McIntosh MC-252 Service manual

POWER AMPLIFIER

CONTENTS

Performance Specifications ........................................ 2

Notes ......................................................................... 2

Rear Panel .................................................................. 3

Section Location ........................................................ 4

Block Diagram ...................................................... 5 - 6

Interconnection Diagram ...................................... 7 - 8

Heatsink Schematic and PCB ............................. 9 - 14

SERVICE MANUAL

Power Supply Schematic and PCB..................... 15 - 16

Input Schematic and PCB .................................. 17 - 18

Meter/Lighting Schematic and PCB .................... 19 - 21

Meter Led Schematic and PCB .......................... 21 - 22

Parts List ............................................................ 23 - 26

Exploded View and Parts List ............................. 27 - 32

Repacking Instructions ............................................. 33

PERFORMANCE SPECIFICATIONS

Power Output Stereo

250 watts into a 2, 4 or 8 ohm load is the minimum sine
wave continuous average power per channel with both
channels operating

Power Output Mono Bridged

500 watts into a 4, 8 or 16 ohm load is the minimum sine
wave continuous average power output

Power Output Mono Bi-Amp

500 watts into a 1, 2 or 4 ohm load is the minimum sine
wave continuous average power output

Output Load Impedance

Stereo: 2, 4 or 8 ohms
Mono: 1, 2, 4, 8, or 16 ohms

Rated Power Band

20Hz to 20,000Hz

Total Harmonic Distortion

Maximum Total Harmonic Distortion at any power level
from 250 milliwatts to rated power output is 0.005%

Intermodulation Distortion

Maximum Intermodulation Distortion if instantaneous peak
output per channel does not exceed twice the rated output,
for any combination of frequencies from 20Hz to 20,000Hz,
with all channels operating is 0.005%

Dynamic Headroom

2.0dB

Sensitivity

1.6 Volts Unbalanced Input

3.2 Volts Balanced Input

A-Weighted Signal To Noise Ratio

112dB below rated output

Input Impedance

10,000 ohms

Wide Band Damping Factor

Greater than 40

Power Requirements

100 Volts, 50/60Hz at 8 amps
110 Volts, 50/60Hz at 7.2 amps
120 Volts, 50/60Hz at 6.6 amps
220 Volts, 50/60Hz at 3.3 amps
230 Volts, 50/60Hz at 3.3 amps
240 Volts, 50/60Hz at 3.3 amps

Note: Refer to the rear panel of the MC252 for the correct
voltage.

Overall Dimensions

17-1/2 inches (44.45cm) W , 9-7/16 inches (23.97cm) H,
14-3/4 inches (37.5cm) D, including clearance for connec­tors

Weight

94.5 pounds (207.9kg) net, 108.5 pounds (238.7kg) in
shipping carton

Frequency Response

+0, -0.25dB from 20Hz to 20,000Hz
+0, -3dB from 10Hz to 100,000Hz

NOTES

1. The heavy notes on the schematic denote the primary

signal path.

2. Unless otherwise noted, all voltages indicated on the
schematics are measured under the following conditions:
a. AC input at 120 volts, 50/60Hz.
b. All voltages are +/-10% with respect to ground. A

high impedance (10 megaohm) voltmeter must be used.

3 . Unless otherwise specified:

a. Resistor values are in ohms.
b. Capacitor values are microfarads (uF).
c. Inductor values are in microhenries (uH).

4 . On PC board drawings, Square pad indicates:

a. Polarized Capacitors - Positive
b. Diodes - Cathode
c. Others - Pin 1

5. WARNING

Parts marked with the symbol have critical
characteristics. Use only replacement parts recom­mended by the manufacturer.

2

TOP AND REAR PANEL

MC252

3

SECTION LOCATIONS

TOP VIEW WITH COVER REMOVED

BOTTOM VIEW WITH COVER REMOVED

4

BLOCK DIAGRAM

MC252

5 6

1

INTERCONNECT

7 8