My first selfmade linear with one GI7B

In August 2012 I start with building linear’s. I start at first with one Russian GI7B tube. I finished it in December 2012. I have no pictures any more from the building phase, but I can show you what I have.

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Here is the look from this linear. I hat a Drake antenna tuner in this time, so I made the Drake look πŸ™‚

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The under side from this linear

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In input circuit of the GI7B tube

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The net filter on the 220V side

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AΒ complete overview

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The tube was in a cooling case. The PI-Filter hat two switchable coils, because the roller induct-or was to small.

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The power supply side with near 2000 Volt

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The bias circurit

With this linear you can make 350-400 Watts on SSB.

Here you can download the schematics from the RF part:Β HF Teil.sch

Here you can download the schematics from the power supply:Β Netzteil.sch

bias board W4ZT
Here is the schematicsΒ for the bias control

I sold this linear, after a longer usage.

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6 thoughts on “My first selfmade linear with one GI7B

  1. Hi there I have just purchased a FL2100Z amp,when tuning up the Plate and Load caps I find the loading capacitor is way out i.e=
    40 Meter
    Plate cap 8
    Loading cap 0
    ————————————–
    20 Meter
    Plate cap 5
    Loading cap 2
    Is there any internal trimmer cap I can adjust to bring the loading cap up from 0.
    Michael ZS1RJQ

  2. Correction to Plate cap and Loading cap positions:

    40 Meter
    Plate cap 8
    Loading cap 0
    ————————————–
    20 Meter
    Plate cap 5
    Loading cap 2

  3. Sorry sorry still have it incorrect, here is the correct setting:
    40 Meter
    Plate cap 5
    Loading cap 0
    ————————————–
    20 Meter
    Plate cap 8
    Loading cap 2

    It seems as though the Loading cap needs a bit more uF

    • I can’t say that. I atjust the bias with a unmodulated signal (ptt only), at that value in the milliamp meter, what the datasheet said.

  4. this is simple

    this amplifier is plagued with band switch issues and padder cap issues. depending on the band, the band switch selects additional capacitance (padder caps) that it parallels with the load control, so its working range will be right for the particular band. It is obvious that either a burned contact or a bad padder capacitor is the cause of your load control all the way meshed and still not at peak power out.
    Good luck. Band switches are hard to find, and the new one may, due to bad design, have a parasitic pulse that will destroy your new, expensive band switch or padder caps.
    As the saying goes- Junk it and buy an Alpha!!!!!!!! I have two, and love them. Bruce N4JHY, 73

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