McIntosh C20 Maintenance Manual page 3

Table 1. C20 VOLTAGE AND RESISTANCE CHART
(Schematic No. SC117-201)
Pin No.
Tube
1
12AX7
2
(V1)
3
4
5
6
7
8
9
1
12AX7
(V2) 2
3
4
5
6
7
8
0
1
12AU7
2
(V3)
3
4
5
6
7
8
9
1
12AU7
2
(V4)
3
4
5
6
7
8
9
12AX7 1
(V5) 2
3
4
5
6
7
8
9
1
12AX7
(V6) 2
3
4
5
6
7
8
9
1
12AX7
2
(V7)
3
4
5
6
7
8
9
6X4 1
2
(V8)
3
4
5
6
7
NOTES: 1. High impedance VTVM is used to measure operating voltages.
2. Resistance measured to grid, (chassis)
3. * Denotes pin 7 of V8 grounded for this test.
4. Control positions for tests are as follows;
MODE SELECTOR
BALANCE
PHASE
H.F. FILTER
LOUDNESS
INPUT SELECTOR
BASS COMPENSATOR
TREBLE COMPENSATOR
BASS
TREBLE
RUMBLE FILTER,
TAPE JACK,
TAPE COMPARE
VOLUME
LOW FREQUENCY TRIM
DC Volts Resistance in
No. Signal Ohms Unit Off
146
130K*
0
1M
2.2K
1.0
5.6 5
-5.6 5
110 360K*
0 56K
1.0 4K
—
—
146
130K*
0
1M
1.0 2.2K
5.6
5
5
-5.6
110 360K*
0 56K
1,0 4K
_
64
120K*
0
<50
2.4
1.8K
5.6 5
-5.6 5
198
14K*
62
1.1M
120
100K
— —
64
120K*
0
<50
2.4
1.8K
5,6
5
-5.6
5
198
14K*
62
MM
120
100K
—
— 330K*
104
0 110K
.7
1.8K
5.6 5
5
-5.6
230 9K
22
222K
29 _ 22K
—
104 330K*
0
110K
.7 1.8K
5.6 5
5
-5.6
200
31K*
22
222K
29
22K
-
—
250 7K*
20 1M
70 47K
5.6 5
-5.6 5
250 7K*
20 1M
70 47K
0 0
_
315 AC 580
—
6.3 AC .1
0 _ _ 0
— 560
315 AC
*
335
STEREO
0
0
FLAT
FLAT
TAPE HD 2
0
TAPE
0
0
OUT
ON, CCW
0