McIntosh MC225 Service Manual

Table 1. MC225 VOLTAGE AND RESISTANCE CHART
(Schematic No. SC126-167A)
Tube
12AX7
(VI)
12AU7
(V2 or V3)
12BH7
(V4 or V5)
7591
(V6, V7, V8, or V9)
Pin No.
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
DC Volts
115
0
1
FIL
FIL
115
0
1
FIL
295
115
121
FIL
FIL
295
100
121
FIL
285
25
39
FIL
FIL
285
25
39
FIL
FIL
390
390
0.8
-21
FIL
390
Resistance in
Ohms, Unit Off
180K
1M
3.3K
0
0
180K
1M
3.3K
0
27K*
180K
18K
0
0
30K*
2.4M
18K
0
22K*
220K
4.7K
0
0
22K*
220K
4.7K
0
0
62*
130*
40
180K
0
130*
This Resistance measured to positive side of B+ rectifier SR2. Warning:
Discharge filter condensers before making measurements.
A high resistance VTVM is used for all measurements, voltages and resis-
tances are to ground except as noted.

McIntosh MC225 Specifications

General

Power Output	25 watts per channel
Total Harmonic Distortion	0.5% at rated output
Input Impedance	250k ohms
Output Load Impedance	4, 8, or 16 ohms
Frequency Response	20Hz to 20kHz (+0 -0.5dB)
Signal to Noise Ratio	90dB