Jim,
I commend you for what you are doing for a nice HB amplifier. I have a
couple suggestions.
I wind my own plate RF and filament chokes. For the plate RF choke I use
fiberglass tubing available from Alan Bond for next to nothing and get # 24
wire from a local electric motor shop. Before I got a small lathe I would
use an electric drill with a piece of 1/4 shaft in it and some rubber feet
on each end of the tubing to hold it and rotate the tubing and wind the wire
on it. For the filament chokes I have used both straight 8 inch rods and
torroid cores and I wind two # 10 wires (also obtained from the electric
motor shop) to form a bifilar choke.
If you are wanting to use the Z-50 choke in the HV lead after the big RF
choke you can wind a smaller choke from the same # 24 wire to fill that
need.
Good Luck,
Terry W6RU
----- Original Message -----
From: "Jim Isbell" <millenniumfalcon@cableone.net>
To: "Mail list for Amplifiers" <amps@contesting.com>
Sent: Wednesday, May 21, 2003 8:31 AM
Subject: [Amps] A new hombrew from old parts
> 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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