Philco Model 90 Baby Grand Cathedral 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, complete
with tubes (though some stores charged more - see ad below!).
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 the
vaulted mouldings around its base, compared with continuous
mouldings on each 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, sometime in the fall of 1931 Philco
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
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 out-
put 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, though the third version, with
dual 47s, seems particularly rare.
I have both first and second versions of the model 90 (the set
photographed is the first). The first version has tube line-up
24 (RF), 24 (mixer), 27 (LO), 24 (IF), 24 (2nd detector), 27 (1st
AF), 2 * 45 (push-pull power amp) & 80 (rectifier). The type II set
has the line-up 24 (RF), 24 (mixer), 27 (LO), 24 (IF), 27 (det-
ector rectifier), 27 (detector amplifier), 27 (1st AF/driver), 47
(output pentode) & 80 (rectifier). The radio covers the standard
broadcast band from 550-1500kc and uses a 4-point tone cont-
rol ("brilliant", "bright", "mellow" "deep"). The type II (and III) sets
provide automatic volume control. The schematics may be
found here for all versions, courtesy of NostalgiaAir.
Philco 90 ...the aristocrat of all small radios.
|"If, with a PHILCO, you can't
get the station you want, it just
isn't on the air, that's all"
|"9-tube Superheterodyne... 4 Screen-Grid Tubes...
Pentode Extra Power Tube... Automatic-Volume-Control...
Extra Large Size Dynamic Speaker... Full-Range Tone
Control... Lighted Dial. A Super-Powerful Baby Grand with
a pleasing tone"
1st version model 90 ad
- July 1931
* For a description of the Philco "multiplex detector" see the foot of my
Philco 111 page.
2nd version model 90 ad
- Nov 6th 1931