McIntosh MX 115 Operating and installation instructions

SERVICE INFORMATION
STARTING WITH SERIAL NO. AB1 001
r
McIntosh laboratory inc. 2 chambers street binghamton, new york
MX
115

MX 115
ELECTRICAL SPECIFICATIONS
FM TUNER SECT ION
USEABLE SENSITIVITY
SELECT IV ITY
2.5 m i c r ovolts at 100% modulation (+75 kHz
deviation) for 3% total noise and harmonic
distortion IHF.
ADJACENT CHANNEL:
6 dB minimum IHF in "NORMAL" Position.
15 dB minimum IHF in "NARROW" Position.
S IGNAL TO NO ISE RAT 10
ALTERNATE CHANNEL:
70 dB below 100% modulation.
58 dB minimum IHF in "NORMAL" Position.
88 dB minimum IHF in "NARROW" Position.
CAPTURE RAT 10
1.5 d B minimum.
HARMONIC DISTORTION
Mono: Does not exceed 0.3% at 100%
modulation +75 kHz deviation.
Stereo: Does not exceed 0.7%.
SPURIOUS REJECTION
90 dB IHF minimum.
IMAGE REJECTION
95 dB minimum, 88 MHz - 108 MHz.
STEREO SEPARAT ION
AUDIO FREQUENCY RESPONSE
35 dB at 1,000 Hz.
+3 dB 20 Hz to 15,000 Hz with standard
de-emphasis (75 psec.) and 19,000 Hz
pilot filter.
SCA FILTER
50 dB rejection from 67 kHz to 7A kHz.
275 dB per octave slope.
PREAMPL FIER SECTION
FREQUENCY RESPONSE
+0.5 dB, 20 Hz to 20,000 Hz.
DISTORT ION
Less than 0.1% at 2.5 volts 20Hz to 20 kHz.
INPUT SENSITIVITY (phono 1 and phono 2)
2 millivolts for 2.5 volts output at 1 kHz.
INPUT SENSITIVITY (aux, tape)
0.25 volts for 2.5 volts output.
HUM AND NOISE (phono 1 and phono 2)
72 dB below 10 millivolt input.
HUM AND NOISE (aux, tape)
85 dB below rated output.
OUTPUT (main)
2.5 v olts with rated input. Up to 10
volts can be developed without distor¬
tion. FM and AM will produce up to 10
volts output at 100% modulation.
OUTPUT (tape)
0.25 volts with rated input. Phono input
signal of 10 millivolts produces 1.2 volts
output. FM and AM will produce 1.2 volts
output at 100% modulation.
OUTPUT (center channel)
2 volts with rated input to both channels.
BASS CONTROL
-18 dB to +16 dB at 20 Hz.
TREBLE CONTROL
+20 dB to 20,000 Hz.
LF FILTER
Flat or roll off below 50 Hz, down 12 dB
at 20 Hz.
HF FILTER
Flat or roll off above 5000 Hz, down 12 dB
at 20,000 Hz.

TAPE
OUTPUT

MX 115
MPX PRINTED CIRCUIT BOARD 044-291
Step 1 Before stringing unit,
turn pointer adjustment
screw until pulley "A"
is in the center of its
travel.
Step 2 String unit as shown.
Step 3 After stringing unit,
turn tuning shaft until
pointer is as far to
the left as it will go.
Turn the pointer adjust¬
ment screw until the
pointer coincides with
the zero bar of the
logging scale.
TUNING CONDENSER DRUM
Step lj. Turn the tuning knob
making the pointer move
back and forth from one
end of the dial scale
to the other. Return
pointer to the far left DIAL CORD SEQUENCE
POINTER DIAL STRINGING
BLACK (TO TUNING SHAFT )

100 K

MX 115
MX 115
SCHEMATIC NOTES
Unless otherwise specified: Resistance values are in ohms, 1/1+ watt, and 10% tolerance;
capacitance values smaller than 1 are in microfarads (pF); capacitance values greater than
1 are in picofarads (pF); inductors are in microhenries (pH).
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 11 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)
Volume Fully CCW
Mode Stereo
Muting Out
Input Selector FM
Panel Lights Bright
Selectivity Out
f. Voltages shown in rectangles are measured with selectivity switch in the "In" position.

IF CHASSIS
IF PC BOARD 044-277

fn

FM TUNER SECTION
MX 115
154-516

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LEFT
CHANNEL
INPUTS
PHONO 2
PHONO I
AUX.
TAPE OUT
RIGHT
CHANNEL
INPUTS
PHONO 2
PHONO 1
TAPE
AUX.
TAPE OUT

LEFT CHANNEL PREAMP. PRINTED CIRCUIT BOARD 043-991

ttimaa

RIGHT CHANNEL PREAMP. PRINTED CIRCUIT BOARD 043-992

POWER
SUPPLY
/
CENTER
CHANNEL
PRINTED
CIRCUIT
BOARD
044-296
MX 115

T40I
L403

MX 115
MX 115