[AMRadio] Questions on Johnson Ranger II

[ne1s at securespeed.us]

> Geoff, and others...
> OK, upon some checking I find the R35 Modulator screen voltage adj
> resistor to be open between where the wiper is attached and to  ground.
> (close to the ground side).
> There is about 9k between the wiper and the big 10uf cap.
> Would this cause the modulator current to read 100ma??

Yes, it will cause the modulator tubes to idle at a higher current because
the modulator screen voltage will be higher. The wirewound resistor with
the slider is a voltage divider, and the "bottom" resistor of the divider
is no longer present.

If you can't find a suitable replacement, I might feed the modulator
screens from the low-voltage B+ (around 300V) and make the control grid
bias adjustable to set the idle point.

I think you had asked earlier about PTT. The Johnson retrofit PTT circuit
is OK with one exception: it doesn't disable the modulators in standby.
You can add a 2nd relay, or a 3rd set of contacts, to either open up the
modulator cathode circuit in standby, or switch the modulator screen grids
from ground (standby) to the screen voltage source (transmit).

73,
-Larry/NE1S