Philco Model 70 Baby Grand Cathedral Radio (1931)
The Philco Model 70 Baby Grand was first offered for
sale in June of 1931, at the same time as its big
brother, the infamous model 90 Baby Grand.
It employed Philco's 7-tube "balanced superhetero-
dyne" chassis, which was the entry level unit in the
companies line of new 7, 9 and 11 tube receivers. As
usual, they tried hard in their advertising to foster the
notion that their sets offered something more than
those of the other manufacturers. This had been a
very successful strategy for them in the past, with the
neutrodyne plus, screen-grid plus and super-
heterodyne plus, and it would prove to be so again
with these new designs. In the advertising for these
models, they proclaimed "At Last! A radio that truly
meets the modern demand for performance, a
superheterodyne receiver PLUS balanced units PLUS
balanced tubes. ... Remember, superheterodyne is not
enough. It takes Philco's BALANCED superheterodyne to
meet the modern demands of crowded broadcasting
conditions".
The model 70, with an initial purchase price of $49.95
complete with tubes, would go on to sell almost
300,000 sets. So successful was the company during
this period, right in the midst of the great depression,
that by most reckoning more than one out of every
two sets sold in the USA was a Philco.
The cabinet used for the models 70 and 90 had first
appeared three months earlier for the model 21.
However, that set was discontinued by June, with the
introduction of the 70 and 90, and had barely been
promoted by the company. As a result it is rarely seen
today. At any rate, the cabinet was designed by
Edward Combs and has gone on to become one of
the most recognizable of all radio designs from the
tube era. A copy of the Combs patent for the cabinet
can be seen here.
The model 70 covers the standard broadcast band
from 550-1500kc and features a "pentode output tube
for extra power, tone control, electro-dynamic speaker and
illuminated station-recording dial". The cabinet was
available with either walnut or mahogany veneer.
Initial production used a tube complement of 24 (RF
amp), 24 (mixer), 27 (LO), 24 (IF amp), 24 (2nd
detector), 47 (audio pentode) and 80 (rectifier). This
set did not use the Philco "multiplex detector"* and as
such did not provide automatic volume control (AVC).
sale in June of 1931, at the same time as its big
brother, the infamous model 90 Baby Grand.
It employed Philco's 7-tube "balanced superhetero-
dyne" chassis, which was the entry level unit in the
companies line of new 7, 9 and 11 tube receivers. As
usual, they tried hard in their advertising to foster the
notion that their sets offered something more than
those of the other manufacturers. This had been a
very successful strategy for them in the past, with the
neutrodyne plus, screen-grid plus and super-
heterodyne plus, and it would prove to be so again
with these new designs. In the advertising for these
models, they proclaimed "At Last! A radio that truly
meets the modern demand for performance, a
superheterodyne receiver PLUS balanced units PLUS
balanced tubes. ... Remember, superheterodyne is not
enough. It takes Philco's BALANCED superheterodyne to
meet the modern demands of crowded broadcasting
conditions".
The model 70, with an initial purchase price of $49.95
complete with tubes, would go on to sell almost
300,000 sets. So successful was the company during
this period, right in the midst of the great depression,
that by most reckoning more than one out of every
two sets sold in the USA was a Philco.
The cabinet used for the models 70 and 90 had first
appeared three months earlier for the model 21.
However, that set was discontinued by June, with the
introduction of the 70 and 90, and had barely been
promoted by the company. As a result it is rarely seen
today. At any rate, the cabinet was designed by
Edward Combs and has gone on to become one of
the most recognizable of all radio designs from the
tube era. A copy of the Combs patent for the cabinet
can be seen here.
The model 70 covers the standard broadcast band
from 550-1500kc and features a "pentode output tube
for extra power, tone control, electro-dynamic speaker and
illuminated station-recording dial". The cabinet was
available with either walnut or mahogany veneer.
Initial production used a tube complement of 24 (RF
amp), 24 (mixer), 27 (LO), 24 (IF amp), 24 (2nd
detector), 47 (audio pentode) and 80 (rectifier). This
set did not use the Philco "multiplex detector"* and as
such did not provide automatic volume control (AVC).
...a superheterodyne receiver PLUS balanced units PLUS balanced tubes.
Later production, above serial number B-22,000, adopted an improved chassis that did feature the "multiplex detector" along with
variable-mu tubes and AVC. The tube-line up for this type II chassis is 35 (RF amp), 24 (mixer/LO), 35 (IF), 27 (rectifier-detector),
35 (1st AF or detector amp), 47 (output pentode) and 80 (rectifier). The mixer and LO, which used separate tubes in the earlier
chassis, were combined into one self-oscillating type 24 (autodyne arrangement ) and the 2nd detector was reconfigured to use a
detector-rectifier and detector-amp in order to provide AVC.
My radio, photographed above, has the earlier version of the chassis, with no AVC. The schematic may be found here.
* For a description of the Philco "multiplex detector" see the bottom of my Philco 111 page.
variable-mu tubes and AVC. The tube-line up for this type II chassis is 35 (RF amp), 24 (mixer/LO), 35 (IF), 27 (rectifier-detector),
35 (1st AF or detector amp), 47 (output pentode) and 80 (rectifier). The mixer and LO, which used separate tubes in the earlier
chassis, were combined into one self-oscillating type 24 (autodyne arrangement ) and the 2nd detector was reconfigured to use a
detector-rectifier and detector-amp in order to provide AVC.
My radio, photographed above, has the earlier version of the chassis, with no AVC. The schematic may be found here.
* For a description of the Philco "multiplex detector" see the bottom of my Philco 111 page.
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