McIntosh MR67 Tuner Service Information.pdf

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1、TUNER CONTENTS INTRODUCTION. . 1 FM ALIGNMENT. . 2 MULTIPLEX ALIGNMENT. . 4 PARTS LIST. 6 SPECIFICATIONS.11 CHASSIS LAYOUT. 12 SCHEMATIC DIAL STRINGING 2 CHAMBERS ST. BINGHAMTON, N.Y. I 30 0) si Iftlntosh INTRODUCTION All McIntosh tuners are carefully aligned and tested at the factory using the fine

2、st available test equipment. All McIntosh tuners will meet their pub lished specifications when shipped from the factory. After extensive operation, especially when tubes have been replaced, it may be desirable to realign the tuner circuits for best performance. This manual gives complete informatio

3、n on the circuit realignment procedure for the MR 67 tuner. The test equipment listed below (or its equivalent) is necessary to properly align an MR 67. The accuracy of the alignment will be directly related to the accuracy and calibration of the test equipment used. FM Signal Generator (Measurement

4、s 210A or equivalent) 10.7 MC Generator (Preferably crystal controlled) VTVM Multiplex Generator (RCA WR-51A or equivalent) Oscilloscope (Hewlett-Packard 120B or equivalent) Harmonic Distortion Analyzer, desirable but not essential(Hewlett- Packard 330B or equivalent) If the necessary test equipment

5、 is not available, alignment should not be attempted. You may contact the McIntosh Customer Service Department for additional information. Customer Service McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York Our telephone number is 723-5491 The direct dial area code is 607 1 MR 67 FM ST

6、EPS TUNER DIAL SETTING SIGNAL GENERATOR INDICATOR FREQ COUPLING MODULATION TYPE CONNECTED TO 1 Point of no interference or signal 10.7MC Through external .01 MF cap to pin 7 of 12AT7 mixer cw VTVM tp #1 2 SAME SAME SAME SAME MX 110 tuning eye 3 SAME SAME SAME SAME VTVM TP #2 4 SAME SAME SAME SAME SA

7、ME Pin 6 of discriminator transformer 5 105MC 105MC 300 ohm antenna terminals with matching network 400 cycles 75KC deviation (100% modulation) VTVM connected to TP1 and scope connected to L or R audio output 6 90MC 90MC SAME SAME SAME 7 105MC 105MC SAME SAME SAME 8 90MC 90MC SAME SAME SAME 9 Point

8、of no interference Scope L or R output 10 105MC 105MC SAME 400 cycles 75KC deviation (100% modulation) attenuated to 2.5 microvolts output VTVM connected to TP #1 and Scope connected to L or R audio output ANTENNA MATCHING NETWORK 100 OHMS * JA/r-O TUNER 300 OHM ANTENNA sAA-0 TERMINALS 150 OHMS * IF

9、 SIGNAL GENERATOR HAS OTHER THAN 50 OHM INTERNAL IMPEDANCE, USE A RESISTOR OF 150 OHMS, LESS INTERNAL GENERATOR IMPEDANCE. FM SIGNAL GENERATOR ALIGNMENT ADJUST TEST LIMITS REMARKS Top (secondary) and bottom, (primary) of 1st, 2nd and 3rd IF transformers Maximum possible negative voltage Shunt to gro

10、und the winding not being adjusted with a .01 MF capacitor in series with a 1 K resistor. Attenuate signal generator until output voltage at TP #1 is less than 1.5 volts with one IF transformer winding shunted. IF transformers have terminal #1 marked with a green dot and are numbered clockwise. 4th

11、IF transformer, top and bottom. Eye should close to approx. /16 with strong signal. Make additional adjustments of eye closure by varying the spacing of parallel conductors connected to pins 1 and 4 of the 4th IF transformer. (This changes the capacitive coupling between pins 1 and 4.) Discriminator

12、 transformer top core (secondary) Adjust for 0 volts Discriminator transformer bottom core (primary) Maximum negative voltage Repeat step 3 if a large change is made in the setting of the bottom core. Oscillator trimmer cap. Maximum negative voltage As output increases, attenuate signal generator to

13、 keep maximum output at TP #1 to less than 2 volts. Oscillator coil tuning slug SAME Repeat steps 5 and 6 until dial calibration is accurate. Mixer trimmer and RF trimmer SAME Mixer coil tuning slug and RFcoil tuning slug SAME Repeat steps 7 and 8 until output is as high as possible. Muting adj. con

14、trol Turn muting switch to in position. Adjust muting control until background noise just disappears. IHFM sensitivity 2.5 microvolt for less than 3% total noise and distortion Step 10 is an overall sensitivity check, and requires a distortion analyzer and FM signal generator with attenuator. With 2

15、.5 microvolts input at the 300 ohm antenna terminals, TP #1 voltage should be .6 volts or more. 3 MR 67 MULTIPLEX TUNER DIAL SETTING Point of no interference or signal SAME 100MC SAME SAME SAME SAME SAME SIGNAL GENERATOR INDICATOR FREQ. COUPLING MODULATION TYPE CONNECTED TO Audio generator set to 67

16、 KC, 0.5 volts output or less TP #2 Audio VTVM Pin 6 of 38KC transformer (yellow wire connected at this pin) MPX generator with 19KC pilot attenuated to approx. 5% level (5 % level is A of normal 10% level) 19KC pilot must be attenuated for correct alignment SAME SAME Pin 3 or 8 of 12AU7 MPX oscilla

17、tor 100MC modulated by MPX generator, 19KC pilot at normal output 300 ohm antenna terminals with approx. 1000 microvolt signal 1 KC 100% modulation (34KC deviation) modulating left or right only SAME Pin 1 or 2 of 38KC transformer SAME SAME SAME Audio VTVM and scope Lor R output jack SAME SAME SAME

18、SAME SAME SAME SAME SAME SAME SAME SAME SAME Turn off 1 KC audio modulation SAME SAME SAME SAME Same as step 3 SAME SAME i DECODER ALIGNMENT ADJUST TEST LIMITS REMARKS 67KC trap Adjust for minimum voltage 19KC phase coil and 19KC transformer 1. Disable local 38KC oscillator by placing a jumper wire

19、across 6.8K resistor connected to pins 1 and 6 of 12AU7 MPX oscillator. 2. Shunt pin 2 of 19KC transformer to ground with .01 capacitor in series with 1 K resistor. 3. Adjust 19KC phase coil for maximum output. Proper adjustment places core approx. A from bottom of coil form. 4. Adjust bottom core o

20、f 19KC transformer for maximum output. 5. Shunt pin 3 of 19KC transformer to ground with .01 capacitor in series with 1 K resistor. 6. Adjust Top core of 19KC transformer for maximum output. 7. Remove jumper used in step 1 above. 38KC transformer bottom core Adjust for maximum voltage 38KC transform

21、er top core Adjust for stable scope display 1. Turn off 19KC pilot on MPX generator. 2. Adjust top core of 38KC transformer to obtain a stable and uniform 1 KC signal scope display. This adjustment may be critical, so turn core very slowly. 3. Turn 19KC pilot back on. 19KC phase coil 30db separation

22、 or more Modulate left channel and measure right channel output. Adjust 19KC phase coil for minimum right channel output (maximum separation). Remove all test leads from TP #2 for separation checks. SAME Modulate right channel and measure left channel output. Separation in steps 5 and 6 should be at

23、 least 30db This step checks the rejection of 19KC and 38KC frequencies. Residual output should be at 1 least 40db below modulated output. 1 Check for MPX indicator light 1. MPX light should turn on with MPX signal 2. Tuning slowly across dial, MPX light should turnon only with MPX signal. 5 MR 67 P

24、ARTS LIST TUBES ITEM NO. USE IDENTIFICATION NUMBER VI RF Amplifier 1 6DS4 V2 RF Amplifier 2; Mixer 12AT7 V3 Oscillator 6AB4 V4 IF Amplifier 1 6AU6 V5 IF Amplifier 2 6AU6 V6 IF Amplifier 3; Limiter 1 6AU6 V7 IF Amplifier 4; Limiter 2 6CS6 V8 Muting Amplifier; AGC Clamp 6AV6 V9 Tuning Indicator EMM801

25、 VI0 Left Audio Amplifier 6BL8 VII Right Audio Amplifier 6BL8 VI2 MPX Amplifier at least 60 db quieting between stations. Drift Less than 25KC. Image Rejection Better than 60 db. Hum Better than 70 db below 100% modulation. Output Approximately 2.5 volts, low-source impedance. Antenna Inputs 300 ohm

26、s balanced, 75 ohms unbalanced. RF Amplifier Cascode with 6DS4 Nuvistor in first stage. IF Amplifiers Four stages; AGC used to insure that limiting occurs only in the limiter stages. Tuning Indicators Dual electron ray tube; lower section for precise tuning indication; upper section for signal stren

27、gth presentation (can be switched to indicate multi- path distortion). FM Multipath Distortion Indicator An exclusive new McIntosh development; the upper section of the dual electron-ray tube can be switched to indicate multipath distortion or signal strength. Multiplex Channel Separation Better tha

28、n 30 db at 1000 cycles. Multiplex Filter Greater than 40 db suppression below 100% modula tion of 19KC pilot and 38KC carrier. Multiplex Indicator MPX stereo light activated by 19KC carrier. Multiplex Type Peak-detecting, self-matrixing circuit. IF Bandwidth 200KC flat top response, down 3 db at 200

29、KC. Limiters Two stages. Radiation Substantially below FCC requirements. Tube and Semiconductor Complement 1 6DS4 Nuvistor 1st RF amplifier. 1 12AT7 2nd RF amplifier and mixer. 1 6AB4 Oscillator. 1-6AU6 1st IF. 1-6AU6 2nd IF. 16AU6 3rd IF; 1st limiter. 1 6CS6 4th IF; 2nd limiter. 16AV6 Muting amplif

30、ier; AGC clamp. 1EMM801 Tuning indicator, signal strength in dicator, Multipath distortion indicator. 1 6U8 MPX amplifier and 19KC separator-indi cator control. 1 -12AU7 MPX 38KC oscillator. 2 6BL8 left and right audio amplifiers. 1 MA113 Transistor (multiplex indicator lamp switch). 2 1N542 Diodes,

31、 wide band discriminator. 41 N542 Diodes, balanced MPX detector. 21N542 Diodes, balanced detector for MPX indicator. 1 1N541 Diode, muting and tuning indicator detector. 2 Selenium rectifiers, high-voltage supply. 11850 pilot lamp, MPX indicator. Power Consumption 50 watts, 105 to 125 volts, 50 to 6

32、0 cycles. Dimensions Front panel; 16 inches wide by 57/i6 inches high; chassis (including PANLOC shelf) 15 inches wide by 5% inches high by 13 inches deep, in cluding connectors; clearance in front of mounting panel including knobs, 1 % inches. Weight Tuner only, 24 % pounds. In shipping carton, 33

33、pounds. Finish Anodized gold and black front panel; chrome chassis. Installation Convenient professional PANLOC, (see PANLOC Installation folder.) 11 LABORATORY INC. 2 Chambers St., Binghamton, N. Y Made in U.SA PhoneArea Code 607-723-6481 Design subject to change without notice. MODEL NUMBER: MR 65

34、B, MX 110, MR 67 DATE: MARCH 1965 MODIFICATION: To allow adjust control for instant correction of tube and circuit variations. This will insure proper MPX indicator light operation. PROCEDURE: This modification will allow you to adjust the MPX light on all tuners with ease. The reason for this modif

35、ication is to allow simple field adjustment of varying tube and circuit characteristic. MR 65B and MX 110 tuner/preamp. 1. Install IK control (WC 807) to MPX chassis. Use the existing MPX chassis mount ing screw. 2. Remove the 820 ohm or IK ohm resistor, (cathode circuit of 6U8) 3. Solder one end of

36、 470 ohm resistor to bottom hole nearest the chassis. 4. Connect a lead from other end of the resistor to the terminal lug on a 1K control. 1. Install IK control to the tuner chassis under the existing screw as shown in the diagram. 2. Follow steps 2, 3, 4, as above. TO ADJUST THE CONTROL: Tune to point of no station. Place mute to IN position. Turn control from full clockwise position to a point where the light just goes out. MR 65B, MX 110, MR 67