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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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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August 1932 Radio-Craft[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.
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.
(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.
Condensers C1 to C9, tuning or trimming condensers. Condensers C10, C22, C23, are 110 mmf. units; C11, C12, C13, C18, C19, 0.05-mf.; C14, C17, 0.09-mf.; C15, C24, C25, 0.25-mf.; C16, 35 mmf.; C20, 1.0 mf.; C21, C27, 0.01-mf.; C26, C31, C33, 0.5-mf.; C28, C29, C30, tone control condensers; C32, 0.002-mf. (dotted; see text); C34. C38, C39, 0.015-mf.; C35, 0.18-mf.; C36, C37, 6 mf. (electrolytic); C5.A, 700 mmf.
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 161 Radio Service Data Sheets as of January 3, 2017.