McIntosh C22 Preamp Schematic.pdf
NOTES I. UNITS WITH SERIAL NUMBERS BELOW USE TWO PC 120-161C MODULES INSTEAD OF ONE PC 144-208. THE PC 120-161 CIRCUIT IS AS ILLUSTRATED BELOW. -AAA/- p fs i, ; 2 UNITS With serial numbers below use two PC 120 - 13 3 B INSTEAD OF TWO PCI44-202. MODULES. THEY BOTH CONNECT IN THE SAME MANNER. 3. UNITS WITH SERIAL NUMBERS BELOW USE TWO PC 120- 132 B INSTEAD OF TWO PC144-205 MODULES. THE PCI20-I32B CIRCUIT IS AS ILLUSTRATED BELOW. PCI20-I34A INSTEAD OF PCI44-204 AND PC144-204 MODULES. THE PCI20-I34A CIRCUIT IS AS ILLUSTRATED BELOW. UNITS WITH SERIAL NUMBERS BELOW USE TWO PC 120-136 INSTEAD OF TWO PCI44-206 MODULES. THEY BOTH CONNECT IN THE SAME MANNER. 8. UNITS WITH SERIAL NUMBERS BELOW USE TWO PC I20-160C INSTEAD OF TWO PC 144-207 MODULES. THE PCI20-I60C CIRCUIT IS AS ILLUSTRATED BELOW. 7. RESISTORS MARKED ARE 1/4 W 20%. 8. UNLESS OTHERWISE SPECIFIED ALL RESISTORS ARE IN OHMS 1/2 W 10%. ALL CAPACITORS ARE IN MFD. 9. ALL VOLTAGES MEASURED UNDER THE FOLLOWING CONDITIONS. USE OF II MEGOHMS INPUT IMPEDANCE VTVM ALL VOLTAGES -10% WITH RESPECT TO GROUND AC INPUT AT 117 V. 30-60 CPS FRONT PANEL CONTROLS AT BALANCE - FLAT INPUT SELECTOR-AUX MODE SELECTOR- STEREO VOLUME- MAX TONE CONTROLS-FLAT COMP- RIAA TAPE-NORMAL TAPE JACKS RECORD FILTERS-FLAT LOUDNESS - NORMAL | | PCI44-Z04 I j |_NOTE 4_| BASS jrnQZBI LEFT OUTPUT ) L + R OUTPUT RIGHT OUTPUT imsas HBfai SR 3 X 1 1 FROM POWER AMP. 1 -X LI J* I 1 POWER SUPPLY 1 117 V | I TO SPEAKERS J 50/60 CPS JC ASE SWITCH 1 LAST R - 75 LAST C- 36 schematic, C22 1 HK jnto 5 HuBONArONT INC. 1 r“ K. J*,r VO “6-29.63 SC I44E2I6 MODEL NUMBER: C 8, C 11, C 22 DATE: APRIL 1965 MODIFICATION: Replace the selenium rectifier with silicon rectifiers. These silicon rectifiers have much longer life. DESCRIPTION: The original selenium rectifier in the C 8 is replaced by two (2) silicon rectifiers; 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
