McIntosh MR 55A Owners Manual

Page 1

SPECIFICATIONS: AM Sensitivity: 1.5 microvolts Selectivity: Narrow (4 K.C. bandwidth) ± 10 K.C. from center down 53 D.B. Medium (13 K.C. bandwidth) ± 10 K.C. from center down 20 D.B. Broad (20 K.C. bandwidth) (Measurements include R.F. and I.F. circuits. The char- acteristics are substantially unchanged over entire R.F. tuning range.) Bandwidth: I.F. at 600 K.C. and at 1600 K.C; 20 K.C. R.F. at 600 K.C. 21 K.C.; at 1600 K.C.; 23 K.C. Audio Bandwidth: Broad Position ± 3 D.B.; 20 to 9.5 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 Whistle Filter: 70 D.B. rejection 10 K.C. Dimensions: 4¾" high x 14¾" wide x 12" deep FM Usable Sensitivity: 3 Microvolts at 100% modulation (± 75 K.C. Dev.) for less than 3% total noise and distortion I.H.F.M. standards. Capture Ratio: 1 to 0.8 I.F. Bandwidth 200 K.C.; Flat on Top I.F. Transformers: Mechanically captive Limiters: Two Limiter and Detector Bandwidth: 2 Megacycles Frequency Response: ± 3 D.B.; 20-20,000 cycles A.F.C.: Separate detector; strong, distortion free, com- pletely variable Drift: ± 30 K.C. without A.F.C; negligible with A.F.C Antenna Input Impedance: 300 ohm balanced; 75 ohm unbalanced V1-6BK7 F.M. R.F. Amplifier V2-6AB4 F.M. Mixer V3-6BA6 1st I.F. Amplifier V4-6AU6 2nd I.F. Amplifier V5-6AU6 3rd I.F. Amplifier V6-6AU6 1st Limiter V7-6AL5 A.M. Det. and A.V.C V8-6AU6 2nd Limiter V9-6BN8 A.F.C. Detector V10-6U8 F.M. Oscillator and Reactor V11-6BN8 Squelch Amplifier and Detector V12-6AB4 1st Audio V13-12AU7 Audio Output & F.M. Meter V14-6BA6 A.M. R.F. VI5-6BE6 A.M. Oscillator and Converter V16-6BW4 Rectifier Dl -IN542 Detector D2 1847 Pilot Lights (4) SIZE: 4¾ Inches High x 14¾ Inches Wide x 12 Inches Deep WEIGHT: Tuner Only: 17 Pounds, 3 Ounces; In Shipping Carton: 28 Pounds TUBE COMPLEMENT: -2-

Page 2

INSTALLATION INSTRUCTIONS FOR THE McINTOSH MR-55A AM-FM TUNER The McIntosh MR-55A 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 perusal of this instruction manual will give greater enjoyment and better listening. The MR-55A 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. The MR-55A may be mounted in its own cabinet or shelf mounted in a custom cabinet. 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 CUTOUT TEM- PLATE" and two copies of the "SHELF MOUNTING TEMPLATE" for mounting the MR-55A. Prepare the cabinet for the mounting of the MR-55A 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 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 the 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 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 cabinet 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 cabinet 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. 3. Place the folded edge of the template against the back of the front panel. The template center line must match the center line extended to the shelf in step #1 of the front panel cutout instructions.. 4. Carefully mark the locations of the four 1/4 inch holes and the 8 by 10 1/4 inches ventillation hole. 5. Drill and cut out the shelf. Next prepare the MR-55A for mounting in the cabinet by removing the pressed 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 side) that hold the angle brackets to the tuner chassis. (See Fig. 1.) 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 shipping brackets to the tuner panel. -3-