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 [phone])

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