MC 250
SERVICE INFORMATION
S T A R T I N G W I T H S E R I A L N O . 2 3 L 4 8
MCINTOSH L A B O R A T O R Y INC. 2 CHAMBERS STREET BINGHAMTON, NEW YORK
MC 250
SERVICE INFORMATION
S T A R T I N G W I T H S E R I A L N O . 2 3 L 4 8
MCINTOSH L A B O R A T O R Y INC. 2 CHAMBERS STREET BINGHAMTON, NEW YORK
MC 250
E L E C T R I C A L S P E C I F I C A T I O N S
Power Output:
100 watts RMS continuous, 50 watts per channel operating
simultaneously, into 4 ohm, 8 ohm, or 16 ohm loads.
Harmonic Distortion:
Less than 0.25% at rated power output from 20Hz to 20,000Hz.
Intermodulation Distortion:
Less than 0.25% for any combination of frequencies between
20 Hz and 20,000 Hz.
Frequency Range:
At rated output both channels: +0 to -0.25dB from 20Hz
through 20,000Hz.
Output Damping Factor:
Greater than 10 for any output tap.
Input Sensitivity & Impedance:
Input sensitivity is 0.5 volts. Input impedance Is 200K ohms.
Hum & Noise :
Greater than 90dB below rated output.
Power Requirements:
117 volts AC,50-60Hz, 50 watts at zero signal output, 250
watts at rated output.
MC 250
MC 250
LEFT CHANNEL POWER OUTPUT PRINTED CIRCUIT BOARD 043-916
RIGHT CHANNEL POWER OUTPUT PRINTED CIRCUIT BOARD 043-916
INPUT SECTION PRINTED CIRCUIT BOARD 0 4 3 - 7 9 5
MC 250
MC 250
S C H E M A T I C N O T E S
M C 2 5 0
1 . U n l e s s o t h e r w i s e s p e c i f i e d : R e s i s t a n c e v a l u e s are i n ohms, 1 / 2 w a t t , and
10% t o l e r a n c e ; c a p a c i t a n c e v a l u e s s m a l l e r than 1 are i n m i c r o f a r a d s ( µ F ) ;
c a p a c i t a n c e v a l u e s g r e a t e r than 1 a r e i n p i c o f a r a d s ( p F ) ; i n d u c t o r s are i n
mi c rohen r i es ( µ H ) .
2 . P r i n t e d c i r c u i t board c o m p o n e n t s are o u t l i n e d o n t h e s c h e m a t i c s b y d o t t e d
l i n e s . The c i r c l e d numbers on the d o t t e d l i n e s c o r r e s p o n d to the numbers
on the PC Board l a y o u t s .
3 . The heavy l i n e s o n the s c h e m a t i c s d e n o t e the p r i m a r y s i g n a l p a t h .
4 . A l l v o l t a g e s i n d i c a t e d o n the s c h e m a t i c s a r e m e a s u r e d under the f o l l o w i n g
c o n d i t i o n s :
a. Use of an 11 megohm impedance V T V M .
b . A l l v o l t a g e s ± 1 0 % w i t h r e s p e c t t o c h a s s i s ground.
c. No s i g n a l at input t e r m i n a l s .
d . A C i n p u t a t 1 1 7 v o l t s , 50/60Hz.
e . Front p a n e l c o n t r o l s a t :
L e f t G a i n
R i g h t G a i n
Mode
F u l l y CCW
F u l l y C C W
S t e r e o
5 . I n u n i t s w i t h S e r i a l N o . ' s b e l o w 2 8 L 2 1 : R 8 8 , R89, R90 & R 9 1 are used;
R49 & R50 are 2200W; R86 & R87 are 160W; and R 3 3 & R34 are 3 3 k .
6 . I n u n i t s w i t h S e r i a l N o . ' s from 28L60 t o 3 7 L 7 5 , C 5 & C 6 a r e 180pF.
Q21 Q25
BOTTOM TOP
Q19 Q23
BOTTOM TOP
Q20
BOTTOM
L O C A T I O N O F T R A N S I S T O R S NOT O N P R I N T E D C I R C U I T B O A R D S
Q26
TOP
Q22
BOTTOM
Q24
TOP
MC 250
R E P L A C E M E N T P A R T S
All p a r t s not l i s t e d are common items
a b l e from r a d i o p a r t s jobbers .
Rep1acement p a r t s may be o b t a i n e d when
by PART N U M B E R from:
Mclntosh Laboratory Inc.
Customer S e r v i c e Department
2 Chambers Street
B i n g h a m t o n , New York 13903
(telephone 607 723-3512)
Symbol
Number
C l 1
, 1 2
C27,28
C29
C47,48
C51 ,52
C53,54
C55,56
C57
D1
,2
D5,6
07,8
D13,14
D 1 5 , 1 6
D18
D20
D25,26
D27,28
D31 ,32
Fl
Q1 ,2
Q3,
4
Q5,6
Q7,8
Q9.10
Q11 ,12
Q 1 5 , 1 6
Q17,18
Q19,20
Q21 ,22
E l e c t .
E l e c t .
E l e c t .
M y l a r
E l e c t .
E l e c t .
E l e c t .
E l e c t .
si.
Si
.
Si
.
Si
.
Si
.
Si
.
Si
.
Si
.
2.5A
S i .
Si
.
si.
Si
.
Si
.
S i .
Si
.
Si
.
Si.
Si
.
C A P A C I T O R S
D e s c r i p t i o n
470µF 4V
9300µF 45V
80/80/1 50/50µF
200/200/150/150V
.47µF
100µF 15V
10µF
25V
640µF 25V
500µF 50V
D I O D E S
reference diode
r e c t i f i e r d i o d e
r e c t i f i e r d i o d e
r e c t i f i e r diode
r e c t i f i e r d i o d e
r e c t i f i e r diode
r e c t i f i e r diode
r e c t i f i e r d i o d e
r e c t i f i e r d i o d e
r e c t i f i e r diode
FUSES
c i r c u i t breaker
T R A N S I S T O R S
NPN t r a n s i s t o r
NPN transistor
PNP t r a n s i s t o r
PNP t r a n s i s t o r
PNP t r a n s i s t o r
NPN t r a n s i s t o r
NPN t r a n s i s t o r
PNP t r a n s i s t o r
N P N t r a n s i s t o r
P N P t r a n s i s t o r
o b t a i n -
ordered
P a r t
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
1 3 2 - 5 1 5
1 3 2 - 0 2 1
132-032
132-524
132-530
Q23,24
Q25,26
R l
R2
R43,44
R57,58
R59,60
S1 ,2
S3
Tl
T2
T3
S i . NPN t r a n s i s t o r 132-070
S i . NPN t r a n s i s t o r 132-070
P O T E N T I O M E T E R S
Left g a i n 134-206
Right/mono g a i n 134-206
R E S I S T O R S
W i r e w o u n d 3.6k 5W 139-065
W i r e w o u n d .56W 5W 139-048
Wirewound .33W 5W 139-071
S W I T C H E S
Thermal cut out 153-007
M o d e s e l e c t o r 153-008
T R A N S F O R M E R S
Power t r a n s f o r m e r 043-605
Output transformer (right) 043-667
O u t p u t transformer (left) 043-668
M I S C E L L A N E O U S I T E M S
P l a s t i c feet 017-040
Owners m a n u a l 038-287
G a i n c o n t r o l knob 090-017
S h i p p i n g c a r t o n 033-077
AC power cord 170-021
15C01047S-M1508
S C H E M A T I C P A R T N O . 0 3 8 - 5 0 8