McIntosh MI2 Maximum Performance Indicator Schematic 电路图.pdf

SIGNAL STRENGTH CALIBRATION VERTICAL LS R AUDIO POSITION RIGHT GAIN RadioFans.CN 收音机爱 好者资料库 LIFIER + 300 V O PIN 10 TOP DEFLECTION PLATE 13C0 V VZ V 4 A 6U8 MPLIFIER BRN ALL VOLTAGES MEASURED UNDER FOLLOWING CONDITIONS: 1- USE OF II MEGOHMS INPUT IMPEDANCE VTVM VOLTMETER. 2- AL L VOLTAGES +10%, WITH RESPECT TO GROUND 3- A C. INPUT AT 117 V 50-60CPS. 4- NO SIGNAL AT INPUT TERMINALS. 5- MODE SELECTOR AT TEST POSITION UN ESS OTHERWISE SPECIFIED ALL RESISTORS IN OHMS, W, 1C ALL CAPACITORS IN MFD -o BRN YEL o SI SHOWN IN CCW POSITION RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 MODEL NUMBER: Ml 2 DATE: MARCH 1965 MODIFICATION: To eliminate any shape other than a dot when in the TEST position. DESCRIPTION: This modification can be made to all Ml 2s. If a configuration other than a sharply defined spot occurs this indicates possible oscillation in the deflection amplifier. Noise in the deflection amplifier can also cause this condition. Oscillation is caused by coupling between pins 1 and 2 of tubes VI and V3. Noise can be caused by parasitic oscillations of intensity control neon bulbs and by coupling of power line noise into the + 108 volt supply via the filament winding on the power trans former. These modifications have been made to all Ml 3s. PROCEDURE: 1. There are two 10 w resistors under the chassis/ parallel each of these with a 56K 2 w resistor. 2. Remove the neon bulb from the intensity control. 3. Add a 270K 14 w resistor from the center lug of the intensity control to the side lug (at junction of yellow/white wire and 390 K resistor). Add a jumper wire from the center lug of the control to the other lug (junction of orange/white wires). 4. Remove the red/white wire from pin 5 of the 6U8 (6) to pin 1 of the OB 2 (V8). Replace the wire with a 47K 14 w resistor. 5. Add a lOpf capacitor from pin 2 to pin 6 of tubes VI and V3. Bend the tube socket of pins of tubes VI and V3 so that pin 1 is as far away from pin 2 as pos sible. Dress the leads connecting to these pins for maximum separation. MODEL NUMBER: Ml 2 DATE: MARCH 1965 MODIFICATION: To eliminate any shape other than a dot when in the TEST position. DESCRIPTION: This modification can be made to all Ml 2s. If a configuration other than a sharply defined spot occurs this indicates possible oscillation in the deflection amplifier. Noise in the deflection amplifier can also cause this condition. Oscillation is caused by coupling between pins 1 and 2 of tubes VI and V3. Noise can be caused by parasitic oscillations of intensity control neon bulbs and by coupling of power line noise into the + 108 volt supply via the filament winding on the power trans former. These modifications have been made to all Ml 3s. PROCEDURE: 1. There are two 10 w resistors under the chassis, parallel each of these with a 56K 2 w resistor. 2. Remove the neon bulb from the intensity control. 3. Add a 270K I/2 w resistor from the center lug of the intensity control to the side lug (at junction of yellow/white wire and 390 K resistor). Add a jumper wire from the center lug of the control to the other lug (junction of orange/white wires). 4. Remove the red/white wire from pin 5 of the 6U8 (6) to pin 1 of the OB 2 (V8). Replace the wire with a 47K Vi w resistor. 5. Add a lOpf capacitor from pin 2 to pin 6 of tubes VI and V3. Bend the tube socket of pins of tubes VI and V3 so that pin 1 is as far away from pin 2 as pos sible. Dress the leads connecting to these pins for maximum separation. POWER SUPPLY C.R T. CIRCUIT PRODUCT: MI-2/MI-3 MODIFICATION: CIRCUIT CHANGE TO PREVENT POWER TRANSFORMER FAILURE. DESCRIPTION: Power transformers have failed in some M1-2/M1-3 units due to intermittent shorts in the 6W4 HV rectifier tube. These shorts are caused by cathode flaking in the 6W4. The problem can be eliminated by replacing the 6W4 with a 3000 volt 3MA semiconductor rectifier. This modification reduces the amount of heat generated within the MI-2/MI-3 and increases the life and reliability of the unit. PROCEDURE: 1. Remove the MI-2/MI-3 top cover. Remove the 6W4 tube and place an octal plug (Part #127-006) in the socket. 2. Remove the MI-2/MI-3 bottom cover. Cut and remove the jumper wire connecting pin 8 to pin 3 on the 6W4 socket. Connect the 3000 PIV rectifier (Part #070-026) to pin 5 and pin 3 of the 6W4 socket. The RED end of the rectifier should connect to pin 3 and the BLACK end to pin 5. This part of the circuit operates at 1300V; therefore, be sure to locate the rectifier and its leads to provide ade quate insulation. Use spaghetti on the rectifier leads. Keep the rectifier leads short to avoid rectifier vibration problems. 3. This completes the modifications. Service bulletin 104 also relates to this product. If trouble has been experienced this modification should be installed at this time. MI-2/MI-3