McIntosh MI350 Power Amplifier Service Information.pdf
SERVICE INFORMATION McIntosh laboratory inc. 2 chambers street Binghamton, new york ELECTRICAL SPECIFICATIONS POWER OUTPUT FREQUENCY RESPONSE HARMONIC DISTORTION INTERMODULATION DISTORTION NOISE AND HUM LEVEL 350 watts continuous at 8, 16, 50, 6ip ohms, 325 watts continuous at 4 ohms, 300 watts continuous at 1 ohm. 20Hz to 20kHz +0, -0.5dB at 350 watts output. 1Hz to 70kHz +0, -3dB at 1 watt output. Less than 0.1$% at rated output or less, 20Hz to 20kHz. Less than 0.15 -95dB INPUT LEVEL OUTPUT IMPEDANCE OUTPUT VOLTAGES AC POWER INPUT 1.1 volt 1, ip, 8, 16, 50, and 61p ohms. 17.3, 35.8, 53, 75, 132, 150 volts. 117/125 volts, 50/6OHZ, lp00-900 watts. SCHEMATIC NOTES 1. Unless otherwise specified, resistance values are in ohms, 1/2 watts, and 10 tolerance. Capacitance values smaller than 1 are in microfarads (|jlF); values greater than 1 are in picofarads (pF). Inductors, unless otherwise specified, are in microhenries (p.H). 2. The terminal numbering of rotary switches and printed circuit board wires is for reference only. 3. All voltages are measured under the following conditions: Use of an 11 megohm input impedance VTVM voltmeter. All voltages +10/ with respect to chassis ground. No signal at input terminals. AC input at 117 volts, 50/60 cycles. Front panel controls at: gain meter range power output range fully counterclockwise off on fully counterclockwise ip. In units with serial Numbers below 10R51p: LI through L8 are not used; Rlllp is 820ft $% 1/2W; and C207D is used. 5 C6 is used in early units THERMAL PROTECTOR GRV/WHT TO AMPLIFIER SECTION M METER RANGE * - ROTORS ARE INTERCONNECTED METER SECTION Ml-350 154-372 I 600 A INPUT I2AX7/ECC83 I2AX7/ECC83 6DJ8/ECC88 6 (INPUT TRANSFORMER) KM (SUB-SONIC FILTER) AMPLIFIER SECTION PRINTED CIRCUIT BOARD 043- I |gain | REAR I ( CHASSIS INPUTS 2( FRONT l< PANEL INPUTS 2< ,S; ZS.ZV .22 /Z50V 56K p - 2 a tr * u. . j T INPUT TRANSFORMER T I (OPTIONAL) 1 GND M N TO METER SECTION AMPLIFIER SECTION Ml - 350 154-345 REPLACEMENT PARTS D202 Si. rectifier All parte not listed are common items obtain able from radio parts jobbers. Replacement parts may be obtained when ordered by PART NUMBER from: McIntosh Laboratory Inc. Customer Service Department 2 Chambers Street Binghamton, New York: 13903 (telephone 607-723-3512) CAPACITORS Symbol Number Description Part Number Cl Mylar .lpF 250V 10$ 064-038 C2 Mylar . 22pF 250V 064-043 C3 Elect. 12pF 250V 066-046 c4 Mylar . 22pF 25 ov 064-043 c8 Elect. 12pF 250V 066-046 CIO Elect. lOOpF 25V NP 066-115 Cll,12 Mylar 47pF 400V 064-051 CIS,16 Mylar . 22pF 630V 064-052 ci7,i8 Elect. 50pF 50V 066-014 C19,20 Elect. 12pF 250V 066-046 C21.22 Elect. 8pF 600V 066-118 C101 Mylar 47pF 25 ov 064-045 C102 Elect. 330pF 3V 066-105 C103 Elect. lOOpF 12V 066-018 C104 Elect. 20pF 20 V 066-121 C201 Elect. lOOpF 25V 066-124 C203 Elect. 700pF 275V 066-117 C204 Elect. 700pF 275V 066-117 C205 Elect. 700pF 275V 066-117 C206 Elect. 700pF 275V 066-117 C207 Elect. 100/30/30/30PF 066-116 450/300/250/250V DIODES D1 Si. rectifier 070-031 D2 Zener diode 10V 070-024 D3 Si. signal diode 070-022 D101 Ge. signal diode 070-003 D102 Ge signal diode 070-003 D103 Ge signal diode 070-003 D104 Si. signal diode 070-022 D105 Si. rectifier 070-030 D201 Si. rectifier 070-043 070-043 D203 Si. rectifier 070-043 D204 Si. rectifier 070-043 D205 Si. rectifier 070-031 D206 Zener diode 180V 070-037 CIRCUIT BREAKERS CB201 Power on-off 088-004 FUSES F201 Fuse 10 ampere Slo-Blo 089-018 CHOKES LI, 2 Choke 1.2pH 122-011 L3,4 Choke 1.2pH 122-011 L5,6 Choke 1.2pH 122-011 L7,8 Choke 1.2pH 122-011 L201 Filter choke 122-061 METERS M101 Meter 124-014 TRANSISTORS Q101 Si. NPN transistor 132-057 Q102 Si. NPN transistor 132-057 Q201 Si. NPN transistor 132-059 POTENTIOMETERS R3 Gain control 134-192 R37.38 Bias adjust 134-176 R45.46 Bias adjust 134-176 R53.54 Bias adjust 134-176 R6l,62 Bias adjust 134-176 R101 Volt, range calibration 134-197 R113 DB range calibration 134-197 R210 Hum balance 134-086 RESISTORS R8 Wirewound 10K 5$ 5w 139-051 R15,16 Composition 100K 1$ 1/2W 136-468 R28,29 Composition 39K 1$ 2W 136-467 R31.32 Wirewound 10 K 1$ 5w 139-052 R39,4 Wirewound 200 ohm 10$ 2W 139-069 R43,44 Wirewound 5 ohm 5$ 5w 139-068 R47.48 Wirewound 200 ohm 10$ 2W 139-069 R5i,52 Wirewound 5 ohm 5$ 5w 139-068 Output range knob Meter bezel 090-079 020-022 R55,56 Wirewound 200 ohm 10% 2W 139-069 R59,6o Wirewound 5 ohm $% 5W 139-068 R63.64 Wirewound 200 ohm 10% 2W 139-069 R67,68 Wirewound 12K 10% 5W 139-053 R69.70 Wirewound 5 ohm 5$ 5W 139-068 R102 Wirewound 18k $% 5W 139-062 RIO 9 Wirewound 12K % 5W 139-063 Rill). Wirewound 820K $% 2W 139-072 R201 Wirewound 1.5k 10% 20W 139-061). R202 Wirewound 30 ohm 10% 5W 139-067 R203 Thermistor 144-006 R201). Wirewound 30 ohm 10% 5W 139-067 SWITCHES SI Sub-sonic filter switch 148-002 S2 Output impedance switch ll).6-113 S101 Meter range switch 146-112 S201 Line voltage switch 149-006 S202 Thermal cut-out 153-010 TRANSFORMERS T1 Input transformer 159-001 T2 Output transformer 043-766 T201 Power trans (high voltage) 043-765 T202 Power trans (low voltage) 043-764 TUBES VI,5 6LQ6/6JE6B 165-059 V2,6 6LQ6/6JE6B 165-059 V3,7 6LQ.6/6JE6B 165-059 VI)., 8 6LQ6/6JE6B 165-059 V9 12AX7/ECC83 165-019 V10 12AX7/ECC83 165-019 Vll 6DJ8/ECC88 165-056 V12 6CG7/6FQ7 165-057 V13 6DJ8/ECC88 165-056 Vll). 6BL7GTA 165-058 FRONT PANEL !a SERVICE BULLETIN ELIMINATION OF SELF TURN-OFF MODEL: MC 3500/MI - 350 Power Amplifier PURPOSE OF MODIFICATION: To prevent amplifier from turning off at maximum output. WHAT UNITS ARE AFFECTED: MC 3500 Serial No. 10N01 & Above MI-350 Serial No. 10R01 & Above WHEN MODIFICATION SHOULD BE MADE: Any time any service is performed, or if customer complains that the amplifier will not remain on. McIntosh modification kit no.: no kit. PARTS REQUIRED: QUANT ITY 1 PROCEDURE: Step 1 Remove bottom cover. Step 2 Add resistor in parallel with capacitor C201 (shown at circuit breaker on schematic). Step 3 Replace bottom cover. PART NUMBER DESCRIPTION 139-069 200ft 2W wirewound resistor 038-558
