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Stromberg Carlson 350R Half-Round Console Radio (1939)
The Stromberg Carlson 350R is an impressive three
band 11-tube console radio that features a tuned RF
stage, three-way high-fidelity control, Automatic-
Frequency-Control (AFC), concentric coarse/fine
tuning control, magic-eye tuning indicator and
push-pull output stage with the "acoustic labyrinth
speaker" system. Tuning ranges are 530 - 1700kc,
1700 - 5600kc and 5600 - 18,000kc. The tube
line-up is 6K7 (RF amp), 6A8 (mixer), 6F8G (LO &
LO freq control), 6K7 (IF), 6H6 (discriminator/2nd
det/avc), 6B8 (discriminator/1st af), 6C5 (phase
invertor), 6F6 * 2 (push-pull output), 6U5 (tuning
indicator) & 5Z3 (rectifier). Interestingly, the RF amp
is only used with the standard broadcast manual
tuning range. The high-fidelity control, like that on
a number of other contemporaneous receivers, is
achieved, in part, by adjusting the bandwidth of one
of the IF filters. The knobs are, from left to right,
volume, fidelity control  high/normal-tone, tuning,
waveband selection, on/off/bass. The schematic
may be found
here, courtesy of NostalgiaAir.

The AFC serves to lock-in the frequency of the LO to
that of a received broadcast carrier, mitigating the
effects of drift caused by component aging, temp-
erature changes, and so forth. This was especially
helpful when using the electric tuning feature (i.e
push-button tuning). An AFC defeat switch is located
on the rear of the chassis, mainly for usage of the
service technician when aligning the set. Philco
employed the same technique on a number of their
higher end sets, such as the
37-116. They referred
to it as "
magnetic tuning".
Stromberg Carlson Console Radio Model 350R (Doors Open)
Stromberg Carlson Console Radio Model 350R (Doors Closed)
Chassis view, in as found condition (Stromberg Carlson 350R)