Philco Model 90 Baby Grand (Type 2) Radio (1931)
The Philco model 90 Baby Grand, introduced in June of 1931,
continued the line of successful Philco compacts that had begun
with the model 20 Baby Grand almost a year earlier, in August
of 1930. Its robust, no-nonsense but classical demeanor has
made it today one of the most famous and widely recognizable
of all vintage radios. The original list price was $69.50 with
tubes.
The cabinet design, patented in February of 1931 by Edward L.
Combs, was shared with several other Baby Grands, including
the models 21 and 70. However, the 90's cabinet is the largest
of them all and is immediately distinguishable because of its
sculpted base moulding, compared with the continuous mould-
ing of the other models.
The model 90 uses Philco's 9-tube Balanced Superheterodyne
chassis, which was in the middle of their 7, 9 & 11-tube chassis
line introduced for 1931/32. This same chassis served for both
the model 90 lowboy & highboy.
There was an evolution of the 90's chassis through its year of
manufacture (June 1931 to June 1932). At the time of its intro-
duction the circuit used push-pull 45s in the output stage and
provided no AVC. However, by the early fall of 1931, Philco had
revised the design to provide AVC, based on their "multiplex
detector"* circuit. This required an extra tube and so the push-
pull output stage was reconfigured to be single-ended, using
one of the new type 47 power pentode tubes, in order to keep
continued the line of successful Philco compacts that had begun
with the model 20 Baby Grand almost a year earlier, in August
of 1930. Its robust, no-nonsense but classical demeanor has
made it today one of the most famous and widely recognizable
of all vintage radios. The original list price was $69.50 with
tubes.
The cabinet design, patented in February of 1931 by Edward L.
Combs, was shared with several other Baby Grands, including
the models 21 and 70. However, the 90's cabinet is the largest
of them all and is immediately distinguishable because of its
sculpted base moulding, compared with the continuous mould-
ing of the other models.
The model 90 uses Philco's 9-tube Balanced Superheterodyne
chassis, which was in the middle of their 7, 9 & 11-tube chassis
line introduced for 1931/32. This same chassis served for both
the model 90 lowboy & highboy.
There was an evolution of the 90's chassis through its year of
manufacture (June 1931 to June 1932). At the time of its intro-
duction the circuit used push-pull 45s in the output stage and
provided no AVC. However, by the early fall of 1931, Philco had
revised the design to provide AVC, based on their "multiplex
detector"* circuit. This required an extra tube and so the push-
pull output stage was reconfigured to be single-ended, using
one of the new type 47 power pentode tubes, in order to keep
Philco 90 ...the aristocrat of all small radios.
the tube count at 9. The final chassis design, introduced some-
time in early 1932, combined the LO & mixer stages into one
using the autodyne arrangement (just as for the type II model 70), freeing up one tube and allowing the single-ended 47 output stage to be
upgraded to use push-pull 47s. At the same time, operation of the AVC was improved by adopting the latest type 35 variable mu tubes. Of
these three Baby Grand variants, the second is by far the most commonly found today. The first version turns up from time-to-time, but I
have yet to even hear of the existence of a surviving example of the final configuration**.
The chassis in my model 90 is the second version, employing a single type 47 tube. The complete tube line-up is 24 (RF), 24 (mixer), 27
(LO), 24 (IF), 27 (detector rectifier), 27 (detector amplifier), 27 (1st AF/driver), 47 (output pentode) and 80 (rectifier). The radio covers the
standard broadcast band from 550-1500kc, uses a 4-point tone control ("brilliant", "bright", "mellow" "deep") and provides automatic volume
control. The schematic may be found here.
* For a description of the Philco "multiplex detector" see the bottom of my Philco 111 page.
** Of course, no sooner had I written this than did a 90B with dual 47s turn up on Ebay. Thanks to Chris Wells of PARS for his communications regarding this version of the 90B as well as
the other models in the series.
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