First:
I took a look at the "Waco Glider" BC-230 and traced
the modification they tried for crystal control. It could
never have worked. They tried to make the MO into
some kind of untuned Pierce, with the tunable tank
entirely disconnected so no energy storage,
no clear feedback path, attempting to inductively-
couple via untuned coils to the PA grid and the crystal
from grid directly to ground.
The result was both PA and MO unbiased, drawing
heavy current and blowing-open MO plate dropping
resistor #102. They also bum-fuzzled the bias
development so that, even if the MO were to oscillate,
the PA and Modulators would be unbiased.
There is an easy, completely reversible way to install
crystal control which mimics the crystal coil set, C-184.
if anyone is interested. Before one goes to the effort,
please consider that, given good components,
good grounds and well-regulated B+ and A+ supplies,
the little transmitter is quite stable and, when keyed
as-designed with a B+ relay, nearly chirp-free.
https://drive.google.com/drive/folders/1gYyA-V6Lw-JLk-Umy4puroYzKWiHaZys
This hacked transmitter is going to need extra time
and attention to fix all this.
I'd dedicate it to "Hanger Queen" parts service,
were it not for that tail number. In the mean time,
we can still use it for tips and illustrations.
Most of you "know the drill" when it comes to
the preliminary steps to any radio resurrection;
If it's dirty, clean it. If it's mechanical and moves,
oil it. If it's electrical contact and moves, De-Ox-It.
Go from one end of the rig to the other, checking and
tweeking every ground point. Hi-Z grounds in our
goodies are becoming just as common as bad caps.
This can be a challenge:
Some of these neat little transmitters are within
shouting distance of 100 years old. Many of the
connector contacts are "riveted" or pressed together.
Over the years, the metal in the rear connector pins
and the coil set posts can fatigue and fracture.
Check each one of these connections. If one is loose as above,
one must carefully move the wires in the way and use a large
iron to solder it back into place. Yes; it's tedious, but
"your patience will be rewarded."
Replacing capacitors:
I do not attempt to re-stuff the original caps. For one thing-
doing so destroys their original composition. For another:
I'm lazy. I cut the wires at the caps, cover the end of it
with heat shrink, leaving the wire in place, then trace it to
its connection point. There's always a way to connect the
replacement from that point to ground or where ever needed.
.1 uFd caps at 400VDC are available half the size of a postage
stamp.
