McIntosh C22 Preamp Service Information.pdf
Hfrlntosb c 22 SERVICE INFORMATION STARTING WITH SERIAL NO. 10A01 r McIntosh laboratory inc. 2 chambers street Binghamton, new york ELECTRICAL SPECIFICATIONS Frequency Response +0.5 to -0.5 dB, 20Hz to 20,000Hz Distortion Less than 0.2% at 10 volts output Less than 0.02% at 3 volts output Input Sensitivity (phono 1, phono 2, tape head) 2 millivolts for 2.5 volts output at 1kHz Input Sensitivity (Microphone) 2.5 millivolts for 2.5 volts output Input Sensitivity (aux, tape, tuner) 0.25 volts for 2.5 volts output Hum And Noise (phono 1, phono 2, tape head) 74- dB below 10 millivolts input Hum And Noise (aux, tape, tuner) 85 dB below rated output Output (main) 2.5 volts with rated input. Up to 10 volts can be developed without distortion. Output (tape) 0.25 volts with rated input. Phono input signal of 10 millivolts produces 1.25 volts output. Output (L values greater than 1 are in picofarads (pF). i Resistors marked with - are 1/4.W, The terminal numbering of rotary switches and printed circuit board wires is for reference only. All voltages are measured under the following condi tions : 1. Use of an 11 megohm input impedance VTVM 2. All voltages _+10$ with respect to ground 3* AC input at 117 volts, 0/60 cycles L* No signal at input terminals Front panel controls at normal positions VI 8 V3A l I2A X7 jl2AX7 - the original selenium rectifier in the C 11 and C 22 is replaced by four (4) silicon rectifiers. The rectifiers are McIntosh part number 070-014, or any 50 PIV 750 MA rectifiers. PROCEDURE: The selenium rectifier is replaced by a terminal strip and the new silicon rectifiers are installed as shown in the following diagrams. NOTE THAT TERMINAL STRIPS ARE REQUIRED C 8, C 11, C 22 DATE: NOVEMBER, 1965 MODEL NUMBER: C 22 MODIFICATION: Replacement information for circuit modules. PROCEDURE: C 22s built before 1965 used circuit modules made by Erie Electronics. In 1965 we changed to Sprague Electric Co. The Sprague modules are electrically equivalent to the Erie modules but differ mechanically. The newer Sprague modules are used for replacement when servicing early C 22 units. The attached schematic shows the lead connections for both the Erie modules (PC 120-161, PC 120-133, PC 120-132, PC 120-134, PC 120-138, and PC 120-160) and the Sprague modules (130-015, 130-016, 130-017, 130- 018, 130-019, 130-020, and 130-021.) Follow the schematic to replace an Erie module with a Sprague module. NOTE: The Sprague 130-015 replaces 2 each PC 120-161 units, and a Sprague 130-018 plus a 130-019 replaces one PC 120-134. PILOT LAMP REPLACEMENT To insure long life of festoon pilot lamps, always replace them in pairs in the C22. The two lamps are connected in series. As the lamps age their resistance increases. If only one lamp is replaced the older lamp will have higher resistance than the new lamp. This will cause more voltage to be present across the older lamp. The higher voltage will cause the older lamp to burn out more quickly than it otherwise would. McIntosh festoon pilot lamps are designated part number 058-011. Specially-selected lamps are available for the C22. When ordering lamps for the C22, please request by part number 058-011 GREEN DOT. Use only the GREEN DOT lamp in the C22. Do not use them in any other product. Al Hyle, Service Manager
