|This is a little battery broadcast set using two # 30 tubes. The first tube acts as a regenerative detector with a variable coupling feedback coil. The second tube is an audio amplifier driving headphones.|
|Again, I used solid Mahogany for
the base and front panel with no stain, just the natural wood showing
through the several coats of lacquer. I wanted to add a personal
touch to the panel so I made two cutouts of a hummingbird in the upper
corners. The left knob adjusts the regeneration and the right
knob adjusts the filament voltage.
|As you can see, the circuit is
very simple. The B+ is 22 to 45 volts and the A+ is two "D" cells
in series. You sometimes see this circuit with the "A" supply
reversed. I couldn't tell any difference in operation. The
transformer is an All-American 5 to 1 ratio which helps with the
over-all gain. The headphones are vintage 2000 ohm.
|Back view showing the nice globe shaped
# 30's and the vintage binding posts with markings.
|Left side view showing the coil
assembly. It was in bad shape when I acquired it. I had to
completely replace the green silk wire on all three windings.
Also, notice the variable capacitor. It is another NOS AMSCO
straight line frequency unit from my collection.
|Top view showing the transformer and
filament rheostat. You can't see much of the wiring, but I used #
16 solid tinned wire with black lacquered cloth spaghetti tubing I
purchased from Antique