McIntosh MC 250 Operating and installation instructions

MC 250
SERVICEINFORMATION
STARTING WITH SERIAL NO. 23L48
MCINTOSHLABORATORYINC.2 CHAMBERSSTREETBINGHAMTON,NEWYORK

MC250
ELECTRICALSPECIFICATIONS
PowerOutput:
100wattsRMScontinuous,50wattsperchanneloperating
simultaneously,into4 ohm,8 ohm,or16ohmloads.
HarmonicDistortion:
Lessthan0.25%atratedpoweroutputfrom20Hzto20,000Hz.
IntermodulationDistortion:
Lessthan0.25%foranycombinationoffrequenciesbetween
20Hzand20,000Hz.
FrequencyRange:
Atratedoutputbothchannels:+0to-0.25dBfrom20Hz
through20,000Hz.
OutputDampingFactor:
Greaterthan10foranyoutputtap.
InputSensitivity& Impedance:
Inputsensitivityis0.5volts.InputimpedanceIs200Kohms.
Hum& Noise:
Greaterthan90dBbelowratedoutput.
PowerRequirements:
117voltsAC,50-60Hz,50wattsatzerosignaloutput,250
wattsatratedoutput.

MC250

MC250
LEFT CHANNEL POWER OUTPUTPRINTEDCIRCUITBOARD 043-916
RIGHTCHANNEL POWER OUTPUTPRINTEDCIRCUITBOARD 043-916
INPUT SECTION PRINTED CIRCUIT BOARD 043-795

MC250

MC250

SCHEMATICNOTES
MC250
1.Unlessotherwisespecified:Resistancevaluesareinohms,1/2watt,and
10%tolerance;capacitancevaluessmallerthan1 areinmicrofarads(µF);
capacitancevaluesgreaterthan1 areinpicofarads(pF);inductorsarein
mic rohenr i es(µH).
2.Printedcircuitboardcomponentsareoutlinedontheschematicsbydotted
lines.Thecirclednumbersonthedottedlinescorrespondtothenumbers
onthePCBoardlayouts.
3.Theheavylinesontheschematicsdenotetheprimarysignalpath.
4.Allvoltagesindicatedontheschematicsaremeasuredunderthefollowing
conditions:
a.Useofan11megohmimpedanceVTVM.
b.Allvoltages±10%withrespecttochassisground.
c.Nosignalatinputterminals.
d.ACinputat117volts,50/60Hz.
e.Frontpanelcontrolsat:
LeftGain
RightGain
Mode
FullyCCW
Fully CCW
Stereo
5.InunitswithSerialNo.'sbelow28L21:R88,R89,R90& R91areused;
R49& R50are2200W;R86& R87are160W;andR33& R34are33k.
6.InunitswithSerialNo.'sfrom28L60to37L75,C5& C6are180pF.
Q21 Q25
BOTTOMTOP
Q19 Q23
BOTTOMTOP
Q20
BOTTOM
LOCATIONOFTRANSISTORSNOTONPRINTEDCIRCUITBOARDS
Q26
TOP
Q22
BOTTOM
Q24
TOP

MC250
REPLACEMENTPARTS
Allpartsnotlistedarecommonitems
ablefromradiopartsjobbers.
Rep1acementpartsmaybeobtainedwhen
byPARTNUMBERfrom:
MclntoshLaboratoryInc.
CustomerServiceDepartment
2ChambersStreet
Binghamton,NewYork13903
(telephone[phone])
Symbol
Number
Cl1, 12
C27,28
C29
C47,48
C51,52
C53,54
C55,56
C57
D1,2
D5,6
07,8
D13,14
D15,16
D18
D20
D25,26
D27,28
D31,32
Fl
Q1,2
Q3,4
Q5,6
Q7,8
Q9.10
Q11,12
Q15,16
Q17,18
Q19,20
Q21,22
Elect.
Elect.
Elect.
Mylar
Elect.
Elect.
Elect.
Elect.
si.
Si.
Si.
Si.
Si.
Si.
Si .
Si.
2.5A
Si.
Si .
si.
Si.
Si.
Si.
Si.
Si.
Si.
Si.
CAPACITORS
Description
470µF4V
9300µF45V
80/80/150/50µF
200/200/150/150V
.47µF
100µF 15V
10µF 25V
640µF25V
500µF50V
DIODES
referencediode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
rectifierdiode
FUSES
circuitbreaker
TRANSISTORS
NPNtransistor
NPNtransistor
PNPtransistor
PNPtransistor
PNPtransistor
NPNtransistor
NPNtransistor
PNPtransistor
NPNtransistor
PNPtransistor
obtain-
ordered
Part
Number
066-136
066-106
066-095
064-045
066-127
066-005
066-157
066-137
070-046
070-022
070-022
070-O4
070-041
070-031
070-031
070-031
070-031
070-022
088-001
132-054
132-054
132-056
132-056
132-056
132-515
132-021
132-032
132-524
132-530
Q23,24
Q25,26
Rl
R2
R43,44
R57,58
R59,60
S1,2
S3
Tl
T2
T3
Si.NPNtransistor132-070
Si.NPNtransistor132-070
POTENTIOMETERS
Leftgain134-206
Right/monogain134-206
RESISTORS
Wirewound3.6k5W139-065
Wirewound.56W5W139-048
Wirewound.33W5W139-071
SWITCHES
Thermalcutout153-007
Modeselector153-008
TRANSFORMERS
Powertransformer043-605
Output transformer (right) 043-667
Outputtransformer(left)043-668
MISCELLANEOUSITEMS
Plasticfeet017-040
Ownersmanual038-287
Gaincontrolknob090-017
Shipping carton 033-077
ACpowercord170-021
15C01047S-M1508
SCHEMATIC PART NO. 038-508