Philco Model 51 Baby Grand (51B) Cathedral Radio (Jan 1932)
The Philco model 51 Baby Grand (51B) was intro-
duced midway through the 1932 season, in Jan of
1932. It was an evolution of the successful 1931
model 50, replacing that model's outdated TRF
screen-grid chassis with a new state-of-the-art
5-tube "balanced superheterodyne" design and
utilizing an upgraded cabinet, offered in "genuine
hand-rubbed mahogany."
Its initial selling price was $39.95 (complete with
tubes) and, considering that the TRF model 50B's
introductory list price was $36.50, it's no wonder
that Philco bragged that the 51B was "one of the
most tremendous values ever offered in radio" and that
"you have never heard of such a price for such a radio".
Other features of the 51 were billed as "super-
heterodyne selectivity....screen-grid power...genuine
electrodynamic speaker...5 Philco balanced tubes,
including new pentode...and Philco Balanced Units
throughout".
According to philcoradio.com, some 23,800 model
51 Baby Grands were manufactured. The 51B's
chassis was also used for the model 551 Colonial
Clock and a Philco 51 Lowboy. Later in the year it
would be placed into the new model 52 tabletop and
console radios too.
duced midway through the 1932 season, in Jan of
1932. It was an evolution of the successful 1931
model 50, replacing that model's outdated TRF
screen-grid chassis with a new state-of-the-art
5-tube "balanced superheterodyne" design and
utilizing an upgraded cabinet, offered in "genuine
hand-rubbed mahogany."
Its initial selling price was $39.95 (complete with
tubes) and, considering that the TRF model 50B's
introductory list price was $36.50, it's no wonder
that Philco bragged that the 51B was "one of the
most tremendous values ever offered in radio" and that
"you have never heard of such a price for such a radio".
Other features of the 51 were billed as "super-
heterodyne selectivity....screen-grid power...genuine
electrodynamic speaker...5 Philco balanced tubes,
including new pentode...and Philco Balanced Units
throughout".
According to philcoradio.com, some 23,800 model
51 Baby Grands were manufactured. The 51B's
chassis was also used for the model 551 Colonial
Clock and a Philco 51 Lowboy. Later in the year it
would be placed into the new model 52 tabletop and
console radios too.
Philco 51B ...one of the most tremendous values ever offered in radio.
The radio covers the standard broadcast band from 550-1500kc and the tube line-up is 24 (mixer & LO), 35 (IF), 24
(detector), 47 (power output), 80 (rectifier). The schematic can be found here, courtesy of NostalgiaAir.
Although the 51B was state of the art for a 5-tube set in 1932, its circuitry did not yet demonstrate the degree of refinement
that later 5-tube superhets would show. The functions of oscillator and mixer had been combined, making use of a self-
oscillating type 24 tube in an arrangement known as the "autodyne", but it would not be until April of 1933 that the much
superior pentagrid-convertor tube would arrive, in the guise of the 2A7 and shortly thereafter the 6A7. Moreover, the model
51's second-detector was based upon plate-detection using a type 24 screen-grid tube, which does not furnish a DC voltage
proportional to the strength of the received carrier, so the set has no AVC. Nevertheless, Philco's 5-tube superheterodyne
circuit was advancing nicely down the path leading to what would later be the AA5 standard. Besides, what was important for
Philco in 1932 was that it did work quite well and proved capable of being successfully mass produced.
(detector), 47 (power output), 80 (rectifier). The schematic can be found here, courtesy of NostalgiaAir.
Although the 51B was state of the art for a 5-tube set in 1932, its circuitry did not yet demonstrate the degree of refinement
that later 5-tube superhets would show. The functions of oscillator and mixer had been combined, making use of a self-
oscillating type 24 tube in an arrangement known as the "autodyne", but it would not be until April of 1933 that the much
superior pentagrid-convertor tube would arrive, in the guise of the 2A7 and shortly thereafter the 6A7. Moreover, the model
51's second-detector was based upon plate-detection using a type 24 screen-grid tube, which does not furnish a DC voltage
proportional to the strength of the received carrier, so the set has no AVC. Nevertheless, Philco's 5-tube superheterodyne
circuit was advancing nicely down the path leading to what would later be the AA5 standard. Besides, what was important for
Philco in 1932 was that it did work quite well and proved capable of being successfully mass produced.
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