McIntosh MC-2205 Service manual
MC 22O5
POWER AMPLIFIER
SERVICE INFORMATION
STARTING WITH SERIAL NO. AX1001
MclNTOSH
LABORATORY
INC.
BINGHAMTON,
NEW
YORK
13903
038-980
MC2205
PERFORMANCE LIMITS & RATINGS
PERFORMANCE
Mc Intosh audio power rat i ngs are in accordance with the Federal Trade Commission Regulation of November 4, 1974 concerning power output claims for ampli-
fiers used in home entertainment pro-
ducts.
POWER OUTPUT
STEREO: 200 watts minimum
sine wave continuous average power output, per channel, both channel's operating
into 1 ohm, 2 ohms, 4 ohms,
or 8 ohms load impedance,
which i s:
14.1 volts RMS across 1 ohm
20.0 volts RMS across 2 ohms
28.3 volts RMS across 4 ohms
40.0 volts RMS across 8 ohms
MONO: 400 watts minimum sine
wave continuous average power
output into 0.5 ohm, 1 ohm,
2 ohms, or 4 ohms load impedance, which is:
14.1 volts RMS across 0.5 ohm
20.0 volts RMS across 1 ohm
28.3 volts RMS across 2 ohms
40.0 volts RMS across 4 ohms
MONO: 0.1% maximum harmonic
distortion at any power level from 250 milliwatts to
400 watts from 20 Hz to
20,000 Hz
INTERMODULATION DISTORTION
STEREO: 0.1% maximum if instantaneous
peak power output is 400 watts or less
per channel with both channels operating for any comb i nat ion of frequencies,
20 Hz to
MONO: 0.1% maximum if instantaneous
peak power output is 800 watts or less
for any combination of frequencies,
20 Hz to 20,000 Hz
20,000
Hz
FREQUENCY RESPONSE
(at one watt output)
20 Hz to 20,000 Hz, +0 -0.25 dB
10 Hz to 100,000 Hz +0 -3.0 dB
NOISE AND HUM
95 dB below rated output
RATINGS
OUTPUT VOLTAGES
OUTPUT LOAD IMPEDANCE
STEREO: 1 ohm, 2 ohms, 4 ohms,
and 8 ohms; separate terminals
are provided for each output
MONO: 0.5 ohm, 1 ohm, 2 ohms,
and 4 ohms; obtained by con-
necting together the appro-
priate terminals of both chan-
nel s
RATED POWER BAND
20 Hz to 20,000 Hz
TOTAL HARMONIC DISTORTION
STEREO: 0.1% maximum harmon-
ic distortion at any power
level from 250 milliwatts to
200 watts per channel from
20 Hz to 20,000 Hz, both
channels operat ing
25 volts for distribution lines
DAMPING FACTOR
STEREO: 16 at I ohm output, 50 at 2
ohms output, 30 at 4 ohms output,
16 at 8 ohms output
MONO: 16 at 0.5 ohms, 50 at 1 ohm,
30 at 2 ohms, and 16 at 4 ohms
output
INPUT IMPEDANCE
100,000 ohms
INPUT SENSITIVITY
Switchable: 0.75 volt or 2.5 voltsLevel control provided for higher
input voltages
POWER REQUIREMENTS
120 volts 50/60HZ, 70 to 550 watts.
LEFT INPUT
MC2205
LEFT
SPEAKER
OUTPUT
AC
LINE
RIGHT
SPEAKER
OUTPUT
RIGHT/MONO
INPUT
BLOCK DIAGRAM
LEFT
CHANNEL
OUTPUT
HEADPHONE
LEFT INPUT
RIGHT/MONO
INPUT
INTERCONNECTION
SCHEMATIC NOTES
1.
Unless otherwise
capacitance values sma llr than 1 a re in microfarads (µF) : capacitance values greater
than 1 are in picofarads (pF); inductors are in microhenries (µH).
2 . Printed circuit board components a re ou t1i ned on the schema tics by dotted lines. The
c i rcled numbers on the dotted lines correspond to the numbers on the PC board layouts.
3. The heavy li nes on the schema tics denote the pr ima ry signal path.
4. The terminal number ing of rotary switches is for reference only.
5. All voltages i nd i cated on the schemat i cs a re measu red under the fo11owi ng cond i t i ons;
a. Use of an 11 megohm impedance VTVM.
b. All voltages ± 10% with respect to chassis ground.
c. No signal at input terminals.
d. AC
input
e. Front pane l con t rols at: Rear panel swi tches a t:
Left Gain FULLY CCW Input Level 0.75V
Meter Range WATTS Mode S tereo
Right/Mono Gain FULLY CCW Power Guard Normal
Speakers ON
Power ON
6. Relay K301 shown in energized pos i t i on.
7. Meter adjustments:
Amplifier
into 8 ohm loads with 1 KHz input signal.
a. Set METER RANGE switch to WATTS.
b. Adj us t pot en t i ometer R125 on meter board for a reading of 200 watts on the left meter.
c. Adjust R126 for a reading of 200 watts on the right meter.
d. Set METER RANGE switch to 0 dB
e. Adjust potenti ometer R105 on meter board for a reading of 0 on the DECIBEL scale of the
f. Adjust RI06 for a reading of 0 on the right meter.
must
left meter.
spec
ified:
at 120
volts
be
working properly
Resistance values
AC,
50/60Hz.
to
adjust meters.
are in
ohms,
Ope
1/4
rate
amplifier
watt,
and 10% to
at
full
power
1erance;
MC2205
(40V rms)
8. Power amplifier bias adjustment:
Operate
(approximately 50 watts) or current (approximately O.4 amps). The bias potentiometers R241 &
R242 are located on the power output PC boards.
MC
2205
at 120
volts
line
input
with
no
input
signal.
Measure
the
input
power
a. Turn both bias potentiometers f u l l ccw
b.
Rotate
i
ncrease
bias
then
ad jus
back
tment
off
cw to the
slightly
point
to the
where
point
the
line
where
the
input
line
power
in put
or
current
reaches
begins
its l
owest
va l ue .
c . Repeat step b for each channel independently.
to
MC2205
METER
RANGE
PC
BOARD
044-623
Q242
Q240
Q238
Q230
TOP
BOTTOM
Q236
Q234
Q232
Q228
TOP
BOTTOM
Q235
Q233
Q231
Q227
TOP
BOTTOM
LOCATION OF TRANSISTORS NOT ON PC BOARD
Q241
Q239
Q237
Q229
TOP
BOTTOM
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