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Zenith HF-24 Service Manual

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ERVICE MANUAL
IG
FIDELITY
AND STEREO FM MODELS
ZENIT RADIO CORPORATION
1900 N. AUSTIN AVENUE
C ICAGO, ILLINOIS 00039
F-24
PRICE $1.50
PART NO. 923-653

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  • Page 1 ERVICE MANUAL FIDELITY AND STEREO FM MODELS ZENIT RADIO CORPORATION 1900 N. AUSTIN AVENUE C ICAGO, ILLINOIS 00039 F-24 PRICE $1.50 PART NO. 923-653...
  • Page 2 TT 5 ' ----- WT — rr...
  • Page 3 S-83179 Refer to HF 18, HF 18-1, HF 19 HF 22 SPEAKER WIRING 31,32 HF 17 is Zenith No. 923-521 HF 17-1 is Zenith No. 923-529 HF 17-2 is Zenith No. 923-555 HF 18 is Zenith No. 923-558 HF 18-1 is Zenith No. 923-576 HF 18-2 is Zenith No.
  • Page 4 FEATURES OF IG FIDELITY & STEREO FM MODELS SPEAKERS CABINET C ASSIS yOlCECOIL SIZE PART IMPED. MODEL STYLE COLOR MODEL TYPE POWER (In Inches) NUMBER (In Ohms) OUTPUT 1-3/2 849-48B B505B Portable Blue & Phono Only Note 2 (Removable White (RA7) Lid) B505F...
  • Page 5 FEATURES OF IG FIDELITY & STEREO FM MODELS OT ER FEATURES RECORD C ANGER POWER REMOTE RECORD 45 RPM TAPE STYLUS PART SPEAKER INDICATOR MOUNTING CARTRIDGE PROVISION STORAGE NOTE 1 ADAPTER NUMBER PROVISION LIG T 827-1 8B 942-8B Manual Integral 856-1 5B Player 942-8B...
  • Page 6 FEATURES OF IG FIDELITY & STEREO FM MODELS CABINET C ASSIS SPEAKERS VOICECOIL PART SIZE MODEL STYLE COLOR TYPE MODEL POWER IMPED. NUMBER (In Inches) OUTPUT (In Ohms) B545W Portable Walnut 2X1W 2-5% Phono Only 964-24020 (With Handle, Detachable Speaker Enclosures) 2-6x9 B553W...
  • Page 7 FEATURES OF IG FIDELITY & STEREO FM MODELS OT ER FEATURES RECORD C ANGER REMOTE POWER 45 RPM TAPE RECORD STYLUS PART SPEAKER INDICATOR CARTRIDGE MOUNTING PROVISION STORAGE NOTE 1 ADAPTER NUMBER PROVISION LIG T 142-175 S-72648 169-407 Hinged 56-560 Shelf S-72648 142-175...
  • Page 8 FEATURES OF IG FIDELITY & STEREO FM MODELS CABINET C ASSIS SPEAKERS VOICECOIL PART SIZE MODEL STYLE COLOR MODEL TYPE POWER IMPED. NUMBER (In Inches) OUTPUT (In Ohms) C920W Console Walnut 21BT34Z1 FM/AM/Phono 2x1 OW 49-1094 2-3% Note 2 (Lift Lid) 49-1166 2-Horn (HF23)
  • Page 9 FEATURES OF IG FIDELITY & STEREO FM MODELS OT ER FEATURES RECORD C ANGER REMOTE POWER RECORD TAPE STYLUS 45 RPM PART SPEAKER INDICATOR CARTRIDGE MOUNTING PROVISION STORAGE ADAPTER NOTE 1 NUMBER PROVISION LIG T Note 5 Note 8 S-82965 142-167 Shelf 169-438...
  • Page 10 FEATURES OF IG FIDELITY & STEREO FM MODELS CABINET SPEAKERS C ASSIS VOICECOIL PART SIZE MODEL STYLE POWER IMPED. COLOR MODEL TYPE NUMBER (In Inches) OUTPUT (In Ohms) CT953DE1 Console Dark Oak 29CT30 FM/AM/Phono 2x25W 49-1094 4-3% (Lift Lid) 49-1162 2-Horn 49-1171 2-12...
  • Page 11 FEATURES OF IG FIDELITY & STEREO FM MODELS OT ER FEATURES RECORD C ANGER POWER REMOTE TAPE RECORD PART STYLUS 45 RPM SPEAKER CARTRIDGE INDICATOR MOUNTING PROVISION STORAGE NUMBER NOTE 1 ADAPTER PROVISION LIG T 169-434 142-167 S-82965 Built-In Note 4 Shelf S-82621 C632...
  • Page 12 Model C635 - Cartridge Tape Player, Model A636 - Cassette Tape Player/Recorder. 9. One pair of Model C9015W Extension Speakers may be used with any Zenith stereo model (not exceeding 15 watts-EIA-per channel) which have external speaker terminals (see notes 4 and 5 above).

  • Page 13: Base Plate

    RECORD CHANGER FEATURES TURNTABLE BASE PLATE PART NO.MFG. Light Beige Tree Bark Brown 169-361 (VM) Dark Brown Bronze Gold 169-364 Tree Bark Brown Light Beige (VM) 169-366 Yellow (BSR) Off White 169-373 Dark Green Off White 169-374 (BSR) Gray Off White 169-375 (BSR) Light Gray and Metal...
  • Page 14 For theory and operation, of circuits not covered in this man ­ There are certain minimum voltages necessary for proper ual, refer to Service Manuals HF 8 (Zenith Part No. 923-558), stereo FM reception. To help determine if there is sufficient 9 (Zenith Part No.
  • Page 15 CIRCUIT BOARD COMPONENT IDENTIFICATION may be noted when tuning between Frequency Modulation As a special feature to aid the Service Technician, Zenith has stations. This is normal, and will disappear as the station is identified the location of components which are mounted on tuned in.

  • Page 16: Resistance Measurements

    Connect to Ratio Detector Test Point “ H ” . An open or damaged section of circuit board wiring foil can be repaired b»y soldering a short jumper wire across the points to Connect to the last FM IF Test Point “ G ” . be connected.
  • Page 17 □ ■ £ < < < — G> 8 ‘ v> & < < < o r — □ < < 3 0! ) CJ < o> □ r — r —...
  • Page 18 Using the Zenith FM multiplex signal generator, the multiplex megahertz must be on the curve at the reference line. portion of Zenith or any FM multiplex receiver can be aligned, megahertz and 0.9 megahertz must be at the lower and upper but first before any attempt is made to do this it is necessary turn of the S curve respectively.

  • Page 19: Trouble-S Ooting

    in this manner the multiplex alignment would then be the best portion, the multiplex generator can be used as an excellent that could possibily be obtained and separation would be the signal tracing device to determine if the multiplex section of maximum for this receiver.
  • Page 20 NOTES...
  • Page 21 NOTES...

  • Page 22: Parts List

    (2 Used on Ea. 800-362) -AM Antenna Trimmer-AM Detector Trimmer-AM 2 -430 Transistor - Pre-Amplifier (2 Req.) Detector Tuning-AM Oscillator Trimmer-AM Oscil ­ 2 -433 Transistor - Pre-Driver (2 Req.) lator Tuning *Dp.nnfp.s narfs not nrevinuslv used in Zenith receivers.
  • Page 23 00K Ohm Resistor - /2W. 5% (2 Used on P.C. 95-2858 Input Transformer 9KHz Board - Audio Amp.) 00-249 Pilot Light Bulb (2 Req.) 63- 873 20KOhm Resistor - /2W. 0% 00-507 Stereo Indicator & Wire *Denotes parts not previously used in Zenith receivers.
  • Page 24 .0022 MF Ceramic Disc Capacitor - + 0% 500V. 58-338 Dial Pointer Blade (3 Req.) *59- 098 63- 70 0 Ohm Resistor - /2W. 0% (3 Req.) 22-2428 .8 PF Gimmick Capacitor - 500V. *Denotes parts not previously used in Zenith receivers.
  • Page 25 Field Effect Transistor (N Channel) 63-8977 Bias Control - IK Ohm 30% /4W. (2 used on P.C. Tuning Meter 22-66 Board - Audio Amp.) * 26- 52 Heat Sink 63-8996 Balance Control - 250K Ohm *Denotes parts not previously used in Zenith receivers.
  • Page 26 390 PF Polystyrene Capacitor - 25 V. *22-5972 680K Ohm Resistor - /2W. 0% 63- 904 50 MF Electrolytic Capacitor - 25 V. (2 Req.) 22-5986 .5 Megohm Resistor - /2W. 0% (4 Req.) 63- 9 8 ♦Denotes parts not previously used in Zenith receivers.
  • Page 27 (2 Req.) 00-249 Indicator Lamp, Pilot Light Bult (3 Req.) 22- 4 .0047 MF Disc Capacitor - 500V. (3 Req.) 03-23 Germanium Diode (6 Req.) 22-2428 .8 PF Gimmick Capacitor - 500V. *Denotes parts not previuosly used in Zenith receivers.
  • Page 28 Idler Pulley Spring (Part of S-7750 ) 6 -222 Idler Pulley (Part of S-7750 , S-85563, S-7550 , 80-2 43 Cord Tension Spring S-85564 & 2 Part of S-89890) *82- 95 Ground Strap ♦Denotes parts not previously used in Zenith receivers.

  • Page 29: Cabinet Components

    964- 6580 Eyelet, Pivot (2 Req.) ♦ 49-426 Ferrite Core, Antenna Rod (Part of S-88463) 964- 7 70 Amp. Terminal - .205 Flat 88- 40 Retaining Ring *964- 73 0 Bumpers (4 Req.) ♦Denotes parts not previously used in Zenith receivers.
  • Page 30 Inside Changer Compartment) *964-25775 6 x9 PM Speaker - 8 Ohm (2 Req.) 5.50 964-20622 Terminal - Male (7 Req.) *964-25777 Changer Insert 964-20623 Terminal - Female (7 Req.) *964-2578 Bracket (2 Req.) ♦Denotes parts not previously used in Zenith receivers.
  • Page 31 *9 0-8 IB Grille Cloth *9 2-594B 3. x 20 Screw *9 2-595B . 3. x 3 Screw ( 0 Used on 802- 0B) *9 2-596B 3x 0 Screw (2 Used on 883-28 3B) *Denotes parts not previously used in Zenith receivers.
  • Page 32 SPEAKER WIRING SC EMATICS...
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  • Page 47 29CT20 AND 29CT21 - C ASSIS LAYOUT...
  • Page 48 LEGEND C ASSIS 29CT20 ITEM PART ITEM PART DESCRIPTION DESCRIPTION NUMBER NUMBER R226 681852 39K O M FM ANT TRIMMER FM ANT TUNING R227 681855 47K O M 39KO M FM DETECTOR TRIMMER R228 681852 R229 681873 120K O M FM DETECTOR TUNING FM OSC.
  • Page 49 29CT20 - PREAMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE 29CT20 - POWER AMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE...
  • Page 50 LEGEND C ASSIS 29CT21 ITEM PART ITEM PART DESCRIPTION DESCRIPTION NUMBER NUMBER FM ANT TRIMMER 'R229 63-1873 120K O M FM ANT TUNING R230 63-1859 56K O M FM DETECTOR TRIMMER R231 63-1820 6.8K O M FM DETECTOR TUNING IR232 680 O M 63-1778 FM OSC.
  • Page 51 29CT21 - PREAMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE 29CT21 - POWER AMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE...
  • Page 52 29CT20 AND 29CT21 AND 29CT21Z1 - RF/IF - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE...
  • Page 53 29CT21Z1 - C ASSIS LAYOUT...
  • Page 54 LEGEND C ASSIS 29CT21Z1 ITEM PART ITEM PART DESCRIPTION DESCRIPTION NUMBER NUMBER FM ANT TRIMMER R221 63-1827 10KO M 63-1778 680 O M FM ANT TUNING R222 FM DETECTOR TRIMMER R223 63-1904 680K O M FM DETECTOR TUNING R224 63-1898 470KO M20% FM OSC.
  • Page 55 29CT21Z1 - PREAMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SIDE 29CT21 - POWER AMP - C ASSIS WIRING AND COMPONENTS VIEWED FROM FOIL SC DE...
  • Page 56 29CT30 - SC EMATIC...
  • Page 57 LEGEND C ASSIS 29CT30 ITEM PART ITEM PART DESCRIPTION DESCRIPTION NUMBER NUMBER R219 63-1841 22K O M FMANT TRIMMER R220 63-1785 1KO M FM ANT TUNING R221 63-1834 15KO M FM DETECTOR TRIMMER R222 63-1785 IK O M FM DETECTOR TUNING R223 63-1904 680K O M...
  • Page 58 29CT30 - C ASSIS LAYOUT...
  • Page 59 •*...
  • Page 60 ZENIT RADIO CORPORATION 1900 N. AUSTIN AVENUE C ICAGO. ILLINOIS 00639 SPECIFICATIONS SUBJECT TO C ANGE WIT OUT NOTICE 923-653 HF24 RR 12/71 30M PRINTED TN U.S.A.

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