"Cheap" and "clamp on ammeter" don't come in the same package for DC.
.07 volts on the base of a silicon bipolar transistor won't turn it on,
.7 may turn it on too much. I find nothing in the manual to help.
73, Jerry, K0CQ
On 1/29/2011 8:05 PM, Bill Miner wrote:
> 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"<email@example.com>
> To: "Discussion of Ten-Tec Equipment"<firstname.lastname@example.org>
> Cc: "carlos popelier"<email@example.com>
> Sent: Saturday, January 29, 2011 10:51 AM
> Subject: Re: [TenTec] century 22 setup driver and pa
>> 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
>> Bob WB2VUF
>> On 1/28/2011 4:08 PM, carlos popelier wrote:
>>> 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
>>> or the entire setup procedure.
>>> thanks carlos
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