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Technical Highlights

Overview: The 38-116XX is a 15-tube all-wave AC superhetero-
dyne having five frequency bands with automatic tuning, an RF
amplifier, a mixer and LO stage with Automatic-Frequency-Cont-
rol (AFC), two stages of IF with variable selectivity control and a
15W High Fidelity audio system with push-pull beam output stage,
cathedral speaker and acoustic clarifiers. It came with either a
code 121 or 125 chassis type, with all but early production using
the code 125 version. The 125 chassis simplified the number of
adjustments required in the front-end and modified the tube line-
up. A rear view of my restored 38-116XX (with its protective back
removed) may be viewed below right.

My set uses the 125 chassis with tube line-up:- 6U7G (RF amp),

6A8G (mixer), 6A8G (LO), 6N7G (reactance tube), 6K7G (1st IF),
6K7G (2nd IF), 6K7G (2nd detector/magnetic tuning amp), 6J5G
(AVC diode), 6J5G * 2 (AFC discriminator), 6R7G (1st audio),
6J5G (single ended driver), 6L6G * 2 (beam outputs) and 5X4G
(rectifier). The 6J5 driver stage is transformer coupled to the
push-pull outputs. The tuning ranges are:-  530 - 1600kc (band
1), 1580 - 4750 (2), 4700 - 7400 (3), 7350 - 11600 (4) & 11500 -
18200 (5). The schematic may be found here.

Automatic Tuning:  The receiver incorporates Philco's  Auto-
matic Tuning dial, first introduced for the 1937 model year. You
are referred to PhilcoRepairBench for details on this dial's usage,
setting up and service. The US patent for this tuning device,
#2248678, was filed on behalf of Philco on Aug 6th 1936 and was
granted on July 8th 1941. It names the inventors as Glaser, Bow-
man and Briggs and makes very interesting, if not somewhat
challenging reading!

Magnetic Tuning: The receiver features an Automatic Freq-
uency Control (AFC) circuit, referred to by Philco as magnetic
tuning. This was primarily added to work in conjunction with the
Automatic Tuning dial mechanism for the purpose of correcting
residual tuning errors. AFC operates by sensing frequency de-
tuning relative to the IF center frequency (470kHz for the 38-
116XX), automatically adjusting the frequency of the LO so as to
drive any tuning errors towards zero. Three of the receiver's tube
complement is devoted to this purpose.

Variable IF Selectivity: The receiver's selectivity is varied at the
listener's discretion using a front-panel control that mechanically
adjusts the coupling between windings in each of the set's first
two IF transformers. This control also links to a potentiometer
used to apply additional high-frequency cut to the output of the
first AF stage as the IF bandwidth is narrowed. At it's widest sett-
ing, the IF bandwidth is such as to permit reproduction of freq-
uencies up to around 7.5kcs. This is around twice the bandwidth
of standard IF filters of the day and in 1938 was considered ad-
equate for high-fidelity reproduction.

Bass Compensation: A three point bass control switch is prov-
ded that is ganged with the on/off switch. A tapped volume control
potentiometer automatically results in an increased bass resp-
onse at low volumes to compensate for audiometric effects.

Automatic Volume Control: The AVC bus on the 116XX is
connected only to the RF and 1st IF stages. The 2nd IF runs with
fixed bias; to have applied AVC to this stage would have increas-
ed audio distortion, especially in the presence of strong signals.
Another aspect of the AVC is that the carrier is sensed from the
primary winding of the final IF transformer, rather than from its
secondary (from whence is obtained the 2nd detector input), as is
more traditional. This necessitated the use of a dedicated AVC
diode but has the advantage of minimizing resistive loading on
the IF transformer's secondary - an expedient found to minimize
audio distortion. I have to confess that the AF from the 2nd det-
ector on this set looks extremely clean when viewed on an osc-
illoscope with a CW modulated waveform applied to the antenna
input - far more so than on most AM radios that I've had the plea-
sure (or otherwise) of servicing.

Philco Foreign Tuning System: This actually covers a number
of aspects concerning the front-end, primarily concerned with
optimizing sensitivity of the set and its ability to tune and separate
stations (foreign or American).

Firstly, the set was designed to accept a
balanced antenna input
from a device such as the Philco High-Efficiency-Aerial-System.
Each band has its own tuned antenna input circuit, switched in
and out by the waveband selector switch for the purposes of
matching receiver to antenna and thereby maximizing the transfer
of signal energy to the receiver. Pick-up of noise from household
wiring is also lessened through the use of this arrangement
(because of the balanced feed between outside antenna and
receiver). A less efficient conventional antenna input is also prov-
ided for temporary use during test, or for use by those not in
possession of a High-Efficiency-Aerial.

A second aspect of the foreign tuning system is the use of split

stators on the tuning condensors. Each of the three gangs on the
condensor is formed in two sections, comprising a larger and a
smaller capacitance element. On the lowest frequency bands the
two sections of each gang are connected in parallel through the
waveband switch, providing a large capacitance for effective tun-
ing at the lower frequencies. On the intermediate bands only the
larger section is used, while on the highest frequency bands only
the smaller section is switched in. This expedient has the highly
beneficial effect of providing a bandspread capability, i.e. of
spreading stations further apart on the dial.

A third aspect is the use of a dial for which almost the entire 360

degrees is marked, in color, with frequencies and the names of
stations. On many other earlier or contemporaneous so-called
All-Wave sets only 180 degrees was used for frequency markings
and usually there were fewer bands to boot with the result that
stations were far more crowded together. No wonder Philco claim-
ed "stations spread six times further apart" in many of their ads for sets
featuring their foreign tuning system.

The above features are further augmented through the use of a

dual speed vernier tuning mechanism. Overall, these Philcos
provide a great feeling of "space" between stations that makes
them a pleasure to use.

High-Fidelity Speaker System: - the 14" electrodynamic loud-
s
peaker used in the 116XX is constructed in two sections made
out of different grades of paper. The inner section is made stiffer
and more amenable to reproducing high frequencies, whereas
the whole works well for the lower frequencies. Additionally, it's
likely that the voice coil was constructed using aluminum wire for
lightness, again out of consideration for high frequency capab-
ility. This was certainly the case on loudspeakers used by some
of Philco's earlier Hi-Fi sets   (e.g. the 201X) and was likely the
case on this model too.

A sound diffuser is embodied into the loudspeaker opening
be-
h
ind the grille cloth for the purpose of diffusing high frequency
energy and lessening beaming. The diffuser (photo mid-right)
comprises a small conical element inserted into the loudspeaker
opening directly in front of the center of the loudspeaker cone - a
hidden feature of the set that most listeners probably never even
realize is there! The five vertical wooden fins in front of the loud-
speaker grille were conceived of as part of the sound diffuser
also, serving more than just a mere cosmetic function and acting
much like the concealed metallic fins in the model 201X. Some
other manufacturers had done the same thing. In addition to the
diffuser, the set of course utilizes Philco's famed "inclined sound-
ing board", which directs the entire sound field slightly up and
away from the floor.

The 38-116X includes three small diameter acoustic clarifiers

(right), designed to absorb energy at the cabinet's resonant freq-
uency and thereby lessen boom, which if unchecked is particul-
arly detrimental to the reproduction of voices. It is interesting to
note that in the first year of their appearance (1936 season), two
different sizes of clarifier were used. The 1936 model 116X used
three clarifiers, one with an 8.75" cone and two with 6.25" cones.
US patent #2059929 (granted 11/03/36; inventor Bobb, L.J.; Assignee
Philco Radio and Television Corp) explains how these three units act
in concert to reduce the primary cabinet resonances occurring
between 70 and 150Hz, the maximum reduction being around
10dB at 95Hz. Later sets, including the 38-116XX, discarded the
larger diameter clarifier and used three 6.25" units. Apparently,
Philco was able to realize the requisite degree of resonance
flattening using just the smaller 6.25" clarifiers.

Note that in none of the sets using acoustic clarifiers is a cabinet

back necessary for correct operation - it is a common misconcep-
tion that these devices will work only if a back is affixed to the
radio. Cabinet resonance is however noted to be greater when
the receiver is placed near to a wall, so the influence of the clar-
ifiers in reducing boom is then the most pronounced. The 38-
116XX was sold with a protective rear cover in place (right), but
this served a protective rather than acoustical function.

Listening Impressions

I recently completed what turned out to be a routine electrical
restoration of this set and have since had the great pleasure of
spending some time listening to it. Although it does not use
tweeters such as in the top-of the line 38-690XX, the sound
quality from this receiver is superb! There is little sense of
boominess in the reproduction and mid-range timbre is close to
that realizable from FM. Sensitivity across all bands is first rate.
Overall an impressive receiver that is a delight to use and listen
to. One of Philco's best!
Philco 38-116XX (38-116) High-Fidelity Console Radio (1938)
Philco presents the radio of tomorrow today!
The Philco model 38-116XX console radio was one of eight "No
Squat, No Stoop, No Squint" sets introduced by Philco in June of
1937 for the 1938 model year. With an initial list price of $200 for
what was truly a feature-packed set, this radio provided great
performance and extremely good value to those who could afford
to buy it. The 38-116XX was upstaged for the 1938 model year
only by Philco's showpiece 38-690XX set.

I initially purchased this set not for its looks but more for its
tech-
nological excellence and because it filled a void in my line-up of
high-end Philcos. However in short order I've come to appreciate
its decidedly machine age styling. It readily evokes fanciful impre-
ssions of a majestic streamliner, forever speeding forth on a one
way journey away from a long lost era. A befitting image for this
set, from the crowning year of radio's "golden age".

There can be no doubt that 1938 was technologically a banner

year for Philco, with their top models representing a pinnacle of
achievement, the culmination of many years of rapid advance-
ment in the state of the radio art. It's no wonder that the 38-116
XX was referred to in many Philco advertisements as "the radio
of tomorrow today".
"For 1938....Philco presents the radio of tomorrow today!
No longer need you squat, stoop or squint to tune a radio!
The minute you see the new 1938 Philco Double-X models,
you'll realize that the Inclined Control Panel makes
stooping to tune in a station as out-of-date as stooping to
crank an automobile!"
Philco made much play on the No Squat, No Stoop, No Squint
theme in its advertising, but, as they were quick to point out,
"there's far more than the inclined control panel to the Philco story for 1938.
In the 1938 Philco 116 Double-X you'll find all the latest Philco develop-
m
ents, everything you could wish for or hope for in a radio". Below is a
collage of extracts from original Philco advertisements describing
the features of the 38-116XX radio.
- Inclined Control Panel - No Squat! No Stoop! No Squint!
enables you to tune with ease and grace
- Philco Automatic Tuning  - a flick of your fingers and in comes
your favorite station, tuned with absolute accuracy... instantly... perfectly.
-
Magnetic Tuning
- Philco High-Fidelity  - twice the tonal range of ordinary radios....
for glorious realism..
-
Acoustic Clarifiers - prevent "boom"
-
Wide Angle Sound Diffusion
- Inclined Sounding Board - brings music up to ear level
-
Cathedral Speaker - exclusive Philco two-in-one High Fidelity
speaker
- The Philco Foreign Tuning System - with spread band dial..
which doubles the number of  foreign stations you can get  and enjoy...
assures you mastery of overseas reception...
- Fifteen Philco Tubes and five tuning ranges covering everything
that's interesting on the air. Anti-distortion Beam-Output Tubes...
-
Individual and Personal Control of both treble and bass
- Everything you could wish for - in a cabinet of thrilling beauty..
with Protective Back.
"Tune easily, gracefully, Automatically!                ...sitting or standing...!"
"Performance that is a revelation! ..tone that is glorious in its
realism..."
All you could ask in radio.
Philco's Ten Millionth Radio - a 38-116XX

During the late fall of 1937, Philco announced the prod-
uction of its ten millionth radio - a model 38-116XX. To
commemorate the occasion, Philco presented the set to
the Walter Reed Hospital in Washington D.C. at a cere-
mony that was a feature of the 1937 Armistice Day celeb-
rations in the Nation's capital. The set was presented to
the veterans in the hospital by Boake Carter, famous
Philco Radio news commentator, representing the Philco
Radio and Television Corporation. Secretary of War,
Harry H. Woodring accepted the radio on behalf of the
veterans and servicemen. Every seat in the auditorium in
the Red Cross House at the Great Army Medical Center
was occupied by soldiers and patients.

On a silver plate attached to the base of the inclined

control panel of the radio, was the following inscription:-








Replicas of the ten millionth Philco were presented
simul-
taneously with the Armistice day ceremony at the Walter
Reed Hospital to the various veterans' hospitals through-
out the country.

Secretary Woodring, responding to the theme of the

ceremony, said "I know of no greater pleasure than to
come here and accept this generous gift on behalf of the
Walter Reed hospital. To my mind there is no greater
invention than the radio, especially for those who are
hospitalized. Philco has given its 10,000,000th radio to
the Walter Reed hospital. I recall that when Philco prod-
uced its 7,000,000th radio, it gave that instrument to the
Warm Springs Foundation, in which our president is so
interested. I say now that we express our admiration to
Philco for this gift". Summary and extracts from a report in: The
Charleston Daily Mail, Nov 21 1937, p 10.

As well as donating a number of "exact" replicas of the
ten-millionth Philco to veteran's hospitals throughout the
USA, Philco offered a limited number for sale. They were
sold with a plaque affixed to the base of the inclined con-
trol panel, bearing an engraving of the purchaser's name
preceded by the words:- "Exact Replica of the Ten Milli-
onth Philco. Built for" (click center ad  thumbnail below).

To promote sales of the 38-116XX at this time, Philco ran

a national advertising campaign based around their
"crowning achievement in radio", the ten-millionth set.
Interested parties were invited to visit their local dealer-
ship to see and hear an exact replica of the radio. Once
there, they could submit a coupon for a free copy of a
Souvenir Brochure entitled "The Story Behind The Ten
Millionth Philco" and a copy of "The Philco Mystery
Book", containing an entry blank for "Philco's Radio
Mystery Contest" offering $50,000 in cash prizes. In the
store, of course, they would learn how easy it was to own
a 38-116XX radio by taking advantage of Philco's "only a
few dollars down" financing offer, combined with gener-
ous trade-in allowances against their old set. On a final
note, the 38-116XX was originally listed at $200 in east-
ern regions of the USA, but at the time of the ten-millionth
set promotion in late fall, it was being advertised at
around $230.
"This, the ten millionth Philco, is presented to the
World War veterans in the Walter Reed Hospital
in the hope that it will bring them in closer
contact with 'the good things on the air'.
November Eleventh, 1937
".
The meaning of the 'XX' in the Philco 38-116XX

Back in early 1932 Philco introduced the inclined sounding board
and heralded it as a revolution in radio. Models incorporating this
feature had an 'X' appended to the model number (e.g. 112X).
When Philco introduced the inclined control panel in 1937, it was
only natural for them to add a second 'X' to the model number of
sets incorporating both features. These became known simply as
the Philco Double-X models.
Philco 38-116XX (1938 season)
Philco 38-116XX
Sound Diffuser and Clarifiers
Two-Piece 14-inch speaker
Protective Rear Cover
Ten Millionth Philco Newspaper ad (Nov 1937)
Ten Millionth Philco Newspaper ad (Nov 1937)
PHILCO MODEL 116 SERIES
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