McIntosh MAC 1500 Service Manual

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MAC 1500 STEREO RECEIVER INTRODUCTION All Mclntosh tuners are carefully aligned and tested at the factory using the finest available test equipment. All Mclntosh tuners will meet their published specifica- tions when shipped from the factory. After extensive operation, especially when tubes have been replaced, it may be desirable to realign the timer circuits for best performance. This manual gives complete information on the circuit realignment procedure for the MAC 1500 receiver. The test equipment listed below (or its equivalent) is necessary to properly align a MAC 1500. The accuracy of the alignment will be directly related to the accuracy and calibration of the test equipment used. FM Signal Generator (Measurements 210A or equivalent) VTVM Multiplex Generator (RCA WR51A or equivalent) 10.7 MC Generator (Preferably crystal controlled) Oscilloscope (Hewlett -Packard 120B or equivalent) Harmonic Distortion Analyzer (Hewlett-Packard 330B or equivalent) If the necessary test equipment is not available, alignment should not be attempted. You may contact the Mclntosh Customer Service Department for additional information. Customer Service Mclntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York Our telephone number is 723-5491 The direct dial area code is 607 1

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MAC 1500 STEPS 1 2 3 4 5 6 7 8 9 10 11 2 TUNER DIAL SETTING Point of no interference and no signal SAME SAME 105MC 90MC 105MC 90MC 90MC 105MC and 90MC 90MC 90MC SIGNAL GENERATOR FREQ. 10.7MC SAME SAME 105MC 90MC 105MC 90MC 90MC 105MC and 90MC 90MC 90MC COUPLING Through external .01 MFD capacitor to mixer grid (pin 4 or 6DS4, V2) SAME SAME 300 ohm antenna terminals with matching network* SAME SAME SAME SAME SAME SAME SAME MODULATION cw SAME SAME 400 cycles 75KC deviation (100% modulation) SAME SAME SAME SAME 50 cps 150KC deviation Approx. 5 microvolts at antenna terminals 400 cycles 75KC deviation (100% modulation) SAME INDICATOR TYPE VTVM SAME SAME CONNECTED TO TP#1 Pin 1 of T4 TP#2 VTVM connected to TP#2 and. scope connected to L or R tape output SAME SAME SAME VTVM connected to TP#2; scope and distortion analyzer connected to L or R tape output See note ** at bottom of page Scope connected to L or R tape output VTVM connected to TP#1; scope and distortion analyzer connected to L or R tape output

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MAC 1500 TOP and BOTTOM VIEWS V 15 V 14 V13 BIAS ADJUST CONTROLS V12 V3 V4 OUTPUT TRANSFORMERS POWER TRANSFORMER MIXER LEFT AND RIGHT PRE AMP PRINTED CIRCUIT BOARDS TRIMMER RF 3RD IF TRANSFORMER V 4 MUTE ADJUST CONTROL 2ND IF TRANSFORMER 1ST IF TRANSFORMER INJECT 10.7 MC SIGNAL HERE MIXER COIL 15 TUNING CONDENSER COVER ANTENNA COIL V14 V15 V12 V13 V1 TRIMMER COIL V2 V10 V9 V11 LEFT RIGHT OSCILLATOR COIL TRIMMER 6EA8 (V7) 12AU7 (V8) COIL RF COIL LOW PASS FILTER ANTENNA COIL 67 KC FILTER 38 KC TRANSFORMER 19 KC TRANSFORMER MPX INPUT (WHITE WIRE; Q7 Q5 Q8 Q6 19KC PHASE COIL DISCRIMINATOR TRANSFORMER V5 Q3 Q4 Q2 2.2K V6 4TH IF TRANSFORMER