McIntosh MR 74 Operating and installation instructions

AM/FM
TUNER
STARTING WITH SERIAL NO. ACIOOI
McINTOSH LABORATORY INC.
2 CHAMBERS STREET
BINGHAMTON, NEW YORK
pL UW

MR 74
ELECTRICAL SPECIFICATIONS
AM TUNER SECTION
SENSITIVITY SELECTIVITY, ADJACENT CHANNEL
75uV LHF (external ant.) 35 dB minimum [HF in "NORMAL" Position,
45 dB minimum }HF in "NARROW" Position.
SIGNAL TO NOISE RATIO
IMAGE REJECTION
45 dB THF minimum; 55 dB at 100% modulation.
65 dB minimum 540 kHz - 1600 kHz.
HARMONIC DISTORTION
FREQUENCY RESPONSE
Does not exceed 1% at 30% modulation.
3.5 kHz - 6 dB, "NORMAL" Position.
2.1 kHz - 6 dB, "NARROW" Position.
FM TUNER SECTION
USEABLE SENSITIVITY SELECTIVITY
2.5 microvolts at 100% modulation (475 kHz ADJACENT CHANNEL:
deviation) for 3% total noise and harmonic
distortion [HF. 6 dB minimum [HF jn "NORMAL" Position.
15 dB minimum !HF in "NARROW" Position.
SIGNAL TO NOISE RATIO
ALTERNATE CHANNEL:
70 dB below 1004 modulation.
58 dB minimum IHF jn "NORMAL" Position.
88 dB minimum IHF in "NARROW! Position.
CAPTURE RATIO
1.5 dB minimum. SPURIOUS REJECTION
90 dB IHF minimum.
HARMONIC DISTORTION
Mono: Does not exceed 0.3% at 100% IMAGE REJECTION
modulation +75 kHz deviation.
95 dB minimum, 88 MHz - 108 MHz.
Stereo: Does not exceed 0.7%.
STEREO SEPARATION
AUDIO FREQUENCY RESPONSE
35 dB at 1,000 Hz.
+1 dB 20 Hz to 15,000 Hz with standard
de-emphasis (75 usec.) and 19,000 Hz
pilot filter. SCA FILTER
50 dB rejection from 67 kHz to 74 kHz.
275 dB per octave slope.

88-108 MHz 88-108 MHz 88-108 MHz
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AM ANT 7
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540-1620 kHz 540-1600 kHz
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BIAS
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MR 74 BLOM

FM
SELECTIVITY
DISCRIMI-
SWITCH ye OP 2
FILTER
10.7 MHz
NARROW AMPLITUDE AMPLITUDE
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|
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SIGNAL
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STEREO
FILTERS
VOLUME VARIABLE
CONTROL OUTPUTS
FIXED
QUTPUTS
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MR 74
SCHEMATIC NOTES
Unless otherwise specified: Resistance values are in ohms, 1/4 watt, and 10% tolerance;
capacitance values smaller than 1 are in microfarads (uF); capacitance values greater than
l are in picofarads (pF); inductors are in microhenries (wH).
Printed circuit board components are outlined on the schematics by dotted lines. The circled
numbers around the dotted lines correspond to the numbers on the PC Board layouts.
The heavy lines on the schematics denote the primary signal path.
The terminal numbering of rotary switches is for reference only.
All voltages indicated on the schematics are measured under the following conditions:
a. Use of an 1] megohm input impedance VTVM.
b. All voltages +10% with respect to chassis ground.
c. No signal at input or antenna terminals.
d. AC input at 120 volts, 50/60 Hz.
e. Front panel controls at:
Tuning indicator 100 MHz (no signal)
VoTume Fully CCW
Mode AM (to measure AM section)
FM (to measure FM section)
Muting Out
Stereo filter Out
Panel Lights Bright
Selectivity Normal
f. Voltages shown in rectangles are measured with selectivity switch in the "Narrow!
position.

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