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RCA Radiola 17 Service Notes

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RCA
Radiola 17
SERVICE NOTES

RCA Radiola 17

First Edition—Nov. 1927 R17—1
Radio Corporation of America
SERVICE DIVISION OF THE PRODUCTION AND SERVICE DEPARTMENT
233 BROADWAY, NEW YORK CITY
DISTRICT SERVICE STATIONS
326 Broadway 1412 Monroe St., N. W. 2001 West Pershing Road 274 Brannan St.
New York City
Washington, D. C.
Chicago, 111.
San Francisco, Cal.

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  • Page 1: Rca Radiola 17

    Radiola 17 SERVICE NOTES RCA Radiola 17 First Edition—Nov. 1927 R17—1 Radio Corporation of America SERVICE DIVISION OF THE PRODUCTION AND SERVICE DEPARTMENT 233 BROADWAY, NEW YORK CITY DISTRICT SERVICE STATIONS 326 Broadway 1412 Monroe St., N. W. 2001 West Pershing Road 274 Brannan St.
  • Page 2 A WORD OR TWO ABOUT SERVICE Service goes hand in hand with sales. The well informed RCA Dealer renders service at time of sale in affording information as to proper installation and upkeep. Subsequent service and repair may be required by reason of wear and tear and mishandling, to the end that Radiola owners may be entirely satisfied.

  • Page 3: Table Of Contents

    Replacing Audio Transformers ........28 Replacing Output Transformer........28 ILLUSTRATIONS Page Page RCA Radiola 17 ....„......:..1 …….…..17 View of Pilot Light Socket and Canopy. Top View of Chassis Assembly......... 4 Wiring Diagram of Sub-Chassis Assembly ……..18 Socket Power Unit Showing Parts........5 Continuity Wiring Diagram of S.P.U......

  • Page 4: Top View Of Chassis Assembly

    POWER CABLE TUNING CONDENSERS OUTPUT TRANSFORMER ANTENNA AND GROUND CONNECTIONS Figure 1—Top view of chassis assembly showing the principal parts.

  • Page 5: Socket Power Unit Showing Parts

    STRIP Figure 2—Socket Power Unit showing various parts. and Radiotron UX-280 in a plate and grid supply unit makes Radiola 17 a complete socket power receiver operating on 105-125 volts, 50 to 60 cycle A. C. lines. Very little service work should be required on Radiola 17. However, the following notes are published for the guidance of those called upon to locate and remedy any trouble that may occur.

  • Page 6: Radiotron Sequence

    The last stage, Radiotron No. 6, employs power amplifier Radiotron UX-171. (2) CIRCUIT CHARACTERISTICS The following principles are incorporated in the circuit design of Radiola 17 (Figure 4 and 4A.) 1. A three-gang condenser, employed to tune two of the radio frequency circuits and the detector circuit, provides one tuning control.

  • Page 7: Radiotrons

    7. Radiotron UX-171 in the last audio stage provides ample volume without distortion in loudspeaker reproduction. Figure 4A—Schematic circuit diagram of socket power unit. The various circuit characteristics of Radiola 17 provide for easy installation and simple operation coupled with quality reproduction delivered to the loudspeaker. (3) RADIOTRONS Radiotrons UX-226 are used in all radio frequency amplifying stages and in the first audio amplifying stage.

  • Page 8: Antenna Installation (Outdoor)

    Figure 5—Radiotron socket contacts ANTENNA INSTALLATION (Outdoor Type) Due to the high sensitivity of Radiola 17 the most efficient antenna system is one of approximately 25 feet in length—depending upon local conditions—measured from the far end of the antenna to the ground connection. It should be erected as high as can be conveniently arranged and as far removed from all obstructions as possible.

  • Page 9: Ground

    It is recommended that the service man experiment with various grounds, and employ the one giving the best results. Radiola 17 is capable of receiving over good distances when connected to an efficient antenna and a low resistance ground.

  • Page 10: Antenna System Failures

    (8) RADIOTRON SOCKETS The sockets in Radiola 17 are of the standard gang UX and UY type (Figure 5). The three-gang socket is for the radio frequency amplifiers; the single socket—a five-prong detector socket is for Radiotron UY-227 and the two-gang socket is for the audio frequency amplifiers. Care must be exercised when inserting Radiotrons in the sockets.

  • Page 11: Loose Volume Control Contact Arm

    The potentiometers (Part I, Section 19) should be readjusted for the position of minimum hum whenever the Radiotron prongs are cleaned. The prongs should be cleaned by using a piece of fine sandpaper (Figure 6). The use of emery cloth or steel wool is not recommended. Before re-inserting Radiotrons in their sockets wipe the prongs and base carefully to make certain that all particles of sand are removed.

  • Page 12: Mechanical Hum

    After considerable wear, or extreme changes of temperature the cable may become slack. To take up this slack open lid of cabinet and turn the cable adjusting screw with clamp until the cable is taut. (See Figure 9.) In extreme cases as might occur after considerable use and several adjustments this screw may become seated thus allowing no further tightening of the cable.

  • Page 13: Broken Condenser Drive Cable

    (14) LOUDSPEAKER POLARITY Due to Radiola 17 using an output transformer, there is no polarity to the output current of the receiver. Consequently, when connecting any type of loudspeaker (either horn type or cone type) the speaker should be connected in the manner that gives the most pleasing reproduction.

  • Page 14: Schematic Circuit For Resistance Measurement

    3. Antenna lead too close to third E. F. transformer. 4. Detector tube howling. In the case of No. 1 the grid resistance of Radiola 17 may be checked by means of a resistance bridge. If' a resistance bridge is not available the voltmeter-ammeter method gives accurate results provided the meters used are calibrated accurately.

  • Page 15: Distorted Reproduction

    The correct adjustment of these potentiometers is described in Part I, Section 19 Should Radiola 17 become noisy in operation or signals come in and die out abruptly with periods of hum or no reception, test in the following manner: (a) Disconnect antenna and ground leads.

  • Page 16: Adjusting Potentiometer Tor Minimum Hum

    227. detector tube with another of a similar type or change the position of the loudspeaker. In extreme cases both remedies may be necessary. Three potentiometers are provided in Radiola 17 for the suppression of any AC hum These potentiometers are adjusted for the correct electrical center of the filaments of Radiotrons UX-226, UY-...

  • Page 17: View Of Pilot Light Socket And Canopy

    (a) Place set in normal operation with loudspeaker connected. (b) Remove Radiotrons 2 and 3, counting from left to right (first audio and detector stages facing front of Radiola). (c) Locate position of three potentiometers in power unit. (d) Adjust potentiometer, located at extreme right when facing front of Radiola (Figure 13), for position of minimum hum.

  • Page 18: Line Control Switch

    justed for a further minimum value, which will not now be located at one of the extreme positions. (c) After making any potentiometer adjustment, further reduction of hum may be attempted by reversing the input plug. When adjusting the potentiometer at the extreme right with a metallic screw driver a flash will occur from the screw driver to any part of the frame that the screw driver may touch.

  • Page 19: Wiring Cable

    115 to 125 the switch should be placed at the 120-volt position. (21) WIRING CABLE On examination of the chassis wiring in some models of Radiola 17 there will be noticed a green dead end wire, about 6 inches long, connected to the third Figure 16—Continuity wiring diagram of socket power wit and color...

  • Page 20: Voltage Readings

    (24) VOLTAGE READINGS When checking a Radiola 17 for possible defects it is good practice to check the voltage of the various sources of current. To do this a service man will need both an A. C. and a D. C. voltmeter, the D.

  • Page 21: Grid And Plate Voltages

    (25) GRID AND PLATE VOLTAGES In order to intelligently service Radiola 17 it is well to have a good understanding of how the various circuits function.. The plate supply and filament Figure 18—Schematic circuit for securing grid biasing voltages.

  • Page 22: Heating Of Cabinet

    (26) HEATING OF CABINET Under normal conditions when the lid of Radiola 17 is closed the interior parts in the vicinity of Radiotron UX-280 will become quite warm. This is a normal condition. It keeps all the mechanism dry...

  • Page 23: Continuity Tests

    (27) RADIOLA 17 CONTINUITY TESTS The following tests will show complete continuity for the Receiver Assembly (Figure 15) and the Socket Power (Figure 16). Disconnect the antenna and ground leads, the cable connecting the S. P. U. to the receiver assembly, and the A. C. supply cord at its outlet. Do not tamper with the main tuning condensers.

  • Page 24: Replacing Volume Control

    SOCKET POWER UNIT CONTINUITY TESTS and Disconnect Remove Radiotron UX-280 Cable at Terminal Strip Terminals Correct Effect Incorrect Effect Caused By Across terminals 1 to 2 Closed Open UX-226 filament winding and Across terminals 3 to 4 Closed potentiometer Open UY-227 filament winding and Across terminals 5 to 6 Closed potentiometer Open UX-171 filament winding and...

  • Page 25: Replacing Radio Frequency Coils

    the back opening. See Figure 19. This will allow an examination of the parts and provide access to those necessary to replace. 5. Remove the two screws that hold the volume control to the metal chassis. (Figure 7.) 6. Tag and unsolder all leads to the volume control. The volume control may now be removed and the new one placed in position occupied by the old one.

  • Page 26: Replacing Radiotron Gang Sockets

    7. Return chassis assembly to cabinet and replace all screws and knobs. (3) REPLACING RADIOTRON GANG SOCKETS The Radiotron sockets of Radiola 17 are of the gang variety, using one detector socket, a two-gang A.F. socket strip and one three-gang socket strip for the radio frequency amplifier tubes.

  • Page 27: Replacing Large By-Pass Condensers

    2. Unsolder four connections to condenser. 3. Remove three screws from under side of chassis that holds condenser assembly. 4. The assembly may now be removed and the new assembly placed in the position occupied by the old assembly. 5. Replace three screws that hold assembly in place and resolder leads. 6.

  • Page 28: Replacing Audio Transformers

    (7) REPLACING OUTPUT TRANSFORMER The output transformer of Radiola 17 is held in place by means of four tabs which hold the output transformer to the vertical part of the chassis frame. A step by step procedure for replacing this unit is as follows: 1.

  • Page 29: Replacing Dial Scales

    3. Starting from the rear grooved drum place eye of cable over pin, which should be in a horizontal position facing the socket power unit, and wind on three complete turns, and then bring cable up to large drum. 4. Now bring cable over the large drum. Turn drum so that cable adjusting screw is on top. Pass cable over groove until point is reached where there is a slot in the drum for passing cable to the track on other side of drum.

  • Page 30: Replacing Power Cable

    (11) REPLACING FILTER CONDENSER ASSEMBLY The following procedure should be used when replacing the filter condensers of Radiola 17: 1. Remove the seven screws holding the wooden back to the cabinet.

  • Page 31: Replacing Either Power Transformer Or Filter Reactor

    U. to cabinet in the reverse order. (14) REPLACING MISCELLANEOUS PARTS IN S. P. U. The potentiometers, line switch, UX-280 socket and resistance unit in Radiola 17 may become defective and require replacement. They are all attached to the base by means of machine screws and nuts and replacement is very simple.
  • Page 32 SERVICE DATA CHART Before using the following Service Data Chart, when experiencing no signals, weak signals, poor quality, noisy or intermittent reception, howling and fading, first look for defective tubes, or a poor antenna system. If imperfect operation is not due to these causes the "Service Data Chart" should be consulted for further detailed causes.

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