[ARC5] Request for info - modulator cct using 6AG6 in class "B".

[Dennis DuVall]

 I would substitute a pair of 6L6s and run them AB1. The 6J5 won’t put out enough power to drive a pair of either
6AG6s or 6L6s into class AB2 or class B. 

Dennis D.  W7QHO
Glendale, CA

*****************

> On Sep 17, 2015, at 8:52 PM, Ian Wilson <ianmwilson73 at gmail.com> wrote:
> 
> I wonder whether the 6AG6 was intended for use in Class B -
> perhaps that explains the high current/gm at low grid bias?
> 
> Will look at a few Handbooks tomorrow. I have never looked
> at the modulator circuits in much detail.
> 
> Sibley says the 6AG6 is a scaled-up 6V6. It is an EL33
> equivalent. Introduced in 1938 (so no point looking for circuits
> earlier than that <g>).
> 
> 73, ian K3IMW
> 
> 
> On Thu, Sep 17, 2015 at 7:33 PM, Leslie Smith <vk2bcu at operamail.com> wrote:
> 
>> G'day list readers!
>> 
>> I have been given a modulator.  100% homebrew.  I intend to use it in
>> conjunction with the ARC5 transmitters.  (I don't have an MD-7 etc, and
>> figure I have little chance of getting one.  My luck is obvious.)
>> 
>> I wish to find a circuit for this "thing" - although tracing is quite
>> possible.  Tubes used (from the 'back' end) are 6AG6G, (x2, in push
>> pull) driven by a phase splitting transformer.
>> 
>> Driving the phase-splitting xfmr - a 6J5.  Before that a 9-pin (noval)
>> twin triode.  Almost certainly 12AX7 - but maybe another member from
>> that family.  There is an unmarked 7 pin pentode - that's clear from the
>> standard pin connections.  At the moment I have no idea about the
>> function of the pentode - I don't see the need for that much gain.
>> 
>> If any-one can point me to the circuit of the modulator, I'll be
>> pleased.  The 6AG6G is an uncommon beast.  It's a beam tetrode, base
>> connection similar to the 6V6, 6L6, 6F6 family - but differs in some
>> respects.  I'm surprised by the combination of high heater current -
>> 1.2A- but lower bias voltage -6V, (but only spec's at 250V B+).  The 6L6
>> family specs are shown for higher working voltages.  This makes me
>> suspect that the 6AG6 is acutally capable of more than the spec sheet I
>> have (for the 6AG6).
>> 
>> 
>>       Characteristic      6V6  6L6  6F6  6AG6G
>>       Filament Voltage    all 6.3
>>                current    0.45 0.9  0.7A 1.2A
>>       Plate dissipation   12   20   12   10 Watts
>>               Bias (G1)   -12 -20  -26   -6 volts
>> 
>> Looking at the size of the modulation transformer I'd guess at 12 to 20
>> watts - understand my 'guess' lacks experience.
>> 
>> To re-state:  I'd like to use this modulator.  It was 'rescued' from a
>> sad fate from a SK's gear; it's neatly built and I'd like to keep this
>> working both because it's useful to me - but also because this has been
>> nicely built, and I'd like to keep this working for that reason.  Can
>> anyone point me to a circuit/article.
>> 
>> 
>> 
>> 
>>  73 de Les Smith
>>  vk2bcu at operamail.com
>> 
>> --
>> http://www.fastmail.com - Does exactly what it says on the tin
>> 
>> ______________________________________________________________
>> ARC5 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/arc5
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:ARC5 at mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> 
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html