McIntosh MC 40 Service Manual

Page 1

SERVICE INFORMATION

STARTING WITH SERIAL NO. TOOLI

McINTOSH LABORATORY INC.

2 CHAMBERS STREET BINGHAMTON, NEW YORK

01? JW

Page 2

ELECTRICAL SPECIHCAIIONS

Power Output
ho watts continuous

Harmonic Distortion
Less than 0.5% at ho watts output or less, 20Hz
through 20,000Hz

Intermodulation Distortion
Less than 0.5% for any combination of frequencies from
20Hz through 20,000Hz if instantaneous peak power is
below 80 watts

Phase Shift
Less than :8 degrees, 20Hz through 20,000Hz

Frequency Range
At no watts output: +0, -O.1 dB 20Hz through 20,000Hz
+0, -O.5 dB lon through 60,000Hz
At 20 watts output: +0, -1 dB 10Hz through 100kHz

Noise and Hum
90 dB or more below rated output

Output Impedance
4 ohms, 8 ohms, 16 ohms, 125 ohms, 150 ohms, and 600 ohms.
The 600 ohm winding is balanced to ground and center tapped.

Output Voltages
25 volts and 70.? volts

Internal Impedance
Less than 10% of rated load.\impedance

Input
Input finpedance: 250,000 ohms
Input sensitivity: 0.5 volts to 30 volts through gain con-
trol 2.0 volts with gain control turned
fully clockwise

Power Requirements
117 volts AC, 50/60 cps. Uses th watts at ho watts
output; 75 watts at zero signal output.

SCHEMATIC NOTES

1. In units with serial numbers below 511L0, power transformer
T2 is connected as shown in detail "A".

2. In units with serial numbers above h28L7; R26, C2, 018,
& C19 do not appear.

. In units with serial numbers below h28L7, R11 was 27K.

3
h. In units with serial numbers below h28L7, R12 was 30K.
5. In units with serial numbers below 428L7, R27 was 100K.
6

. In units with serial numbers below 428L7, C 20 will not
appear.

7. R18 & R19 are matched to within 1% tolerance.