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Author Topic: Converting Sweep Tube Amplifiers  (Read 5086 times)
KO4NR
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Posts: 117




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« on: July 04, 2003, 09:38:48 AM »

Got a sweep tube amp gathering dust in a dark corner of the shack?  Dig it out and convert it to a GI7B or GI7BT Russian Metal Ceramic tube.  These tubes are Triodes and do not require expensive sockets.  Just clamp the grid to the amp's chassis and connect the heater/cathode.  Filament voltage and current requirements are 12.6 volts at about 3 amps.

Thede tubes are inexpensive and one will do as much power out as four 6LQ6 tubes.  The amp's orginial power supply can be rebuilt very easily as a voltage doubler.  

Check my web site for details:
http://www.geocities.com/ko4nrbs

73,
Bill
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W7DJM
Member

Posts: 1




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« Reply #1 on: July 06, 2003, 04:30:06 PM »

Well, the only problem is, you'll probably have to rebuild the plate circuit, as well.  First, if you raise (at least double) the plate voltage, the cap ratings in the entire output circuit may be a little small.

Not only that, but any of these low voltage, multi-tube sweepers have a very low output impedance--so you'll likely have to change the plate tank values, too.
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KO4NR
Member

Posts: 117




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« Reply #2 on: July 14, 2003, 10:12:26 AM »

Dentron GLA-1000 and GLA-1000B tube conversion to a single GI7B information here:
http://www.nd2x.net/w4emf-GLA.html

73,
Bill
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W9GB
Member

Posts: 2579




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« Reply #3 on: July 20, 2003, 12:24:30 AM »

Bill while this is true, some of the surplus Russian tubes being purchased have failed -- since these tubes have been sitting on Russian shelves for over a decade.  Here is a web page anyone buying surplus russian tubes!
http://www.nd2x.net/tube-prep.html

Using tubes which have spent a significant amount of time, often years, "on the shelf" awaiting use! Due to the nature of physical materials, a certain amount of gases are always trapped inside the metals and ceramics, etc., used to construct each tube. A vacuum tube depends on a relatively hard vacuum to function without arcs and other undesired, often disasterously destructive, internal current flow. While in storage, a certain amount of the gases trapped in its materials is "leached" out into the vacuum of the tube. If one were to plug such a tube into an amplifier and apply all voltages and drive, the small amount of gas within the tube would ionize and provide said undesired internal conductive paths; such conduction often reduces an otherwise useful tube to trash. It is, however, possible to prevent these events from occurring by taking some rather simple measures to prepare such tubes for use!


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