
been previously used...except the tube itself which is new.

What I am doing:

I will be building a "new" amp from parts that were not originally 
designed particularly to be used together so there will be differences 
in the values and I will have to tweak it all into compliance.  I am 
using the schematic from the Eimac publication AS-10 "Zero Bias Triode 
Operation in a 1-Kw Linear" by Larry Kleber, K9LKA as my starting point 
and then tweaking it as need be to make it work with the components I 
have on hand.  One major change will be the input tank that in the 
schematic has a variable capacitor and switched inductor where the tank 
circuit I have on hand has 5 separate coils with caps across and tuned 
by slugs.

What I have:

I have an antenna capacitor ( Johnson 153-30) a plate capacitor (Johnson 
154-15 20-145) a Pi coil (Air Dux PI #195-2) as well as the Eimac 
socket, chimney, anode cooler and tube.  I also received a bypassed 
plate choke and a pair of door knob caps.  Most of the components were 
previously used with a pair of 3-500s in a Kilowatt amp so should suit 
the 4-1000 satisfactorily.  I am not sure about the suitability of the 
plate choke, but the description of the plate choke in the article is 
very close to what I have.  I dont have a grid dipper so all inductance 
will have to be calculated from coil dimensions rather than "dipped". 
 So I am looking for a good formula that will do that calculation for 
round as well as flat conductors.

What I need:

The pieces I still need are the HV power supply (transformer, rectifier, 
and various components), about a dozen .01x1000v ceramic disk caps, a 
few RF chokes (B&W 800, Ohmite Z-50, B&W FC30A), four meters, and I need 
a chassis/enclosure.  For a chassis enclosure I would like to find 
something that would look good with a Collins S-Line.

I would also like to find at least one other schematic so if I decide 
this one is not the best I have some choices.

I would like to know if there is a good description of the initial 
tuning of a "one off" amp since I am sure it will not work right off the 
dock and I will probably have to do some design changes and 
modifications to get it going.  This is my first amp project and I will 
need to know how I can tell if it is working or not working properly and 
some hints on things to try/check/fix when it isn't.  Hopefully someone 
has written up a generic article on "home-brew" amp tuning.

Any help that anyone can offer even just moral support would be appreciated.

Jim W5JAI, near Corpus Christi TX

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