McIntosh MR 80 Service Manual

Page 2

TABLE OF CONTENTS

Section 0: GENERAL INFORMATION

General Notes ....................................... 0-3
Top and Front Views. . . .0-4
Hear and Side Views. . . .0-5
Symbol Designations. . .0-5
Block Diagram. . .0-9
Exploded View - G 0-10
Exploded View - Top. . . 0-11
Exploded View - Botto 0-12

Section 1: INTERCONNECTION
Interconnection Diagram ............................. 1-3
Parts List - Interconnection. . . .1-4
Parts List - Front Panel and Trim
Parts List - Installation Hardware. .

Section 2: ANTENNA SWITCH ASSEMBLY
Schematic ..........................................
Section Notes ......
Semiconductor Ident cation
PC Board Layouts .........
Section Location ~ Top View.
Parts List. . .
Block Diagra

Section 3? RFI IF ASSEMBLY

Section Notes ....................................... 3-1
Block Diagram ..........

Section Location- Top VIew.
Semiconductor Identification
PC Board Layouts
Schematic. . .
Parts List .......................................... 3-10

Section 4: MULTIPLEX, FM MUTING a NOISE FILTEFI
Section Notes. . .
Block Diagram
Section Location -
Semiconductor Identification
PC Board Layouts .......
Schematic ...... .
Parts List .......................................

Section 5: HEADPHONE AMPLIFIER 81 TURN-ON DELAY
Section Notes. ............. 5-1
Block Diagram
Section Locatio .
Semiconductor Identification.
PC Board Layouts ..........

Schematic ...... . .5-7
Parts List ........................................... 5-9
Section 6. TOUCH CONTROL & DISPLAY FUNCTIONS
Section Notes. .6-1
Block Diagram .6-2
Section Location p 45.3
Semiconductor Identification. .6-4
PC Board Layouts ......... .6-6
Schematic ...... .69
Parts List .......................................... 6-10
Section 7: PRESET SCAN & TOUCH CLOCK
Section Notes... . .1-1
Block Diagram. .7-2
Section Location op Iew. .7-3
Semiconductor Identification . .7-4
PC Board Layouts ......... .7-6
Schematic ...... _7.g
Parts List ........................................... 1-9

Section 8: CONTROL LOGIC, TUNING VOLTAGE & TUNING LOCK

Section Notes ......... -1
Block Diagram. . 2
Section Location - Bottom VIew. . ,3
Semiconductor Identification. .8-4
PC Board Layouts ......... .8-6
Schematic ...... . 8-9
Parts List .......................................... 8-10

0-2

Section 9: TOP COVER CONTROLS, BAND LIMITS,
MAIN 8: PRESET TUNING
Section Notes ....................................... 9-1
Block Diagram ...........
Section Location - Top View
Semiconductor Identification.
PC Board Layouts. .
Schematic
Parts List. . . .

Section 10: FREQUENCY COUNTER ASSEMBLY
Section Notes ...................................... 1
Block Diagram ..............
Section Location - Bottom View
Semiconductor Identification. .
PO Board Layouts.
Schematic ....... .
Parts List ......................................... 10-

OOOUIMN-l-

Section 11: POWER SUPPLY
Section Notes ......................................
Block Diagram.
Section Location - Botto
Semiconductor Identification .

' 4L...
inbred

4......

PC Board Layouts #2 ...... .11-5
PC Board Layouts #1. .11-6
Schematic ........ 11.3

Parts List ............. I ........................... 211-9

\

Section 12: ALIGNMENT PROCEDURE
Performance Specifications
Test Equipment Required
Test Equipment Connectio ..
PC Board Alignment Location
Preaiignment Procedure .....
Alignment Procedure... . .
Section Location Views ............................. 12-12

Section 13: L? LOGIC DIAGRAMS 81 CIRCUIT

PERATION
IC Logic Diagrams .................................. 13-1
Logic Truth Tables. . .13-3
Circuit Operation ................................... 13-4

Section 14: SHIPPING CARTON
Flepacking Instructions ......
Shipping Carton Assembly Vi

Page 3

1.

2.

M R80

GENERAL NOTES

Unless otherwise noted, all voltages indicated
on the schematics are measured under the
following conditions:

a. AC input at 120 volts, 50 I 60Hz.

b. Except for the regulated circuits in the
power supply, all voltages are 120%
with respect to ground. A high im»
pedance voltmeter must be used.

c. No signal at antenna or cable input ter-
minals.

d. Front panel controls set at:

SELECTIVITY ...... NARROW
FILTER ................ OUT
MODE ............. STEREO
SCAN ......... CCW or SLOW
MUTING ............... OUT
VOLUME ..... . .......... ON
e. Top panel controls set at:
PRESELECTOR ......... OUT
lNPUT ................. ANT
LOCK .................. 0N

DE-EMPHASIS. . . .75uS & OUT
SIGNAL STRENGTH. . . .CCW

f. Rear panel controls set at:
STATIONS .......... PRESET

Unless otherwise specified:

a. Resistance values are in ohms, 1/4 watt,
5% tolerance.

b. Capacitance values smaller than 1 are
in microfarads (uF), and capacitance
values greater than 1 are in picofarads
(9F)-

c. Inductors are in microhenries (MH).

When the MR 80 is connected to the 120V line
voltage, but is not connected to any other
device (preamp, power amp, antenna, test
equipment, etc.), there is a chance the frequen-
cy display will blank out when tuning with the
main tuning knob. This is normal and can easily
be corrected by reversing the 120V AC line plug,
or by connecting the MR 80 to any other equip-
ment.

Logic voltage levels:

a. All logic is positive. The most positive
voltage level is a logic high or 1.

b. The symbol for B-series CMOS is a dou-
ble quotation mark:
0 or logic low (-.32V to +4V)
1" or logic high (+11.9V to +15.3V)

c. The symbol for TTL and low power
Schottky is a single quotation mark:
0 or logic low (-.7V to +.8V)
1 or logic high (+2V to +5V)

d. The symbol for ECL is a double dash
line:

-0- or logic low (-1.475V to -1.85V)

-1- or logic high (-1.105V to -O.81V)

Logic Truth Tables: Refer to page 13-3

Many of the semiconductor devices (CMOS and
NMOS) used in the MR 80 are inherently sen-
sitive to static electricity when not connected
to a circuit, and can be permanently damaged
by a static electricity discharge. When these
devices are removed from a circuit, they should
have their leads embedded in conductive-
carbon foam or aluminum foil to protect them.
Follow the removal and installation procedures
below to insure against static electricity
damage.

TO REMOVE:

a. Turn power off to the MR 80.

b. Touch one hand to the chassis, then
remove the semiconductor from the cir-
cuit with the other hand.

0. Touch one hand to the conductive-
carbon foam (or aluminum foil), then
embed the leads of the semiconductor
in the foam with the other hand.

TO lNSTALL:

a. Turn power off to the MR 80.

b. Touch one hand to the conductive foam
(or aluminum foil), then remove the
semiconductor from the foam with the
other hand.

c. Touch one hand to the chassis, then in-
stall the semiconductor in the circuit.

0-3

Page 6

SYMBOL DESIGNATIONS

The heavy lines on the schematics denote the 4. A D" between the collector and emitter of a
primary signal path. transistor symbol on the circuit side of a PCB
layout identifies the transistor as a Darlington
The terminal numbering of rotary switches is transistor.
for reference only. A dot on the rotor of a rotary
switch indicates there is an electrical connec- 5. Marking to identify location of controls:
tion between the front and rear rotor section.
Front panel
Letter designations for symbol numbers:
C - Capacitors (MUTING) Rear panel
CB . Circuit Breaker
D - Diodes MUTING Top panel
DS - Lamps and Lighting Devices .
E - Ferrite Beads 6. All schematic symbols used in this manual are
F - Fuses in conformance with the book, Electrical and
FM - Filters Electronics Graphic Symbols and Reference
IC - Integrated Circuits Designations" published by the Institute of
J - Jack Electrical and Electronics Engineers. (lEEE Std
K - Relay 315-1975, ANSI Y32.2-1975, and CSA 299-1975)
L - Inductors, Coils and Chokes
LDR - Light Dependent Resistors
M - Meters
Q - Transistors
R - Resistors and Potentiometers
RT - Thermistors
S - Switches
T - Transformers
Y - Crystals
PCB OUTL'NE [551538 OUTLINE
I TES -
Eqélfigakism l/SVEIgEngEgEEgM
TO INCLUDE -" OR GOES TO SECTION 8
SECTION II /2>-Ia
\WIRE CONNECTS

PLUG DISCONNECT-j
PLUG 0N PCB

PLUG DISCONNECT-
RECEPTACLE 0N Poms

SOLDER CONNECTION
T0 PCB

@-

0-6

WITH PIN IS ON

Izl\$ECTl0N e
1:] No CONNECTION-

REFERENCE NUMBER

KFOR LOCATION ONLY
PCB GROUND

\\EARTH GROUND
CHASSIS GROUND