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.
Here is the look from this linear. I hat a Drake antenna tuner in this time, so I made the Drake look 🙂
The under side from this linear
In input circuit of the GI7B tube
The net filter on the 220V side
A complete overview
The tube was in a cooling case. The PI-Filter hat two switchable coils, because the roller induct-or was to small.
The power supply side with near 2000 Volt
The bias circurit
With this linear you can make 350-400 Watts on SSB.
Here you can download the schematics from the RF part: HF Teil.sch
Here you can download the schematics from the power supply: Netzteil.sch
Here is the schematics for the bias control
I sold this linear, after a longer usage.
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
Correction to Plate cap and Loading cap positions:
40 Meter
Plate cap 8
Loading cap 0
————————————–
20 Meter
Plate cap 5
Loading cap 2
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
Hello sir,how high is your bias voltage ?
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.
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
Hi Donald!
I have 2m PA with GI7BT, and have big noise from fan (120×120 mm ETRI 125XF 220V 15W) so I replace it with 12V PWM 7W regulated fan.
What kind of fan (? W and m3/h air flow) are you using for GI7B?
Boris 9a3tn