McIntosh MA-6900 Service manual

INTEGRATED AMPLIFIER

CONTENTS

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

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

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

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

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

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

Main Schematic and PCB.................................... 9 - 18

Balanced Schematic and PCB.............................. 12, 18

Heatsink Schematic and PCB ............................. 19 - 20

SERVICE MANUAL

Capacitor Schematic and PCB ........................... 21 - 22

Control Schematic and PCB .............................. 23 - 26

Lamp Schematic and PCB ................................. 25 - 26

Tone Schematic and PCB .................................. 27 - 31

Keyboard Schematic and PCB ........................... 30 - 32

Parts List ............................................................ 33 - 36

Exploded Views and Parts Lists .......................... 37 - 40

Repacking Instruction .............................................. 41

PERFORMANCE SPECIFICATIONS

Power Output

Minimum sine wave continuous average power output per channel, all channels operating is: 200 watts into 2 ohm load 200 watts into 4 ohm load 200 watts into 8 ohm load

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% for 2, 4 or 8 ohm loads

Dynamic Headroom

2.4dB

Frequency Response

+0, -0.5dB from 20Hz to 20,000Hz +0, -3dB from 10Hz to 100,000Hz

Sensitivity

Phono, 2.5mV for 2.5V rated output (0.5mV IHF) High Level, 250mV for 2.5V rated output (50mV IHF) Power Amplifier Input, 2.5V for rated output

Signal To Noise Ratio (A Weighted)

90dB (84dB IHF) below 10mV input, Phono Input 100dB (90dB IHF) below rated output, High Level 110dB below rated output, Power Amplifier

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% for 2, 4 or 8 ohm loads

Input Impedance

Phono, 47k ohms, 65pF High Level, 22k ohms

Maximum Input Signal

Phono, 90mV High Level, 8V

Preamplifier Maximum Voltage Output

Phono, 8V at tape output High Level, 8V at tape output Main Out, 8V at preamp output

Voltage Gain

High Level to T ape: 0dB High Level to Main: 20dB

Wide Band Damping Factor

Greater than 40

Power Requirements

100 Volts, ~ 50/60Hz at 4.8 amps 110 Volts, ~ 50/60Hz at 4.4 amps 120 Volts, ~ 50/60Hz at 4.2 amps 220 Volts, ~ 50/60Hz at 2.0 amps 230 Volts, ~ 50/60Hz at 2.0 amps 240 Volts, ~ 50/60Hz at 2.0 amps

Note: Refer to the rear panel of the MA6900 for the correct voltage.

Overall Dimensions

Front Panel: 17-1/2 inches (44.45cm) wide, 7-1/8 inches (18.10cm) high. Depth behind front mounting panel is 16-1/2 inches (41.91cm). Clearance required in front of the Front Panel is 1 inch (2.54cm) for knobs.

Weight

74.5 pounds (33.8 Kg) net, 92.5 pounds (41.7 Kg) in shipping carton

1. The heavy lines 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).

NOTES

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.