Bob,
I believe that the driver and PA bias voltage should be set to about .70
volts not .07 volts. That could just be a typo from Paul at Ten Tec.
Not sure about what the total current to the PA board should be but that
seems like a better way of setting bias as the voltage would just be a ball
park figure.
Are you sure about the 30 mA and 140 mA values???? If you have access to
a clamp-on mA meter you would not even need to unsolder the power lead to
the PA board.
Thanks and 73, Bill - K6WLM
----- Original Message -----
From: "Bwana Bob" <wb2vuf@verizon.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Cc: "carlos popelier" <carlos.on6cn@gmail.com>
Sent: Saturday, January 29, 2011 10:51 AM
Subject: Re: [TenTec] century 22 setup driver and pa
> Carlos:
>
> To read the current, you can unsolder the red +12 V lead to the driver
> and final board and insert a milliammeter in series with it. This will
> give you total current into the board. I don't know if the 30 mA and
> 140 mA settings refer to total current or collector current, so this
> would affect the procedure, which I don't have. If it's total current,
> you set the current into the board to 30 mA, then go key down with no
> drive and set the current to 140 mA. If the values represent collector
> current, you will have to set the driver bias to min, read the current
> into the board and adjust the driver bias for an increase of 30 mA, then
> go key down and adjust the final bias to increase the current by 140
> mA. I'm looking at the manual for my Corsair, which used the same
> driver transistors (MRF-475) as the Century 22. The Corsair manual says
> to set the driver bias to 4 to 8 mA, so the 30 mA must refer to total
> current into the board. After I replaced my C-22 finals, the total
> current into the board was 159 mA, which I reset to 140 mA TOTAL.
>
> I wasn't sure about this procedure, so last week I contacted the factory
> by e-mail, asking how to set the biases and Paul Clinton replied and
> said that I should set the base voltage on the drivers to 0.07 volts,
> then with the drive at zero, lock the radio into transmit and set the
> final bias voltage to 0.07 volts. There is a test point pin next to the
> base of each transistor. Here is the text of his e-mail:
>
> "With the 579 in receive mode set the base voltage of the driver
> transistors 0.07 volts DC using a digital voltmeter. Place the 579 in
> LOCK with no drive and adjust the base voltage of the final transistors
> to 0.07 volts DC."
>
> This is a very much different procedure. My guess is that the C-22
> driver and final were originally set up for class AB linear operation
> and Ten-Tec later changed it to class C, since CW transmitters can run
> OK in class C. Maybe someone else has some insight into this. I haven't
> tried the 0.07 volt settings yet. My C22 is presently on the bench with
> a possible intermittent short that causes excessive current drain in the
> final. I'm still working on it, but will let you know when I get it
> back on test.
>
> By the way, Ten-Tec replaced the original drivers and finals with type
> 2SC1969.
>
> 73,
>
> Bob WB2VUF
>
>
>
>
>
>
> On 1/28/2011 4:08 PM, carlos popelier wrote:
>> hello,
>> current settings for driver and pa by tentec are 30 mA and 140 mA,
>> this is done by setup driver and pa potentiometers,
>> question: how can i measure this current values and the best way to do
>> it,
>> or the entire setup procedure.
>> thanks carlos
>>
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