McIntosh-C20-pre-sm 维修电路原理图.pdf
C20STEREO PREAMPLIFIER(Serial No. 6L700 & above)MAINTENANCEMANUALRadioFans.CN 收音机爱 好者资料库DESCRIPTIONCOMPONENT NO.Switch, Input SelectorSwitch, Bass CompensatorSwitch, Treble CompensatorSwitch, High Frequency Cutoff FilterSwitch, Rumble FilterSwitch, Mode SelectorSwitch, Tape CompareSwitch, Tape JackSwitch, PhaseSilicon Rectifier, 50 PIV at 1.6ATransformer, PowerS1S2S3S4S5S6S7S8S9S1, S2M199ADESCRIPTIONCOMPONENT NO.Filter Capacitor, 20/20/40 MF at 300/350/350VFilter Capacitor, 40/40 MF at 350/350VFilter Capacitor, 1000/1000 MF at 15/15VControl, BassControl, TrebleControl, Loudness (Aural Compensator)Control, Volume 4 Section combined with poweron-off switchControl, BalanceControl, Bass Trim (Lo Bass) on rear panelC102C103C104R1R2R 3R4R5R7 (2 used)Special components used in the C20 are listed below. These compo-nents are designed and built specifically for the C20. They may be pur-chased directly from Customer Service, Mclntosh Laboratory Inc. When youTable 2. SPECIAL COMPONENTS(Schematic No. SC119-201)order parts be sure to give the SCHEMATIC NO. and DESCRIPTION fromTable 2 below, and serial and model number for your amplifier.RadioFans.CN 收音机爱 好者资料库Table 1. C20 VOLTAGE AND RESISTANCE CHART(Schematic No. SC117-201)Tube12AX7(V1)12AX7(V2)12AU7(V3)12AU7(V4)12AX7(V5)12AX7(V6)12AX7(V7)6X4(V8)Pin No.1234567891234567801234567891234567891234567891234567891234567891234567DC VoltsNo. Signal14601.05.6-5.611001.014601.05.6-5.611001,06402.45.6-5.6198621206402.45,6-5.6198621201040.75.6-5.62302229_1040.75.6-5.62002229-25020705.6-5.625020700315 AC6.3 AC0_315 AC335Resistance inOhms Unit Off130K*1M2.2K55360K*56K4K130K*1M2.2K55360K*56K4K_120K*501.8K5514K*1.1M100K120K*501.8K5514K*MM100K330K*110K1.8K559K222K22K330K*110K1.8K5531K*222K22K7K*1M47K557K*1M47K0580_.10560*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 SELECTORBALANCEPHASEH.F. FILTERLOUDNESSINPUT SELECTORBASS COMPENSATORTREBLE COMPENSATORBASSTREBLERUMBLE FILTER,TAPE JACK,TAPE COMPAREVOLUMELOW FREQUENCY TRIMSTEREO00FLATFLATTAPE HD 20TAPE00OUTON, CCW0C20 Schematic(Schematic No. SC117-201)NOTES: (1) THlS SCHEMATIC APPLIES TO C20 PREAMPLIFIERS WITH SERIAL NUMBERS 6L700 AND ABOVE.(2) ALL ROTARY SWITCHES ARE SHOWN IN THE EXTREME COUNTERCLOCKWISE POSlTION.(3) ALL PUSHBUTTON SWITCHES ARE SHOWN IN THE OUT POSITION.(4) RESISTOR VALUES ARE IN OHMS 10%, WATT EXCEPT AS NOTED.(5) CONDENSER VALUES ARE IN MFD FOR NUMBERS LESS THAN ONE, AND IN MMFD FOR NUMBERS GREATER THAN ONE.(6) IN SOME UNITS C104 MAY BE FOUND AS TWO SEPARATE 2000 MFD/15V CONDENSERS.(7) A RESISTOR IM SOME UNITS MAY BE USED AT THIS POINT TO ADJUST THE VOLUME CONTROLS TRACKING CHARACTERISTlC.THE VALUE IS MATCHED TO THE PARTICULAR VOLUME CONTROL USED* THESE COMPONENTS HAVE A CLOSE TOLERANCE ON THEIR VALUE, OR HAVE SPECIAL CHARACTERISTICS SUCH ASLOW NOISE OR A SPECIAL RESISTANCE TAPER.LABORATORY INC.2 CHAMBERS STREET, BINGHAMTON, N. Y.Phone-Area Code 607-723-54912M-AA117-201 5-62BE012003Customer ServiceMclntosh Laboratory Inc.2 Chambers StreetBinghamton, New YorkOur telephone number is 723-5491.The direct dial area code is 607.Your C20 will give you many years of pleasant and satisfactoryperformance. If you have any questions concerning the operationor maintenance of this pre-amplifier please contact:
