McIntosh C20 Preamp Schematic.pdf

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1、RIGHT CHANNEL-1-LEFT CHANNEL TUNER 2 TUNER I TAPE AUX. XTAL 2 - 10 MV 10-70 MV TAPE OUTPUT TAPE COMPARE TUNER 2 TUNER I TAPE AUX. XTAL 2 - 10 MV 10-70 MV TAPE OUTPUT TAPE COMPARE NOTEB : (T) D 0 0 THIS SCHEMATIC APPLIES TO CIO PREAMPLIFIERS WITH SERIAL NUMBERS BLTOO AND ABOVE- ALL ROTARY SWITCHES AR

2、E SHOWN IN THE EXTREME COUNTERCLOCKWISE POSITION. ALL PUSHBUTTON 9WITCHES ARE SHOWN IN THE OUTpOSlTlON. RESISTOR VALUES ARE IN OHMS, 1 lOSL, y WATT EXCEPT AS NOTED- CONDENSER VALUES ARE IN MFD FOR NUMBERS LESS THAN ONE, AND IN MMFD FOR NUMBERS GREATER THAN ONE. IN SOME UNITS C 104 MAY IE FOUND AS TW

3、O SEPARATE 2000 MFDlSV CONDENSERS. A RESISTOR IN SOME UNITS MAY BE USED AT THIS POINT TO ADJUST THE VOLUME CONTROLS TRACKING CHARACTERISTIC. THE VALUE IS MATCHED TO THE PARTICULAR VOLUME CONTROL USED T * THESE COMPONENTS HAVE A CLOSE TOLERANCE ON THEIR VALUE, OR HAVE SPECIAL CHARACTERISTICS SUCH AS

4、LOW NOISE OR A SPECIAL RESISTANCE TAPER. B+2 TREBLE Table 1. C20 VOLTAGE AND RESISTANCE CHART (Schematic No. SC117-201) B + l 117 VOLTS BO - 80 CYCLES 1 MAMIAl SCHEMATIC aaa, ho. Ifrlnlosh u*wuToT iMc. 2 ChamMrt St. Binghamton. N. V. U,00M C20 ou*.e” t1*. *7.i-*l* , D,K VO BA 3.7. 62 SC 117- 201 c“

5、TAR SAC u DC Volts Resistance in Tube Pin No. No. Signal Ohms Unit Off 12AX7 1 146 130K* (VI) 2 0 1M 3 1.0 2.2K 4 5.6 5 5 -5.6 5 6 110 360 K* 7 0 56K 8 1.0 4K 9 12AX7 1 146 130K* (V2) 2 0 1M 3 1.0 2.2K 4 5.6 5 5 -5.6 5 6 110 360 K* 7 0 56K 8 1.0 4K 9 12AU7 1 64 120K* (V3) 2 0 50 3 2.4 1.8K 4 5.6 5 5

6、 -5.6 5 6 198 14K* 7 62 1.1M 8 120 100K 9 - 12AU7 1 64 120K* (V4) 2 0 50 3 2.4 1.8K 4 5.6 5 5 -5.6 5 6 198 14K* 7 62 1.1M 8 120 100K 9 - - 12AX7 1 104 330K* (V5) 2 0 110K 3 .7 1.8K 4 5.6 5 5 -5.6 5 6 230 9K 7 22 222K 8 29 22K 9 12AX7 1 104 330K* (V6) 2 0 110K 3 .7 1.8K 4 5.6 5 5 -5.6 5 6 200 31K* 7

7、22 222K 8 29 22K 9 - 12AX7 1 250 7K* (V7) 2 20 1M 3 70 47K 4 5.6 5 5 -5.6 5 6 250 7K* 7 20 1M 8 70 47K 9 0 0 6X4 1 315 AC 580 (V8) 2 3 6.3 AC .1 4 0 0 6 315 AC 560 7 335 * NOTES: 1. High impedance VTVM is used to measure operating voltages. 2. Resistance measured to gnd. (chassis) 3. * Denotes pin 7

8、 of V8 grounded for this test. 4. Control positions for tests are as follows: MODE SELECTOR STEREO BALANCE 0 PHASE 0 H.F. FILTER FLAT LOUDNESS FLAT INPUT SELECTOR TAPE HD 2 BASS COMPENSATOR 0 TREBLE COMPENSATOR TAPE BASS 0 TREBLE 0 RUMBLE FILTER, ) TAPE JACK, J OUT TAPE COMPARE ) VOLUME ON, CCW LOW FREQUENCY TRIM 0