[Milsurplus] BC-9: A Big Road Block

[AKLDGUY .]

Another possibility is that the 6AQ5 is oscillating very much
more vigorously and driving itself to much greater grid current
than the VT1. That would load the tuned circuit heavily, forcing
a frequency downshift. You may need to set the bias pot R4 to
a considerably higher setting, or even change the bias battery
if you don't want to change the bias divider R3 / R4 values.

Those old tubes were nowhere near as sensitive as modern
cathode types.

73 de Neil ZL1ANM


On Sat, Jan 21, 2017 at 4:21 PM, David Stinson <arc5 at ix.netcom.com> wrote:

>
> ----- Original Message ----- From: "AKLDGUY ." <neilb0627 at gmail.com>
> Subject: Re: [Milsurplus] BC-9: A Big Road Block
>
>
> Yes, I understand that the meter would get slammed. Or would it?
>>
>> There was some doubt about the circuit diagram, with the part of it
>> in the vicinity of the key being missing and retrieved from somewhere
>> else.
>>
>
> Thank you for writing, Neil.  The diagram is correct;
> the key bypasses the meter and C5/R5.  R5 limits the
> B+ on the RF tube to about 70 volts on receive.  When
> the key is pressed, R5 is bypassed and full 120V B+
> is applied to the tube.  I'm getting almost exactly 1W output
> using an external tank coil that is link-coupled to the antenna.
> I mis-typed that on transmit, the OSC was shifting higher;
> it is in fact shifting lower by about 15-18 KC.
> I must assume this isn't a problem with a VT-1 since
> these sets remained in service many years and could not
> have functioned like this.
> I intend to go forward with your suggestion of trying
> a 6C4 in this stage.  We'll see how it goes.
>
> 73 Dave AB5S
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20170121/f8598996/attachment.html>