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Zenith Radio Corporation MHT14 Service Manual

1962 high fidelity and stereo fm models
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ERVICE MANUAL
962 HIGH FIDELITY
AND STEREO FM MODELS
ZENITH
RADIO
CORPORATION
600
DICKENS AVENUE
CHICAGO 39, ILLINOIS
PRICE 60 CENTS
HF-8

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Summary of Contents for Zenith Radio Corporation MHT14

  • Page 1 ERVICE MANUAL 962 HIGH FIDELITY AND STEREO FM MODELS ZENITH RADIO CORPORATION DICKENS AVENUE CHICAGO 39, ILLINOIS PRICE 60 CENTS HF-8...
  • Page 3 INDEX CHASSIS PARTS LIST TUBE LAYOUT SCHEMATIC PAGE PAGE PAGE MODEL 30, 60, 61 HT14 30, 59, 60 30, 39 HT15 See Service anual HF7 GV21 HV22 H910 SFH2500T 30, 57, 60, 61 31, 33 30, 31, 32 H2600 SFH2502T 30, 57, 59, 60 35, 4Q 30, 39, 34...
  • Page 4 FEATURES OF SFH & MH HIGH SPEAKER CHASSIS CABINET MODEL MAGNET EIA POWER SIZE FINISH COLOR MODEL TYPE STYLE MATERIAL (WT. OZ.) OUTPUT (IN.) — — HT14C DROP-I N-TUNER A -F Tuner 9H21 — A -F Tuner HT15C DROP-IN-TUNER 9H20 ..
  • Page 5 FIDELITY & STEREO FM MODELS § RADIAL RECORD CHANGER (SEE NOTES) INDI ­ CONTROL TYPE OF REVER ­ CATOR SOUND STYLUS PANEL CARTRIDGE IDENTIFICATION BERATOR TYPE MOUNTING SPEAKER LIGHT — — — — Die-Cast ZENITH-Crest — Escutcheon — — — —...
  • Page 6 FEATURES OF SFH & MH HIGH SPEAKER CABINET CHASSIS MODEL SIZE MAGNET EIA POWE MATERIA L FINISH STYLE COLOR MODEL TYPE (WT. OZ.) (IN.) OUTPUT SFH2S15YT Console Wood Paint Ebony Phono only 40W. 2-3% 4H30 (lift lid) 3.16 2-5% 7H30 13.0 2-12 SFH2515ET...
  • Page 7 FIDELITY & STEREO FM MODELS § RADIAL INDI ­ RECORD CHANGER (SEE NOTES) TYPE OF CONTROL REVER ­ SOUND CATOR BERATOR PANEL IDENTIFICATION TYPE MOUNTING CARTRIDGE STYLUS SPEAKER LIGHT Shelf Diamond etal Plate ZENITH Extended 169-159 142-121 Stereophonic High Sapphire Fidelity —...
  • Page 8 FEATURES OF SFH & MH HIGH CABINET MODEL CHASSIS SPFA k ’ PD STYLE EIA POWER MATERIAL SIZE FINISH MAGNET COLOR MODEL TYPE OUTPUT (IN.) (WT. OZ.) H3388W Console Wood Wood Walnut 16H22Q TV-Phono 20W. 2-sy 4 (lift lids) 8H30 A -F 2-12 HT15C...
  • Page 9 FIDELITY & STEREO FM MODELS INDI ­ § RADIAL RECORD CHANGER (SEE NOTES) TYPE OF CONTROL REVER ­ SOUND CATOR IDENTIFICATION CARTRIDGE STYLUS PANEL BERATOR MOUNTING TYPE SPEAKER LIGHT Shelf Diamond etal Plate ZENITH Stereophonic Provisions FR101, 142-121 169-159 Sapphire High Fidelity —...
  • Page 10 GENERAL STEREOPHONIC (MULTIPLEX) TRANSMITTER BLOCK DIAGRAM A new form of F broadcasting has been approved The two basic components necessary for any stereo by the Federal Communications Commission. This system are right and left audio channel information. will provide stereophonic F broadcasting and recep ­...
  • Page 11 BLOCK DIAGRAM 2H26 MULTIPLEX RECEIVER...
  • Page 12 sion ’ s radiation limits, it was felt that these goals MULTIPLEX RECEIVER could best be achieved by having the F tuner sepa ­ The 12H26 chassis is used to describe the circuitry rate from the A tuner. In this manner all long leads, of Zenith F stereophonic multiplex receivers, since band switching and other associated circuitry that it includes all the features that are basically com ­...
  • Page 13 the I.F. transformer primary... in this manner, gain TAPPED DOWN I.F. TRANSFORMER is reduced. However, at the same time, the Q of the In this receiver more than sufficient 455 KC IF gain coil and selectivity are retained. is available and it may be desirable to reduce it to eliminate overload problems.
  • Page 14 AGC SOURCE AND NETWORK AGC voltage.) 2. 6JK8 F -RF amplifier grid. A.G.C. voltage developed from the 6EQ7 diode plate 3. 6BA6 first IF amplifier grid. controls the preceding circuits in the following se ­ 4. 6BE6 A converter grid. quence.
  • Page 15 RATIO DETECTOR 2. L + R audio voltage. The ratio detector circuit may be considered stan ­ 3. Two L - R 38 KC side bands. dard; it utilizes two diodes of the 6BC7 triple diode. This information is separated, and the 19 KC pilot The composite output from this ratio detector con­...
  • Page 16 103-34 diodes (X2 and X3) operating as a full wave 9 KC PILOT AMPLIFIER MUTE ­ unfiltered rectifier, act as a frequency doubler. The GATE VOLTAGE SOURCES and DOUBLER output of this full-wave rectifier is a series of 38 KC The 19 KC pilot signal from the output of the ratio positive pulses.
  • Page 17 FM TUNER MONAURAL-STEREO SWITCH In some locations, the available signal may vary and as a result, even though initially there was suffi ­ cient incoming signal to overcome the back bias on the 6AW8A 19 KC amplifier, with reduced signal there is a possibility that reception will be quite noisy and perhaps even distorted.
  • Page 19 will obtain an audio voltage — (L - R). Since we are 38 KC SUB CARRIER AMPLIFIER again feeding an L + R audio voltage to the center The 38 KC DC pulses from the doubler are used to point of this transformer, we now add; create the 38 KC carrier for insertion with the two - (L - R) + (L + R) = L - R 38 KC side bands.
  • Page 20 During stereo operation when a 19 KC signal arrives in sufficient strength to overcome the back bias on the 6AW8A, the tube will begin to conduct and as a result of its drawing current, the screen voltage will drop to approximately *70 volts. With a 19 KC signal now passing through the plate circuit, there will be *95 volts P-P at the plate and approximately *200 volts P-P will be developed across the primary of...
  • Page 21 a like portion of out of phase components of right EXTENDED STEREO OPERATION (R) information into the left channel, we will fulfill CHASSIS 4H30 & 4H25 the requirements and obtain the extended spatial Since stereophonic reproduction depends on the dif ­ effect.
  • Page 22 which delays the signal. This signal is then ampli ­ REVERBERATION SYSTEM fied in the 12AX7A amplifiers and fed to % of the MODEL HV22 - CHASSIS 2H23 6BH8 phase inverter. A positive portion of (L + R) This extended reverberation kit functions in the same D from the plate (Pin 3) is fed to the right audio chan ­...
  • Page 24 MUTING CONTROL the line cord is unhanked and stretched out in back of the receiver; do not coil or bunch it up. Also, The 25 K muting control which supplies a back bias try the plug both ways in the power socket for the voltage to the cathode of the 19 KC pilot amplifier position which gives best F reception.
  • Page 25 Chassis 2H26. 4H25 icro-volts AGC Voltage Input at RF Coil 1.32 1.72 *2.95 3.85 10 K 20 K 50 K B. Connect scope or V.T.V. . to junction of 100 ohm 100 K and 330 mmf capacitor. This 100 ohm resistor is connected to terminal #6 of the ratio detector transformer.
  • Page 26 □ <✓> < < < ______ - RF and IF Alignment Procedure for Chassis 9H20-9H2...
  • Page 27 •J o v — < •J oo OQ </> < RF and IF Alignment Procedure for Chassis 9H22...
  • Page 28 i — i 1 — I 8> <✓> < < < < r — ( < RF and IF Alignment Procedure for Chassis 2H26«- 4H25...
  • Page 29 2H23 SCHEMATIC FOR HV22 2H23 TUBE LAYOUT FOR HV22...
  • Page 30 SCHEMATIC FOR S-5370 FM TUNER USED WITH CHASSIS 9H20, 9H2 , 2H26 & 4H25...
  • Page 31 SCHEMATIC FOR MODELS SFH2500T & MH2600 TUBE LAYOUT FOR MODELS SFH2500T & MH2600...
  • Page 32 SCHEMATIC FOR MHT- 4 TUNER USED ON MODELS SFH2500T & MH2600...
  • Page 33 TUBE LAYOUT FOR MHT- 4 TUNER USED ON MODELS SFH2500T & MH2600...
  • Page 34 SCHEMATIC FOR MODELS SFH2502T, MH2602, SFH2503T, MH2603 & MH2786...
  • Page 35 4G2 -5G29 TUBE LAYOUT FOR MODELS SFH2502T, MH2602, SFH2503T, MH2603 SFH2504T, MH2604, SFH2505T, MH2605, MH2607 & MH2786...
  • Page 36 5G29 SCHEMATIC FOR MODELS SFH2504T, MH2604, SFH2505T, MH2605 & MH2607...
  • Page 37 8H30 SCHEMATIC FOR MODELS H2787, H2789, H3388, MH2787, MH2789 & MH3388...
  • Page 38 8H30 TUBE LAYOUT FOR MODELS H2787, H2789, H3388, MH2787, MH2789 & MH3388...
  • Page 39 9H20 SCHEMATIC FOR MHT 5 TUNER APPLICABLE TO MODELS SFH2502T, MH2602 SFH2503T MH26O3 SFH2504T, MH2604, SFH2505T, MH2605, MH2607, SFH25 5T, MH26 5, MH2786, MH2787, MH2789 & MH33&8*...
  • Page 40 9H20 TUBE LAYOUT FOR MHT 5 TUNER APPLICABLE TO MODELS SFH2502T, MH2602, SFH2503T, MH2603, SFH250<T, MH2604, SFH2505T, MH2605, MH2607, SFH25 5T, MH26 5, MH2786, MH2787, MH2789 & MH3388...
  • Page 41 9H22 SCHEMATIC FOR MH9 0 MULTIPLEXER...
  • Page 42 9H22 TUBE LAYOUT FOR MH9 0 MULTIPLEXER...
  • Page 43 4H30 SCHEMATIC FOR MODELS SFH25 5T & MH26 5...
  • Page 44 7H30 SCHEMATIC FOR MODELS SFH25 5T & MH26 5...
  • Page 45 4H30 TUBE LAYOUT FOR MODELS SFH25 5T & MH26 5 7H30 TUBE LAYOUT FOR MODELS SFH25 5T & MH26 5...
  • Page 46 3H32 SCHEMATIC FOR MH2635...
  • Page 47 2H26 SCHEMATIC FOR MODELS MH2635...
  • Page 48 3H32 - 2H26 TUBE LAYOUT FOR MODEL MH2635...
  • Page 49 SCHEMATIC FOR MODELS MH2670, MH2675 & MH2685...
  • Page 50 4H25 SCHEMATIC FOR MODELS MH2670, MH2675 & MH2685...
  • Page 51 4H25 TUBE LAYOUT FOR MODELS MH2670, MH2675 & MH2685...
  • Page 52 TUBE LAYOUT FOR MODELS MH2670, MH2675 & MH2685...
  • Page 53 DIAL CORD DRIVE FOR MHT 5 CHASSIS 9H20...
  • Page 54 DIAL CORD DRIVE FOR MHT 4 CHASSIS 9H2...
  • Page 55 DIAL CORD DRIVE FOR MH9 0 CHASSIS 9H22...
  • Page 56 DIXL CORD DRIVE FOR MODELS MH2635, MH2670, MH2675 & MH2685 CHASSIS 2H26 & 4H25...

  • Page 57: Numerical Parts List

    NUMERICAL PARTS LIST CHASSIS 2H23 CHASSIS 3H32 (Cont ’ d.) REF. PART REF. PART DESCRIPTION DESCRIPTION 22-2340 fd. Electrolytic 400 V 22-1561 25 V 1 mfd 22-3404 400 V 22-2376 500 V 40 mfd 22-2376 500 V 450 V 22-3486 10 mfd mf.
  • Page 58 CHASSIS 5G29 (Cont ’ d.) CHASSIS 4H30 PART REF. PART- REF. DESCRIPTION DESCRIPTION ,0022 mfd Disc 22-18 500 V 4 22-2703 mf. Disc .0047 mfd 22-1842 200 V 1 mf. Disc 22-2703 47 mmf Disc 22-2376 SOO V 22-360:8 mf. Disc 22-18 .0022 mfd Disc 500 V...
  • Page 59 CHASSIS 7H30 (Cont ’ d.) CHASSIS 8H30 (Cont ’ d.) REF. PART REF. PART escription DESCRIPTION fd. Capacitor 22-2436 22-1841 600 V .0022 fd. Tubular 200 V C14A fd. Capacitof 200 V fd. Electrolytic 450 V 22-1777 C14B 22-1841 fd. Capacitor 600 V 22-3099 fd.
  • Page 60 CHASSIS 9H20 (Cont ’ d). CHASSIS 9H2 PART REF. REF. PART DESCRIPTION DESCRIPTION 22-3 fd. Disc 500 V 22-8 .0022 fd. Disc 1000 V fd. Paper 22-3626 100 V 22-3 fd. Disc 500 V 22-3635 2200 mfd. 300 V 22-8 .0022 fd, Disc 1000 V...
  • Page 61 CHASSIS 9H2 (Cont ’ d.) CHASSIS 9H22 (Cont ’ d.) REF.' PART PART DESCRIPTION DESCRIPTION } L24 S-54065 Trap Coil 67 KC 22-13 .0033 Disc 500 V S-54467 Detector Coil C50A 60 mfd 150 V S-54066 Input Coil C50B 22-3636 150 mfd Electrolytic 150 V C50C...
  • Page 62 CHASSIS 2H26 (Cont ’ d.) CHASSIS 2H26 (Cont ’ d) REF. PART DESCRIPTION PART REF. DESCRIPTION 10W ( 63-4395 2200 Det. Tuning C38C 22-3594 1200 63-4475 Det. Trimmer C38D 20 W 10 K 63-4810 Osc. Tuning C38E Osc. Trimmer C38F 2nd F I.F.
  • Page 63 CHASSIS 4H25 (Cont ’ d) CHASSIS 4H25 (Cont ’ d.) REF. PART REF. PART DESCRIPTION DESCRIPTION 1 C37 22-1778 .047 fd. Paper 200 V C105 22-3518 .047 fd. Paper 200 V C38A Ant. Tuning Cl 06 22-3518 .047 fd. Paper 200 V C38B Ant.
  • Page 64 ZENITH RADIO CORPORATION DICKENS AVENUE CHICAGO 39. ILL. HF8-RR Printed in U.S.A*...

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