McIntosh MR55 Tuner Service Information.pdf

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1、INSTRUCTION MANUAL mcintosh model mr-55 AM-FM TUNER (Serial No. 1KOOO and up) mcintosh laboratory, inc. 2 Chambers St. Binghamton, N. Y. U.S.A. INSTALLATION INSTRUCTIONS FOR THE McIntosh mr-55 am-fm tuner The MR-55 may be mounted in its own cabinet or shelf mounted in a custom cabinet. The tuner has

2、 been designed to mount on a shelf rather than hang from the cast tuner panel. Rubber shock mounting feet have been provided to offer the optimum in mechanical isolation from extraneous vibrations. Enclosed in the instruction manual envelope are two copies of the “TUNER PANEL CUTOUT TEM PLATE” and t

3、wo copies of the “SHELF MOUNTING TEMPLATE” for mounting the MR-55. Prepare the cabinet for the mounting of the MR-55 by first cutting the wooden cabinet panel to receive the cast tuner panel. 1. On the back of the wooden cabinet panel make a vertical center line on the exact center of the area in wh

4、ich the tuner will mount. Extend this center line to the shelf. 2. Fold the “TUNER PANEL CUTOUT TEMPLATE” on the “FOLD LINE.” The “FOLD LINE” is the line of the top of the shelf on which the tuner will mount. 3. Place the “TUNER PANEL CUTOUT TEMPLATE” in the proper location on the inside of the cabi

5、 net with the fold line against the shelf. The template center line should match the center line scribed on the panel in step 1. 4. In the center of the “Cutout Area” on the “Tuner Cutout Template” are two holes marked “LOCA TION HOLES.” Carefully and accurately drill these two holes with a 5/32 inc

6、h drill. 5. Transfer the “TUNER PANEL CUTOUT TEMPLATE” to the. front of the wooden cabinet panel. Match the “LOCATION HOLES” for the proper positioning of the template. Proceed with marking the lo cation of the six holes and the outline of the cutout on the front of the wooden cabinet panel. IMPORTA

7、NT: DRILL THE FOUR 3/16 INCH AND THE TWO 5/32 INCH HOLES BEFORE CUTTING OUT THE TUNER PANEL HOLE. The cast tuner panel has a 1/4 inch overlap to cover the edges of the cutout in cabinet panel. Next prepare the shelf for mounting the tuner. 1. Measure the thickness of the wooden cabinet panel. 2. “FO

8、LD LINES” have been supplied on the “SHELF CUTOUT TEMPLATE” for standard panel thickness up to one inch. Fold on correct fold line for your wooden panel thickness. 4. Place the folded edge of the template against the back of the front panel. The template center line must match the center line extend

9、ed to the shelf in step #1 of the front panel cutout instructions. 5. Carefully mark the locations of the four 1/4 inch holes and the 8 by 10 1/4 inches, ventillation hole. 6. Drill and cut out the shelf. Next prepare the MR-55 for mounting in the cabinet by removing the pressed wood shipping pallet

10、 from the bottom of the tuner. Remove the knobs by gently pulling them toward you. Remove the felt washers. The cast tuner panel has been attached to the tuner by two angle brackets that are for shipping pur poses only. These are removed by unscrewing the four screws (two on each side! that hold the

11、 angle brackets to the tuner chassis. After removing these four screws the tuner panel can be slipped off over the knob shafts. After removing the tuner panel lay it face down on a protected surface for the following operations. Remove the four 6/32 screws (one on each corner) that hold the two ship

12、ping brackets to the tuner panel. 3 The McIntosh MR-55 is a superior quality AM-FM Tuner for use in home music systems and profes sional applications where distortion free reception is needed. Typical professional uses are “off the air” re cording, broadcast monitor, rebroadcasting, etc. A thorough

13、perusal of this instruction manual will give greater enjoyment and better listening. The MR-55 is the finest tuner available and complete familiarity with its functions and operation will result in the out standing performance you expect from a McIntosh product. SPECIFICATIONS: AM FM Sensitivity: 1.

14、5 microvolts Selectivity: Narrow Position: 4 K.C. Bandwidth, 10 K.C. from center down 53 D.B. Medium Position: 13 K.C. Bandwidth, 10 K.C. from center down 20 D.B. Broad Position: 20 K.C. Bandwidth (Measurements include R.F. and I.F. circuits. Charac teristics substantially unchanged over entire R.F.

15、 tun ing range.) A.V.C.: Exceptionally strong; less than 4 D.B. audio output change with input changes from 10 microvolts to 100,000 microvolts. Distortion: Less than 1% at 100% modulation Hum: 50 D.B. below full signal Bandwidth: I.F. at 600 K.C.20 K.C.; at 1600 K.C.20 K.C. R.F. at 600 K.C.21 K.C.;

16、 at 1600 K.C.23 K.C. Audio Bandwidth: Broad Position 3 D.B.20 to 10 K.C. Medium Position 3 D.B.20 to 6.5 K.C. Narrow Position 3 D.B.20 to 2.0 K.C. Sensitivity Selector: Three Positions Front End: 21 K.C. Constant bandwidth, band pass input Whistle Filter: 70 D.B. rejection 10 K.C. Sensitivity: 3 Mic

17、rovolts at 100% modulation ( 75 K.C. Dev.) for less than 3% total noise and distortion (Based on I.H.F.M. (proposed) standards for measuring F.M. Tuners) Capture Ratio: 1 to 0.8 I.F. Amplifiers: Four I.F. Bandwidth: 200 K.C.; Flat on Top I.F. Transformers: Mechanically captive Limiters: Two; zero ti

18、me constant grated-beam followed by a 0.5 microsecond pentode limiter Limiter and Detector Bandwidth: 2 Megacycles Frequency Response: 3 D.B.; 20-20,000 cycles Hum: 75 D.B. below full signal A.F.C.: Separate detector; strong, distortion free, com pletely variable Drift: 30 K.C. without A.F.C.; negli

19、gible with A.F.C. Antenna Input Impedance: 300 ohm balanced; 72 ohm unbalanced Radiation: Substantially below F.C.C. requirements TUBE COMPLEMENT: VI6BZ7 F.M. R.F. Amplifier V26BZ7 F.M. Reactor and F.M. Os V36AB4 F.M. Mixer V46BJ6 1st I.F. Amplifier V56AU6 2nd I.F. Amplifier V66BJ6 3rd I.F. Amplifie

20、r V86AU6 4th I.F. Amplifier V76AL5 A.M. Detector and A.V.C. Detector V96AL5 P.M. A.V.C. V106BN6 1st Limiter VI16AU6 2nd Limiter VI26AL5 F.M. Detector V136BV8 AFC Detector V146BA6 A.M. R.F. Amplifier VI56BE6 A.M. Converter V166AL5 A.V.C. Clamper V1712AU7 Squelch Amplifier and F.M. Metering V1812AU7 A

21、udio Amplifier and Cathode Follower SIZE: 4% Inches High x 14% Inches Wide x 12 Inches Deep WEIGHT: Tuner Only: 17 Pounds, 3 Ounces; In Shipping Carton: 28 Pounds 2 INSTALLATION INSTRUCTIONS FOR THE McIntosh mr-55 am-fm tuner The MR-55 may be mounted in its own cabinet or shelf mounted in a custom c

22、abinet. The tuner has been designed to mount on a shelf rather than hang from the cast tuner panel. Rubber shock mounting feet have been provided to offer the optimum in mechanical isolation from extraneous vibrations. Enclosed in the instruction manual envelope are two copies of the “TUNER PANEL CU

23、TOUT TEM PLATE” and two copies of the “SHELF MOUNTING TEMPLATE” for mounting the MR-55. Prepare the cabinet for the mounting of the MR-55 by first cutting the wooden cabinet panel to receive the cast tuner panel. 1. On the back of the wooden cabinet panel make a vertical center line on the exact cen

24、ter of the area in which the tuner will mount. Extend this center line to the shelf. 2. Fold the “TUNER PANEL CUTOUT TEMPLATE” on the “FOLD LINE.” The “FOLD LINE” is the line of the top of the shelf on which the tuner will mount. 3. Place the “TUNER PANEL CUTOUT TEMPLATE” in the proper location on t

25、he inside of the cabi net with the fold line against the shelf. The template center line should match the center line scribed on the panel in step 1. 4. In the center of the “Cutout Area” on the “Tuner Cutout Template” are two holes marked “LOCA TION HOLES.” Carefully and accurately drill these two

26、holes with a 5/32 inch drill. 5. Transfer the “TUNER PANEL CUTOUT TEMPLATE” to the front of the wooden cabinet panel. Match the “LOCATION HOLES” for the proper positioning of the template. Proceed with marking the lo cation of the six holes and the outline of the cutout on the front of the wooden ca

27、binet panel. IMPORTANT: DRILL THE FOUR 3/16 INCH AND THE TWO 5/32 INCH HOLES BEFORE CUTTING OUT THE TUNER PANEL HOLE. The cast tuner panel has a 1/4 inch overlap to cover the edges of the cutout in cabinet panel. Next prepare the shelf for mounting the tuner. 1. Measure the thickness of the wooden c

28、abinet panel. 2. “FOLD LINES” have been supplied on the “SHELF CUTOUT TEMPLATE” for standard panel thickness up to one inch. Fold on correct fold line for your wooden panel thickness. 4. Place the folded edge of the template against the back of the front panel. The template center line must match th

29、e center line extended to the shelf in step # 1 of the front panel cutout instructions. 5. Carefully mark the locations of the four 1/4 inch holes and the 8 by 10 1/4 inches ventillation hole. 6. Drill and cut out the shelf. Next prepare the MR-55 for mounting in the cabinet by removing the pressed

30、wood shipping pallet from the bottom of the tuner. Remove the knobs by gently pulling them toward you. Remove the felt washers. The cast tuner panel has been attached to the tuner by two angle brackets that are for shipping pur poses only. These are removed by unscrewing the four screws (two on each

31、 side) that hold the angle brackets to the tuner chassis. After removing these four screws the tuner panel can be slipped off over the knob shafts. After removing the tuner panel lay it face down on a protected surface for the following operations. Remove the four 6/32 screws (one on each corner) th

32、at hold the two shipping brackets to the tuner panel -3- In the parts bag are six 6/32 x 1 1/4 inches threaded rods. Install these in the six drilled and tapped holes in the back of the tuner panel. 0 The tuner panel is now ready to be attached to the cabinet. The six threaded rods are inserted thro

33、ugh the two 5/32 inch and the four 3/16 inch holes in the cabinet panel. Secure the tuner panel to the cabinet panel by installing on the rods the 6/32 “KEP” nuts supplied in the parts bag. Bring the nuts up tight with a wrench or nut driver. The tuner can now be installed in the cabinet. The tuner

34、is secured to the cabinet shelf by the insertion of the four 10/32x3/4 inch thumb screws supplied in the parts hag through the 1/4 inch holes in the shelf. IMPORTANT: MAKE SURE THAT THE INNER CHASSIS FLOATS ON THE RUBBER SHOCK MOUNTING FEET, AND DOES NOT CONTACT THE CABINET OR TUNER PANEL. Next repl

35、ace the felt washers and knobs. Adequate ventilation is essential to the stable operation of any tuner. Do not put a solid back on the cabinet behind the tuner. If the tuner is mounted vertically make sure sufficient ventilation is supplied. Installation in the L-55 cabinet is done by the same proce

36、dure as for installation in a custom cabinet. The cabinets are supplied with the cutouts and holes all prepared. CONNECTING PROCEDURE FM ANTENNA: In high signal strength areas a minimum antenna, such as the folded dipole supplied, is all that is needed for local reception. Some care should be used i

37、n locating the folded dipole in a position that is free as possible from local noise sources and shielding such as metal roofing and building framework. The dipole should be mounted horizontally, and at 90 to the line of sight path to the transmitting stations. In fringe areas a good antenna is requ

38、ired. A highly directional broad band antenna used in conjunction with a rotor will result in superior performance in low signal strength areas. A substitute for the folded dipole can be an existing VIIF T. V. antenna. The MR-55 is supplied with an internal switching arrangement that eliminates the

39、need for two set couplers. The VHF T. V. antenna lead-in is connected to the antenna terminals marked “IM. ANT.” Connect the terminals marked “TO T. V. SET” to the antenna terminals on the T. V. receiver with 500 ohm antenna lead. When the MR-55 selector switch is in either of the “FM positions the

40、antenna is disconnected automatically from the T. V. receiver. In any other position of the selector switch the antenna is connected to the T. V. set and disconnected from the tuner. 6 75 OHM ANTENNA: The MR-55 has provision for the connection of a 75 ohm unbalanced antenna. The 75 ohm terminal scre

41、ws are next to the chassis on the back of the brown bakelite balun card located approximately 2 inches behind the tuning knob flywheel. The center conductor of the 75 ohm coaxial lead is attached to the screw terminal located 3/8 inch above the chassis. The outer conductor or ground side is connecte

42、d to the screw terminal located close to the chassis. Solderless spade lugs are supplied for your con venience. c 7 A. M. ANTENNA: Facilities are supplied on the MR-55 for the use of a low impedance loop antenna or a high impedance long wire antenna. AM reception will generally be improved through t

43、he use of a properly installed long wire outside antenna. For locations where an outside antenna is impossible or impractical a 10 foot loop antenna is supplied. The loop is attached between the terminals marked “HI” and “LO” on the “AM. ANT” terminal strip. The “AM. ANT” terminating switch, located

44、 left of center next to the phono input jack on the back panel of the tuner, must be in the loop position. Orientation of the loop is critical. It should be mounted in as large a circle as practical in the vertical plane. 8 An outside AM antenna is a wire as long as practical, mounted as high as pos

45、sible above the ground, at right angles to power lines. The lead in should be carefully positioned away from all A. C. lines. The “ANTENNA” terminating switch must be in “ANT” position when using outside or long wire antenna. A good ground can be of assistance in AM reception. A good ground is descr

46、ibed as a 1/2 inch rod 6 to 8 feet long driven into the earth. The ground wire is connected to the terminal marked “LO.” If the tuner is connected to an outside ground as described above do not connect any of the other equip ment to the same ground to prevent ground loops. Ground loops can cause an

47、increase in hum. For an alternate ground for use when using a long wire antenna connect the shorting link between termi nals marked “LO” and “GND.” 0 9 OUTPUT: Two pin jacks are supplied on the back panel marked “Output.” These jacks are in parallel. The output is unbalanced low impedance. Interconn

48、ect between either of these jacks and the tuner input of your preamplifier by means of the 6 foot shielded cable supplied with your tuner. Plug the A. C. cable from the tuner into one of the auxiliary A. C. outlets on the back of the preampli fier. 10 The A. C. cable from the amplifier can be plugge

49、d into the auxiliary A. C. outlet supplied on the back of the MR-55. This outlet is controlled by the A. C. switch on the front of the tuner. SEE ANTENNA INSTALLATION INSTRUCTIONS MCINTOSH POWER AMPLIFIER Multiplex Output The output on the back of the MR-55 marked “MULTIPLEX OUTPUT” is an unfiltered output for feeding a multiplex adapter. OPERATION The selector switch is a six position switch that has the following identifications: (1) F. M. LISTEN,