[Amps] door knob capacitors

[Glen Zook]

I don't really have enough plate voltage on them right now.  Under load ended up with around 1700 volts.  But, that is what I get out of the transformer that I had in the junque box!  The plate current is right at 600 mA which gives an input of about a kW.  The 700 watts output is what I am showing on both my Collins 312B-4 and on my old Swan 1500 watt meters.  Now I realize that the absolute readings do have a tolerance!

When I locate a transformer that can put out a higher voltage under load I need to change it out.  Also, the junque box transformer only has a 120 VAC primary and I definitely like to run my linears from 240 VAC.

I ended up using a W4ZT bias board and adjusted it for an idle of about 100 mA.  I don't have a grid current meter installed so I don't know exactly how much grid current the tubes are pulling.  The input is not tuned and is loaded with a 50 watt 100 ohm thick-film resistor.  I am using an old Hammarlund HX-50A for the exciter and it is rated at 60 watts output.  But, I usually get around 70 to 75 watts out on 160-meters.

I homebrewed the socket and there are a couple of photos at

http://forums.qrz.com/showthread.php?282380-Socket-for-Russian-tubes

Photos of the basic amplifier are at

http://forums.qrz.com/showthread.php?284611-Almost-ready-for-smoke-test

Since I am the Head Moderator on QRZ.com I put the information in the "homebrew" forum on the site.

The idea was to build the amplifier for the lowest cost possible using junque box parts whenever possible.  Fortunately, I do have a pretty well stocked junque box!

Glen, K9STH

Website:  http://k9sth.com


--- On Mon, 2/28/11, Gary Schafer <garyschafer at comcast.net> wrote:

Interested in the parameters on the GI-7B tubes. I have a pair here to put together.
 
What plate voltage do you have on them?
How much plate current?
How much bias?
Plate idle current?
Grid current?
Drive power?
Output you said was 700 watts.