Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
At
least for now, I am going to only scan and post Radio Service Data Sheets like this one featuring the Philco Model
15 Series, 11-Tube Superheterodyne Chassis in graphical format, and run OCR on them to separate the textual content
and make it searchable. There are still many people who restore and service these vintage radios, and often it can
be difficult or impossible to find schematics and/or tuning information. I will keep a running list of all data
sheets to facilitate a search. The hilco Model 15 Series, 11-Tube Superheterodyne photo was found on the
PhilcoRadio.com website.
Philco Model 15 Series, 11-Tube Superheterodyne Chassis Radio Service Data Sheet
(Used in Models 15X and 15DX receivers; and includes inclined sounding board, twin reproducers, tone control,
A.V.C., visual tuning, local-distance switch.)
A feature of this chassis design is the exceptionally fine quality of the reproduction. Note that tubes of the
6.3-volt or "automotive" type are used in this ultra-modern receiver, a product of the Philco Radio & Television
Corp. The following quotation is of particular interest.
"In efficiency, in economy of current and space, in uniformity, in freedom from trouble and in all-around performance,
the new Philco 6.3·volt universal-service tubes are superior to any tubes that we know of, past or present.
"We will standardize on 6.3-volt heater type tubes, since their use permits application to automotive receivers
and D.C. sets, as well as to A.C. instruments; thus, all new developments in future Philco tubes will be immediately
available for all these classes of service."
Following is a list of the features of this set, as furnished by the factory: Inclined sounding board, twin-reproducers,
A. V.C., automatic tuning silencer, distance switch, illuminated grille, tone control, shadow tuning, glowing-arrow
station finder, station-recording type of dial.
The resistors in the Model 15 chassis should measure as follows: R2, R17, 10,000 ohms; R3, R5, R18, .49-meg.;
R4, 0.16-meg.; R6, 51,000 ohms; R7, 200 ohms;: R8, R14 R16, 1.0 meg.; R, 13,000 ohms: R10, 1,000 ohms; R11, 99,000
ohms; R12, 0.25-meg. (dotted; see text); R13, R19, 5,000 ohms; R15, 25,000 ohms; R20, 0.24-meg.; R21, R22, 50 ohms;
R23, 205 ohms.
The reproducer system of this receiver deserves special mention. Due to the fact that there are two separate
dynamic reproducers operating from a single receiver output, it is absolutely essential that the instruments be
correctly "poled" - that is, the field and voice coils must be connected so that the correct "phase" relation is
maintained between the two units. (Both diaphragms moving in or out at the same time.) For this reason a detail
illustration of the reproducer leads, showing their color code and connections, is reproduced in this Data Sheet.
Chasses stamped at rear with a circle around Nos. 20 and 21 must have R12 and C32 added to reduce distortion
due to powerful local stations: Nos. 22 and 23 have C32 but may require R12 ; subsequent chasses are equipped with
both.
"Both speakers have identically the same frequency response characteristics," states the manufacturer. The two
reproducers arc used to obtain more uniform sound distribution. An echo-absorbing screen at the rear of the cabinet
prevents echo and blur - and tends to increase front-projected sound volume .
The power rating of the set is 115 watts. The tubes in the Model 15 chassis are very economical in their filament-current
requirements. The types '37 and 44 tubes consume only 0.3-A; the 42's (the output pentodes), 0.7-A.; the '80, 2.
A. The filaments of all of these tubes, except the '80, are rated at 6.3 V.; the '80, 5 volts.
With an A.C. line potential of 115 volts, volume control at maximum, with the station selector turned to the
low-frequency end and the power switch in the "middle" position, the following readings are normal: Plate potential
(measured to cathode), V1, 165 volts; V2, V4, 250 volts; V3, 60 volts; V5, 275 volts; V6, zero; V7, 75 volts; V8,
100 volts; V9, V10, 255 volts; V11, 320 (per plate). Screen-grid (to cathode), V1, 55 volts; V2, V4, V5, 90 volts;
V9, V10, 270 volts. Control-grid (to cathode), V1, V3, V9, V10, 15 volts: V2, V4, 0.85-volt; V5, 3.3 volts; V6,
V8, 0.2-volt; V7, 0.4-volt. Cathode (to filament), V1, 30 volts; V2 to V9, 10 volts; V10, 15 volts; V2, V4, 0.85-
volt; V5, 3.3 volts; V6, V8, 0.2-volt; V7, 0.4-volt. Cathode (to filament), V1, 30 volts; V2 to V9, 10 volts; V10,
V11, 15 volts.
Posted July 27, 2015
Radio Service Data Sheets
These schematics, tuning instructions, and other data are reproduced from my
collection of vintage radio and electronics magazines. As back in the era, similar
schematic and service info was available for purchase from sources such as
SAMS Photofacts, but these printings
were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of
December 28, 2020.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
