with A. C. Radiotrons and gives a smooth control of volume without distortion.
4. No neutralizing condensers are employed. Grid resistances in the two tuned radio frequency stages
effectively prevent any tendency to self oscillation.
5. Raw A. C. of the correct voltage is used for filament heating of all Radiotrons. This eliminates the
use of "A" batteries.
6. The three B. F. stages and the first audio stage receive a plate voltage of 135 volts in conjunction
with a negative grid bias of 9 volts. The detector receives 45 volts plate supply without grid bias. The last
audio stage receives
a,
plate supply sufficient to provide ample loudspeaker output. The plate and grid
voltages are supplied by means of a built-in " B " and " C " supply using Radiotron UX-280 as the
rectifying device.
7. Radiotron UX-171 in the last audio stage provides ample volume without distortion in loudspeaker
reproduction.
Figure 4A
—Schematic circuit diagram of socket power unit.
The various circuit characteristics of Radiola 17 provide for easy installation and simple operation
coupled with quality reproduction delivered
to
the loudspeaker.
(3) RADIOTRONS
Radiotrons UX-226 are used in all radio frequency amplifying stages and in the first audio
amplifying stage. It has an oxide coated filament consuming 1.05 amperes at 1.5 volts.
Radiotron TJY-227 is used for the detector.
It operates on raw A.
C. for filament supply, making
use of an indirectly heated cathode. This Radiotron has five prongs, the extra prong being connected to
the oxide coated cathode. Under normal conditions Radiotron UY-227 should give little trouble.
However, in some cases a slight howl may develop in the detector circuit which will necessitate
substituting another UY-227 Radiotron. Although a howl may develop in a receiver with one UY-227,
in another the same tube may prove 0. K. On examining a Radiotron UY-227 in operation, a slight
flickering of the heater
7
