Crown d75 User Manual

0-75

DUAL-CHANNEL

POWER

SERVICE MANUAL

CROWN INTERNATIONA

L,

INC. 17

AMPLIFIER

18

W. MISHAWAKA

RD.

ELKHART,

C 1989

Crown

IN

46517·4095

International. Inc.

K80186A6

3'

89

FULL THREE-YEAR WARRANTY

S

UMMARY

We,

CROWN

ORIGINAL PURCHASER AND

date

of

or exceed all

Weare
the serial number has been defaced, altered. or removed. It does nol cover damage \0 loudspeakers
Crown product failure. It does
e)(

clude$ batteries

We will remedy any defect in materials

or

ooless

make

be

equal to

depreciation

or

at the
time aftef receipt
including
between any foreign
shipments.)

YOli

must notify us

give you

it

for factory service. All components
Corrcctive
repairs

INTERNATIONAL.

purchase

by

advcn

the

original purchaser (warranty period) lhal1hc product is free of defects in materials or

iscd specifications for such a product.

INC

., 1718 West Mishawalca Road. Elkhart,

ANY

SUBSEQUENT OWNER

ITEMS

not responsible forproducl failure !;8uscd

nOI

cover defcclS

and

damage

caused

by leaky

or

workmanship by repair, replacement. or refund.

we

are unable to provide replacement, and repair

me

derective

Crown

sUrfaceshippingcoslS in the United States. will

or

malfunctioning component available 10

me

actual purchase price, not including interest, insurance, closing costs, and

on

the product from the

factory.

We

of

the defective product

country and the port

dateof

original purchase. Warranty work can only be performed at

will remedy the defect and ship the product from the sCJvice center

at

the aumoriz.cd service

of

entry in the United States and all

HOW

of

your

need

for warranty service not later than ninety (90) days after expiration

written ootice

action will be taken within a reasonable time

made

by

Crown

ofthcdcaler

or

the

authori7.cd

scrvice center.>

must

be

shipped in a factory pack, which,

serviceecnter

EXCLUDED

by

misu$(l,

ordamagccauscd

or

defective batteries.

WHAT

TO

OBTAIN

10

whom you

OF

WARRANTY

of

each NEW Crown product,

FROM

WARRANTY

accidcntornegieci.

by your use OfWl8Uthoril.oo modifications, parts,

WE

WILL

DO

is

not

be

practical

Crown

bome

or

cannot

free and clear

center

or

Crown

by

Crown. (Purchaser must bear thee)(pensc

WARRANTY SERVI

may

dclivcrthe

of

the date

of

roceiptofthe

arc not satisfactory, notify

Indiana46517-4095

This

warran\ydoc

We

may

be

timely

made. If

of

all liens or

other

factory. All e)(pcnses in remedying the

tues,

duties. and

CE

product.

or

we

will give you

if

needed,

may

beobtained

defective product by us

Crown

or

the authorized service

('Narrantor) warrant to you. the

for

a period

of

three (3)

workmanship

$ not extend [0 any produl:lon which
or

any other products resulting from

not

elect

refund unless you agr ee,

a rcfood

iselccted,

other

encumbrances.

finance charges less a reasonable

our

authorized servi

or

Crown

factory within a reasonable

other

custom's

of

the

warranty

an

from

or

our

yeaTS

from the

:md will mcet

or

service. It also

men

you must

The

refund will

ce

centers

defect.

of

shipping (he product

fee for suc h foreign

period. We

authorization 10 return

Crown

frec

of

charge.

scrvicecentcr.

center

If the

immediately.

will

YOU

ARE

NOT

EmTT'LED

FROM

ANY

DEFECT
RESULTING FR
INCroENTA
TO

YOU

NO PER
EXTENDED
REPLACEMENT
PORTION

We

reserve the right to

changes in

T HIS

WARRRANTY

STATE

TO

period.

CROWN

1

718

West Mishawaka Road,

TH

IS STATEMENT

OM

L

OR

,

SON

HAS T HE

BY

THE

OFTH

products previously manufactured.

STATE. No

INTERNAT

DI

SCLAIMER

TO

RECOVER

IN

OUR

PRODUCT.

SUC

H A

DEFECT.

CONSEQUENTIAL OAMAGES,SOT

OF

CONSEQUENTIAL

FROM

THIS

SOME STATES

WARRANTY

AUT

HOR

ITY

TO

ENLARGE, AMEND, OR

LENGT H
PARTS
IS

WARRANTY.

change

GIVES

action to enforce this Warranty shal1

IONA

OF

OF

TIME WHI

PROVlDEDUNDER THE

the design

of

any

CH YOU

prodUCI

LEGAL

YOU SPECJFIC

L,

INC.

LEGAL

Elkhart, Indiana

WARRANTY S

UPERSEDES

REMEDIES

46517·4095.

US ANY
INCLUDES

CONSEQUENTIAL

00

HE

ARE

TERMS

OFT

DESIGN

from time

RIGHTS,

be

commenced

ALL

AND INCIDENTAL

ANY

DAMAGE

NOT

ALLOW

ABOVE LIMI

ALTERATIONS

MODIFY

DEPRIVED

HIS

WAR

OF

RANTY SH

CHANGES

to

time without notice

OF

PURCHASER

AND

YOU

MAY

latcrthan

OTHERS

CONTAINED

DAMAGE

OR

INCIDENTAL

TO

ANOTHER

T HE

EXCLUSION

TATION

THIS

THE

OR

WARRANTY. THE WARRANTY
USE

OF THE PRODUCT. REP AIRS AND

ALL

and

with

HA

VEOTHER R1GHTS

ninety {9O)days after e)(piration

IN

PRODUCT

EXC

LUSI

CARRY

no

obligation

THI

S MANUAL

S

DAMAGES RESULTING

O R LIMI

ON

ONLY

WHIC

OR

PRODUcrS

TATI

MAY NOT APP

THE

UNEXPIRED

\0

make

corrcsponding

H VAR Y FROM

of

the warranty

ONS

IS NOT

3/

OF

LY

88

The infonnation

or variations of theequipmenl. N

installation, operation or maintenance. If you

manual, please

furnished

contaCt

the

in

Cro

this manual

....

'Tl Interr.ational Customer Services Dcpanment.

does

or

does

it cover every possi

Crown International, Inc.

1716 West Mishawaka Road
Elkhart,

Indiana 46517-4095

Phone: [phone]

Fax: [phone] F

Twx;

[phone]

WARNING

nO(

need

include

special

all

of

the details of design.

ble

situation

assistance.,

AX

whi

ch

may

beyond the

production,

arise during

scope of (his

TO PREVENT SHOCK

DO NOT EXPOSE TO RAIN OR MOISTURE!

CAUTION

TO PREVENT SHOCK

PLUG OF THIS UNIT WITH

CORD,

RECEPTACLE

BLADES CANNOT BE

DO

OR

ATTENTION

POUR PREVENIR

cenE

PRISE

SAUF

FICHE POLARISEE AVEC

DE

51

LES

EN

LES

CHOCS ELECTRIQUES NE PAS UTILISER

COURANT

LAMES

LAIS

OU UNE AUTRIE SORTIE

PEUVENT ETRE INSEREES A FOND

SER AUCUNE PARTIE A

OR

FIRE HAZARD,

NOT USE THE POLARIZED AC

AN

llliPOLARIZED

EXTENSION

OTHER OUTLET WHERE THE

FUL LY INSERTED.

UN

PROLONGATEUR.

DE

DECOUVERT

UNE

COURANT,

SANS

.

9

~(j'@llilllOll

_____

-"o

-,--

z"-,

'-'PO:::WE=Rc:.A"M

"-

PL"'IFc:IE"'R-'----

_________

---"'RE"'V'-".

0

Table

1 Introduction

1.1 TheD-75 ..................................................... 1-1

1.

2 Warramy

2 Facilities.

3 Required Test

4 Maintenance ...........................................

4.1 Safety First ....

4.2

Inspection

4.3 Disassembly ...

4.4

Reassembly

4.5

Troubleshooting ........................................... 4-2

5 Voltage Conversion
6 Circuit Theory_

6.

1 Block Diagram Circuil Theory ....................... 6·'

6.2

Balanced/Unbalanced Input Stage ............. ....

6.3

Inpu

t Operational Amplifier ........................... 6-2

6.4

Signal Translator ............ _ ........................ .. .. 6-2

6.5

Fi

nal

Voltage Amplifier .................. ..............

6.6

Bias ..........................................................

6.7 Output

6.8

Pro

tection Circu

6.9 I

{)Cn.I

6.10 Sig

nal

___ . ___ . ______

..................................................

___ . _____

.............................................

...................................................

..............

................................................. 4-2

Stage ............................................... 6·3

itry

(InputlOutpu(Comparator) ..................

Prcscnce

Ind

.

___

._._.

__

..

_._ ... _ .

....

_._._

... _ ..................

EquipmenL

................ . ........ .

___

._._._._._._

..

_._._._.

_________

..........

.............

ica

.. ..

....................

tor .............................

... _ ..... _ ......

...

_.

_._._._._._ 6-1

of

..

__ . ____

I-I

",1-

_._

...

_._

2-

3-1

4·1

4-1

4-1

....

4-\

___ . ______

5-1

..

6-2

6-3
6-3

6-3
6-4
6-4

Contents

7 Specifications

7.1 Gen

,1

7.2

7.3

7.4

1

8 Schematics

9 Parts._

9.

9.2 Standard

9.3

9.4

9.5 Te

9.6

era

l .......................................................

Monaural, ...................................................

Stecoo

......................................................... 7-2

PcrfonnanceGraphs ...................................... 7-4

....

....

1 General

Ordering P

S

Infonnat.ion

and

aIlS

hipm

ent

....................................................

nn

s ......................................................... 9- \

lIlu

SU'atcd

Parts Lists .................................... 9-2

Appendics A: Installallon.

A.

I

Mo

untin

g ........ .............................. ............ A·I

A.2

Wiring

.......................................................

A.2.1

SLCrco

........ .............................................

A.2.2

Monaural ................................................

A.3

Input

.........................................................

A.4

OutpU

I.

......................................................

A.S

Load Potcction ...........................................

Appendics B: Operation

B.I Precautions ........... ......................................

B.2

Controls .....................................................

B.3

PrOLCction

B.4

Fuse Rcplacemcnl .......................................

___

...

....

_.

__

._._._._._._.

._

..

_._

... _ .. _ ....

.. _

....

__

........ _._._._

......................................

Special Parts

..............................................

__

...

..

...

..............................

___

.......... _ ...

.................................................. B· I

_____

___

..

______

___

._._._

._

..............

._.

_____ 7-1

._

... _

...

... _ ... _ ...

_.

___

._._

...

7-1

7-1

8-1

9-1

9-1

9-\

9-1

9-\

A-I

A·I

A-I
A-I
A·I

A-2

A·3

8-1

B-1

B-1

B-2

ill ustration

1

.1

0·75

...................................................... ..

2.

1 Front Facilities (0.75) ................................ .

2.2 Rear Facilities

4

.1

2 Ohm Load Wavefonn ............................. ..

4.2

10KHz Square

.3

20KHz Sine

4

1M

4.4

4.5

Distortion Test Se(·up .. ........................ ..

Signal

5.1

AC

Mains Voltage Conversion ... _ ............... ..

6.1

0-

75

Block Diagr$l ................... ............... .

6.2 Balanc

6.3 Input Operati

6.4

Signal

6.5

Final

Voltage.Amplifier .............................

6.6 Bias, Output

6.7

IOC ........................................................

6.8 Signal Presence Indicator ..................... ....... .

7.1

Power

7.2

Nominal Frequency Responce ... ..................

7.3

Nominal Output Impzdance. ....................... ..

7.4

Nominal

7.5

Nominal Power Efficien

7.6 Nominal Damping Factor ..........................

7.7

Nomi

nal

7.8

Nominal

7.9

Nominal Noise Spectrum ............................ .

0-

75

8.1

9.

1

9.2

9.3

9.4

9.5

9.6

9.7

A.1 0-75

A.2

A.3

A.4

A.5

A.6

Schematic Diagrams ........................... .

0-

75

Main

Output
D-75

Front

0-75

Neon

0·75

Back
D-75 Capaci
D

-75

Final

Input High
InpUi
Wire

Gauge

Connection

Fuse

Nomograph

(0·75) ............ ..................... .

Wave

.................................. .

Wave

..................................... .

to

Noise Test Set·up ........................ ..

ed

Input

Sta~e

................................. .

onal

Amplifier. ..... .................. ..

Translato

Matrix

Module<

Mounting OimentiooS" ..................... ..

Low Pass Filter ................................ .

r .............................

and

Protection Stages.. ............... 6·3

..........................................

Phase

Respon

ce ........................... ..

cy

.......................... .

Output Phase Angle ....................... .

Crosstalk. ..... ... ............................ .

Modules .................................. ..

......................................... .

Pan

el Assernbly ......................... .

Bracket Assembly .................... ..

Panel

Assembly ................ ......... .

tor

Bracket

Assembly ................................ ..

Pass

Nomograph

to

an

Asse

mbl

Filter .....

Inductive

.......................... ... ......... .

.. ..

....................... .

............................ .

Load.

...

......

y ...... ......... ..

...... .......... ..

..

..

..
..

..

,

.,

2·'

2·2

4·)

4-3

4·)

44
44

5

·1
6-1
6-2

6·2
6·2

6-3

64
64

7·)

74
74

7·5
7·5

7·6
7·6

7·7
7·7

g·l

9·2
9·9

9·11,

12

9·16

9·17

9-19

9·20
A·I
A·2
A·2

A·3
A·3

A4

.3

, I3

This

Page

left

Blank

Intentionally

~RE~Vcc.

O'---

_________

-'O"'.

1 Introduction

Thi

s manual contains complete service infonnation

D-

75

Crown
conjunction wi

so

me
Manual
availabl

NOTE: THE INFORMA n

INTINDED

TECl-II\

1.1 The 0-

The 0

es

igned

d
amplification
distortion, the unit features balanced inputs, signal
presence

and a means

gro

und

power amplifier. It

th

th

e 0 -75 Ins

imponam

in

e.

'lClAN

informaLion

case the Ins

FOR

USE

ONLY

truction

75

-75

amplifier is a compact.

for

professio

from 20Hz-20KHz with

and

i()C1'loi

for iSOlating

.

nal use.

indicators,

BY

!

is

ttuction

is

duplicated
Manual is

ON

IN

AN

EXPERIENCED

aud

Providing

monophoni

elec

lrical

designed

THIS MANUAL

ground

10

Manual.

in

not

io

JX)wer

medium

minimum

c capabi
from

thi

readily

7"',"-P"O".WE"R"A"'M"'P"'U"FI"'ER"-____

Fig.

1.1 0-75

1.2 Warranty

on Ihe

be u

sed in

However,

s Service

IS

ProdUCt !.ha

an Auth
Factory

warranly policy should be directed to the attention

Technical Service Depanment

l

orized

Service Depanmenl. Any questions concerni

Crown

amplifier

power

lity

chass

is

(SU'©JMDIfil9

is

covered

Crown

1718

Elkha

by

warranty

Service Center or at

at:

International

W.

Mishawaka Road

rt,

Indiana 46517·4095

Phone; [phone]

FAX, (219 1294-8329
Twx: [phone]

mus

t

be

Se

the

, Inc.

rvic

ed

Crown

or

by

ng

Introduction

1-1

I · •

..

•

crown

D75·

• I

F C

2 Facilities

A. Power

The

AC

powe

r swilth, mounted at

of the 0 -75

AC

powe

irw:licato

B.

Power Indicator

Amber

C. Level

Th

e level of each ch

these controls.

do

wn and not u

D.

IOC

An

InputlOutpul

channel.
there
output s

is

a s

r switch is

r should

indi

be

cator thai the unit

The

sed

'"

Ill

umination

is

too

high

tag

e clipping or even

imple 2 position

po

on (8).

annel

control

when

Comparator

may

an

input level, improper

DE

E D C B A

FIG.

the ri

ght-hand comer

"on/orr' control.

sitioned

at

"on",

the

powe

is

on.

is independently controlled

for chan

opera

occur at such

nel 2 should

ting in MONO

LED

is provided

Lim

an

amplifier based

es

load

2. J FRONT FAC/LlTfED (0-75)

E. Signal Presence Indication

A sig

nal

presen

channel to i
orr'

with signal Jcvcl

state o

ndi

rlh

F. Output Monitor

If the

r

A standard

panel.

It is in parallel

be

used

to

1/4

dri

G. Output Binding Posts

Dual

binding postconnectors

eac

h cha

nnel. Use

cables

for

connection to thcjacks.

by

be

turned

mod

e.

for

each

as when

impedance,

probl

em.

only the t

H. Dual-Mono

Slide

10

mod
not

be

wO

this

switc

lhe ri

ght (eh. 2)

e

the

input and level con

be

used

and only balanced (ungrounded) loads

connected 10 the outp

ce

indi

cat

ion

cate

whe

n signal is presenl Unl

e I

OC

indicators

inch stereo jack

with

the main outputs

ve

headphones. -

dual banana plugs

top

jacks (red) are used.

h to

the

left (ch. I) for MONO

for

Stereo

ut

jacks.

LED is provid

the

is

provided

arc

provided at lhe output

In

mode

trol

for c

ed for each

SP)

LED's

on the

on lhe
brid

ged· MONO,

operation.

ham

'ICl tw

(0)

spe

ike

the

will

vary

fron

and can

aker

mode

In

MONO

o should

sho

"onJ

t

of

and

uld

2·1

Faci

lities

REV.

0·75

0

POWER AMPLIFIER

N L M

I.

Ground Barrier Strip

Isolation of chassis
accomplish

ed

tenninal strip. This
c

aused

by

"gro

from chassis

ground

by removing th

may

help

und

loops." (Circ

ground

by

2.7

from

signal
e shoning
rem

ove

uit

ohm

s.)

ground

strap

any

ground

FIG.

hum

is isola

2.2

is

easily

from

problem

ted

G

Rear Facilities (D-75)

L. Fuse

The

thi

s

s

lOOVAC

if

SC

I

is

used. The

warranty

K J J K

AC

line is safelY

or 120YAC operation.

up

for

200V AC.

use

of any oth

H

fused.

220V

AC

er

If

the

or

fuse v

a 2

unit

is

configured

amp

fuse

240Y AC, a 1

alue will

invalidatc the

is

used

amp

for

and

fuse

J. Input Phone

An

unbalanced
inpul o( each channel.
c

hannel

2 in

MONO

Jack

1/4 inch phone jack is provided

~

use

thc input jack

mode.

K. Balanced-Input Receptacle

A balanced
each channe

XLR

l.

con

nector

is

provided

at the

at

for

input

the

of

M.

Power Cord

A s

tandard

thr

ee-

wire

(gro

unded) AC

plug are provided

N. Serial Number Sticker

cord

with

Facilities 2-2

a 15

amp

This Page l eft Blank Intentionally

3 Required Test Equipment

Many

of the service and repair problems with the D·

can be performed with a limited amount

of

test

75

in

order

10

return

equipment. However,
"factory
test
co
of

new"

specifications.

equipment

lumn

is

provides information

recommended. The "Requirements"

the

fol

to

allow intelligent selcctin

substituleS if the "Suggcsted Supplier and Mode'" is

not available or is considered impractical

the unit

lowing list ofrequircd

to

obtain.

to

its

Equipment Requirements

Oscilloscope

Volt-Ohmmeter

Capable

IOMHz

Low-voltage resistance probe

lOOmv

of

displaying a

signal

(range). High-voltage

resistance probe

Frcq. Counter

Signal Generator

Circuit Breaker

AC

Mo

nitor

Line Vol

tag

Sine!Square

flat

frequency responce.

TIlD .1%

15

ampere rating

e

Peak:
rms

equivalem to a

wave

maximum

reading meter (displays

sinusoidal peak for any
waveform)

(I.5V range)

available;

Application

Monitoring output during

service and

testing

Check resistance values

(low voltage probe). Check.

semico

ndu

ctor junctions

opens

or

shorts (high

voltage probe)
voltages

Check

DC

For accurate general

Su

Telequipmcnt
equivalent

Auke

for

Heath

monitoring

Prov

ide

teSt

signals for

service and checkout

In

AC

line to

unit.;

proteCtS

circ

uitry from

ove

rload

Wavctek

equivalent

if

power supply has shorted

Monitor Line voltage Circ

Crown

ggested Model

D54A

8024 or equivalent

SMI18A

130

-Series or

uit

available

from

or

R9qired

Test

Equipmefll

3·1

This Page Left Blank Intentionally

REV.

D-75

0

POWER

AMPLfFIER

7

4.

Maintenance

Effective repair involves three basic steps:

the symptom(s) of the problem; 2) Identify

me

symptom(s);

caus.e(s), Before proceding through these steps

recommended that
in

the next section

unit.

4.1

Safety First!

To avoid risking electric shock, turn off and unplug the

from

D-75

disassemble or reassemble

If the unit
capacitors will probably have enough power stored within

em

to present a shock hazard to

th
circuitry. To safely discharge them, place a
watt resistor across the +

for

several seconds.

discharge resistor-particularly avoiding

the leads while dischargi

A

void

risk of

plugging the defective amplifier
has a 15

3)

Repair the unit 10 eliminalC the

you

first observe the

and

conduct a visual inspection of the

the

AC

power outlet before attempting to

it

has

been

in

recent

and

Usc

caution wh

ng

fire

hazard

from

amp circuit breakcr.

safelY

usc,

the large power supply

you

ana theampliiler

- terminals

me

capacitors.

shoned power supplies

imo

of

en

handling the

skin contact

an

AC oullet which

rem

10

Determine

the

cause(s) of

it

is

highly

precautions

10

ohm, 5

each capacitor

with

by

4.2 Inspection

A careful visual inspection
which you
remove t

Begin the inspection
appears abnormal. like broken wires and burnt or visibly
damaged components. Check wire and component solder
joints. Inspect the

traces

spend vi

may

encounter. To inspect the amplifier,

he

cover panels

prinlCd circuit board(s)

and

loose connections.

suaUy

inspecting the amp

by

is

valuable

as

described

looking

Be

for

most

in

section 4.3.1

for

anything which

for

thorough- the l

is

time

well

problems

broken

ime

spent.

you

4.3 Disassembly

The

eXlCnt

of disassembly required will depend
extent of inspection. service, testing, adjustment and
repair to
parenthesis are located
manual.

4.3.1. Cover Removal

A fairly complete visual inspection can
removing the top (91) and bottom (90) covers.

be

performed. Hlustrutions referred to

in

the parts list (Section 9) of this

be

upon

in

performed

To

me

by

remove

I.

mounting screws that secure
covcr

2.

secure bottom

upon

3.

pa.

4.3.

The
Probably the best

arrays (with the exception of one ground wire which

To

Lhcsc

pans, proceed as follows:

Re

move

lhe

eight rfour per side) phillips hcad

tOp

cover (91) . Gently lift

up

and

removc.

Remove the nine phillips hcad mounting screws that

COver

(90).

COvcr

will easily be removable

!;Crew

eXlJ"action.
Remove each
"lcl

components.

2.

MaIn Board

D-75

the

Main

through

soldered).

I. Refer to the component s

2. Unsolder

3.
throughout the underside
locations

4. Remove the four mounting screws

(33) located

board

5.

effortlcssl

4_3.3.

The D-75 Output Module should not have

unles~

is
below. A
Module
boa:"d.
disassembly instru::tions.

Removal).

transistors (25)
(two on each). Note:
spacers located beneath each screw!nut combinati

jar the position of spacers located

eimer push-on terminals or through

rem

ove the Main

Disconncct

up

All

work

Output

the

the case, refer to

This procedure

I. Replacement

leave the 0-75

and

note

rack

car (93)

Removal

has

been specially designed for

ex.ample

Board. Note that

Board

and

remove the black wire marked "ground".

me

15

color-cooed push-on wires localed

arc

marked

on

and

needed on this board may now

y.

t>oard

ll

other components on or around the Output

may

a.

Remove

b.

Unsolder

c. Removc the four driver transistors (24) screws.
d. Gently lift ooard upward, being careful

c.

Rem

location

f.

Replace board.

by

the

top

down

until

Modul

il~lf

the

be

replaced without actual removal

the

and

by

unscrewing the 8 mounting screws

In

in

its

normal/ying position-flat!!

ove

all

for

for

easier a::cess to front

ease

of service.

of this

is

the modular layout

all

connections are made

two 9 pin

proceed as follows:
id

e board layout, Fig. 6.7.

of

the main board. Their

wire color.

and

nylon spacers

side

of

the board. Gently

it

becomes

e

Replac

is

faulty

disa'is.embly instructions listed

is

also listedbclow, after the

Main

remove the

order to case replacement of

external wiring to Output Module

future ie-connection.

free.

emen

t/Repair

and

needs replacing.

Board (See Main Board

fou

beTICath.

Maintenance

be

performed

to

be removed

r Ourput

rock

of

on,

If

the

not

of

is

the

this

10

4-1

2.

Repair

3 .

All

component parts localcd

Module

removed

by

applying standard soldering!

may

be

desoldering methods (See Section
board.

Use

extra

care

when working

near

the

front panel so

b. Front

replaced without removing the

the

following section).

3.

Output transistor replacement-Output transistor (25)

an

be

rep

c
outp
Note
3,2

4.3.4. Front Panel Pans Replaceme

As

be

Generally.

or

format

I. Input

removing

laced

ut)

and

unsoldering

as

per

e}{

ploded

1), and its position

previously stated, all front

replaced without Output Mod u

th

is

pan

of obsuucting components. A detailed inslruCtion
is

listed below.

leve

l control removal is accomplished

the al

(20). Channel one pot can

as

not

panel controls

by

removing

the

view

in

assembly.

operation

uminum

is

knobs (28) and related hardware

to

OutpUt

two

twO

drawing

panel

performed

be

pulled

on

the

Output

7)

from

the

lOp

with

a pan localed

mar

the finish.

and

LED's

may

Module Board (Sec

mounting screws (per

main

connecting

ins

ulating wafer (TO-

nt

componcm pans can
le

removal.
by

unsoldering

back

and slid out the
left-hand side when the headphone jack (15) and
assoc

iaLed

hardware

sh

ou

ld

be

removed). Channel
pOlentiometer
R232

is

disconnected and the grounding bus strip
moved away
may

need

considerable,

to

come fr

ee.

2.

10C.

Sig

nal L

of

the

one
necessary

fou

in

order
Unsolder leads
needle-nose pliers, remove the
behind the

LED.
pulling straight back and removing
Replace the LED and reverse
installing

be

an

LED always observe correct polariI

helpful when inserting the rear
apply pressure
to

move

up

the

3.

On/

Off

Switch Replacement To replace

panel

OfI/off

switch (35) remove aluminum knob and
related hardware (27. 2,10, II
screwdriver, slowly pry orr
adhesive. Push switch
Remove wire. and slide the switch to the right
end.

Rep

lacement

necessary

to

replace the adhesive s

is

remo

ved

(10,

tWO

input level

can

be

rem

ove after

from the working

ED

Replacemen

area.

but gentle

pressure

t. When

r panel LED's (22, 23),

10

achieve a success

of

LED

10

be

replaced. With a pair

black

Nex

t carefully extract

of above.

bla

with

a 1/4

ft

nut

driver allow

middle

of

the dri

ver

).

With

fuse

bkx:k

back

until

solder lugs are exposed.

is the reverse of above.

14)

(rack ear (93)

the

"right" l

ead

The potentiomeler

in

order

hand

e}{trcme

suppon

ful

the

care is

repair.

ring

faulty

from the reat.

Note:

When

ck support ring

ing

(See Fig. 7.17).

the

a small

Oat-head

holder

from

and

Note:

trip

located beneath the

of the

be

pin

s.

all

by

of

is

for

ling any

of
located
LED

Y!

It

may
to

the leads

front

out

It

may be

fuse

block

.

4.

Neon

"Orr-On" Indicato r Replacement. Because

the

special mounting procedure u
power indicator (42), Crown recommends factory
rep

lacement only.

4.3.

5.

Back Panel Parts Replacement

All component
75 can

be
exploded view drawing,
quc.

..

tion

parts located

rep

laced

with relatively l

rear

on the

pane

s arise eontact the Crown Technical Service

Department.

4.4 Reassembly

Reassembly
doubt about t
appropriate illusuation

is

essentially the reverse

ypes

and sizes

of

attaching pans, refer

in

Section 9

4.5.Troubleshooting

Th

it

by

the

e three steps

were

mentioned earlier. They ean
three following questions: What
What

is

10 eliminate the cause (repair

section is
manner.

Finding
maintenancc. The
amp

lifier
specifications after
procedures
aid

you

4.5.1

Identifying Symptoms

Why

was the amplifier brought

it

10

malfunction again? (Some problems can
intcnniu.ant and diffic
anything

the

owner

some

other component

faull.

(Appendices A and B contain

opcmtion instructions

yo

u lack s

If
there isn'l anything obvious
sectio

n and procede dircctJy to the test procedures in
section 4.5.2.
meets factory
warranty coverage,
Departmcot.

to

effective troubles

causing the

to

and

probl

help

you

fixi

ng

the problem(s) is

final

to

be

certain

it

ha

in

section 4.5.3

in

locating the cause

wrong

with

the amplifier, tactfully inquire

used

it and try

ufficient

infonnation about

Using

it

specs.1f

please cal l Crown's Technical Service

em (cause)? What

)?

The purpose

answer

these

step is to thoroughly test

that

it

meets

..

been

repai

will help

of

problem(s).

in

uilLQ

fmd.)

10

detennine if it

in the

ir

syStem could

for

the

0 -75.)

wrong skip

can determine if the amplifier

you have

any questions regarding

sed

with

the

front

back

pane

l of the

ittJe

effort (see

l assembly). Should

of

disassembly. If

hOOl.ing

and repair

be summarized

is

the problem (effec!)

can

be

of

this

questions in

not

the end

an

of

the

th

e

faclOry

red

. The test

you

do this

as well

for repair?

If

yo

Can

be

u don't observe

was

mi

have

the installation and

the

problem and

to the next

of

panel

0-

in

10

the

in

the

?

done

orderly

as

you

get

how

sused or

been

at

4-2 Maintenanc9

"RE",V,,-"

O"---

_______

4.5.2 Test Procedures

Test

or

Adjustment

I. Quiescent

OC

offset

_ _

Input Signal
Characteristics

None

--'D'-

":.;:

'5"-P-"O"WE"'R.:.:A"'M:::.P.=

Ll

F

c.:

'=ER"--

____

Instructions/Comments

±

lOmV

(£(j'@Qd1!)(flJ

(3

adjustment

2. Bias

3.

Power (single channel)

4.

Prot.ection

5.

High

Circuit

Frequency

%

None

1 voit;IKHz

sine

wave

1 voit;lKHz

sine wave

I vol

t;

10KHz

sq.

wave

I voit;lKHz

sq.

wave

Positive output, base-emiuer junction should

.3V and .35V. Adjustable by

Into 8 ohms,
before signal clip.

InlO

4 ohms,

before

Int

o 2

Into

ar\ 8 ohm

sig

nal

Into

an 8 ohm

exhibit no ringing (see Figure 4.3).

20

vrms (SO

11.5

vrms

signal

cJLp.

ohms,

signal

load, a

should exhibit

load, a 19vrms

will

no

(75

appear

25

RIl2,

watts)

should be obtainable

walts)

should

as

in

volt

peak

to

ringing

(see

sine

wave

R212.

Figure 4.1.

peak:

figure 4.2)

, ,

!

be

be

obtainable

square

signal sh

between

wave

ould

-

Rg. 4.1 2 Ohm Load Waveform

Fig

. 4.2

-

I.

Il'

•

10KHz

Sq.

Wave

Fig.

4.3 20KHz

Sine

Wave

Maintenance

4·3

9 (£(f'@(hMUll

____

_

--'O;:.."'75"PD="''''E"R."AM=PL"

IF"

'E,,R'-_ _ _ _

_____

---'R'''E,.,V'-''

. 0

Test

or

Adjustment

6. Inlcnnodulation Distortion

7.

IOC

8.

Signal

to

Noise

9. Quiesent

AC

Power

'IO"~

I<.

~

VOlNErt

Input Signal

Ch

.

SV +/·

7KHz signal

s

ummed

ratio

2.5V peak.peak

5Hz

T

~

.-

aracteristics

2%: 60Hz·

in4:1

sq.

wave

Instructions/

(

See

Fig. 4.4) When using the Crown IMA, typical

reading

OdB·.OO4

-SdB

lhrough

s

will

%

COmments

be

as

follow

-25dB=.03

s:

%

·30dB·.03%

OC shou

every

rator

See

Fig

OUtput

IS

walts at idle

1

20

watlS

I

03%

ld

illuminate

fall time

rise

(twice

lime must

. 4.5) SignallO

with

meter

as

monitored by wattmeter

at full

rated outpu

~

~

~

~'.

once

for

every

every

full

be

l

ess

man

noise should

bandwidth

t.

I

rise

cycle), Test

1.0

be

of

20Hz

·3SdB·.

I

for

gene

(

rated

time

and

microsecond.

1

000B

below

to

20KHz.

on

AC line;

once

."

r.::EL~TI\Ol

INPUTS

I,"","IOU"1

D4$CQNN«:I( O)

~

,-

(l<

AHHR

I

J:.~

I

~

~,

~.-:;:.

,

Fig

.

4.4

1M

Fig.

4

.5

Signal to Noise

I~

Distortion

IIE!\IIM I,NlIICIUN()£()

AAO.INO

QUl'NT

/'

...........

I

Test

Set-up

res

l Sel-up

CA&(

WlW'PE

h

D

OM

~wm

{~l

TH(A

C

IWI'<IE

••

L

4-4 MaintBnanc9

A

~E",V"-."-O

__________

5 Voltage Conversion

--,,D-,.75=PO::."':.:;E",R.:.;

A

o:M:::P-,L::..'F,,IE.:.;R

_____

(£[J@(1ill)1fil9

Often Crown
later moved to another requiring

For

this

a

world-wide

The

0-75

vo

ltages. Convening
accomplished with a soldering
cutlers. Follow the

the

drawi

CA

UTION:Because

only a competent technician should attempt to alter
tbe line volta ge

1.

Remove the

sc

rews).

2. With
you, locate

hand comer.

3.

Make

desired operat

4. RepIace
fu

se.

for all connections 200V

5.

Change

produCIS

reason

voltage

power

ng

below.

the

unit right si

lhe terminal strip on the

the

appropriate change

ing voHage.

the 2 amp

the

line cord tage

are purchased

the

following chan/explanation

map

is

supply

may

from

fable show

there

co

nfiguration.

tOp

cover of

de

up, and the front panel toward

See Fig.

line fuse with a I

in

one country

an

AC

mains

provided.

be

c

onnected

one

1.0

another can

iron

n with

is

a risk

the

D-

75

in

and

10

read !he correct voltage.

for

and a pair of

the schematic,

of electric shock,

(held

on

front

in the near right-

jumpers

7.30.

above.

amp

for

type

and

conversio

as

well

any

of

be

wire

and

by

8

the

3AG

as

five

n.

100 VAC

r~

II

~

¥

~

~

~

200 VAC

&~~~~

220 VAC

Note:

Use
operation.
or 240V

only a 2 amp fuse for

Use

AC

operation.

only a 1

amp

lOOVAC

fuse for 200VAC,

or 120VAC

220VAC

~l~~~

z w

tf

o

Rg.

5.

1 AC

240VAC

Ma

ins

Voltage

Conversion

Maintenance

I-

~

5·

t

This

Page

LeN

Blank

Intentionally

REV. 0

0-75

POWER

AMPLIFIER

6 Circuit Theory

6.1

Block Diagram Circuit Theory

The following
Fig.

6.1.

When

using the

out

of

phase,

circuioy.
become
circuitry,

will

Here, the

the

Unbalanced

cliscussioo ref

XLR

Balanced

be

introduced 10 the

two signals

o

utput

ers

lO

the

Input.lwo signals, I

arc added together

of

the

~

In

P:trz;

UNBAl

INPUT

CH,

block

Balanced

Balanced

pbue

. ,..;,t,

diagram

Input

to

input

1M

•

i9UI

in

SO°

00QUII1O

Thiscombincd sign
amplification
amplitude to

A ponion

Presence cin:uilry. Provided the output
amplitude
s

ignal

with

The output
i

npu
two
amplifier

The Powe
various

of

of

prese

Lilc OUlPU

signai
t signal. Any n
signals

and

r Suppl)'

circuit

POWER

A

MP

CH

1

al

is then

where

it

is

boosted

drive

an Out

put

the

output signal is

at least one

nce

indicators willlighl

L si

will

generate a correction

the

componeOis

vo

gna

l.

is f

ed

back

onl

ineariti

JOC

indi

supplies the

cators

fed

Load.

ll

peal.:

to

a.'ld com

es exi

proper

within

to a s

to a l

routed

to

and

sti

on

the

the

tage

of

eve

l of s

to

the

sig

nal

peak, the

vary

pared

ng

between

signal

to

fronL

voltages

amplifie

powe

ufficient

Signal

has

J!l

green

in

imensily

with

th

th

e

panel.

to

the

r.

r

Lile

ese

3AlINPUT

AC

BAlINPUT

LINE

UNBAl

INP

UT

CH2

I

I

POWER

SUPPLY

F

ig.

6.1 D

r8

~

POWEM

AMP

CH2

·7

5 Block Diagram

s~

MONO",

SWITCH

I

s~

,-d'

MONO

Lf\-

Circuit Theory 5

-1

~

If:::(f(g)(Id!!)(fj) _

____

--'D'C-'-'75'-'PO~W!"E":'R~A""M":P,o,L1F':"=cER~

___

_

______

~A!OEV~.

0

The

following explanation refers
MI-270b
theend
discussion

familiarization. Only channell is shown

located

of

Section
is

in the

9.

reprinted

In

struction

How

below

10

schematic

Manual

ever, each circuil

in

order to aid

for

as

under

in

sim

diagram

well

as

circu

pli

city.

it

6.2. Balanced/Unbalanced Input Stage

In

order

to

eliminate

inp

ut

(as

well

the 0-75. U2A

which provide
balanced input design.

input signaJ, an

inverting

and

degrees out

unbalanced

but without any annoying noise
present at

unlik
(by some
balanced line and
output Note

(-)

3). This

of
and in phase

the

e

the

aud

c:\temal source)

and non-inverting (+) inputs

has

annoying

as unbalanced) stages

and

U2B

the

correct phase

input

from

the

effect of driving the inputs J

phase.

1be

input. The reason

io input signal,

will

the following

RF

are

the

balanced input op amps

inv

As

per definition of a balanced

a balanced

output signal

with

the

signal

lIlal

for

the

noise signal produced

will

appear

cancel each other at

diagram.

interference, balanced

ate

iocorporalCd

ersion used

lin

may have

this

on

in

e is

fed

10

the

of

U2A

(pins 2

80

will

now

be

applied

10

pin

been

is

because

both sides oflhe

the

op

amp

al

in

3,

357, it acts
emcme1y
paths. The
two

lhcy

6) to
cntering

because of
output
output signal
diffcrence
voltagc divider,

as

an

input voltage amplifier producing

low

distortion

gai

n dctcrmining components

voltagc dividing resistors, RI03 and

act

as

a feedback palh

lhc inverting input of U

U

100

al pin 3 will

lhis

feedback path

(pi

n I) of almost

that

in

ohmic

RIDS

is

value

by

means

from lhc outp

100 (pin

be

zero.

prescnt

(with respect to

and

R103.

cIa,

25
N

:;

-l

.

~1O~

200PFT

R102

'K

± Rl04

7

10K

R'03

.

5W

'"

'"

0110

*

C~f

"

_ RIS1

- 9.

53K

'"

Fig.

6.3 Input Operational Amplifier

of

several feedback

for
RIOS.
ut

2).

Both sig

in

phase w

and

Thc sma

is

thcre because of

0109

ith

will thus produce

ll

amount of

:'f

~,

•

-

1~V

.~

RI52

OPEN

;

this

stage arc

Note

ofUlOO

each othcr

the

gai

n)

of

~

i'

that

(pin

nals

slight

C'06
27PF

R'08

toK

.5W

an

IDa

''''''''

el2S

82PF

Balanced

"',,"'

Fig.

6.2 Balanced Input Stage

6.3.

Input

The input op amp,
bandwidlh integrated circuit.

Operational Amplilier

UlOO

is a low

I 9.9K

9.9K

noise. large gain

Under its

formal

name,

LF

The

IC

op

amp

will

always try to keep a zero potential

difference between

will

cause the
lhcrfore a substant
retain

the

small output level.

OJ>

bolh

inputs.

Any

type

amp

to produce a large output, and

ial

size correc

tion

signal

of

non-linearity

in

order to

6.4. Signal Translator

The opcmtion of
through QI02) is to basically provide voltage
amplification. However, lhe signailfan
(QIOO)

provides
rather converts the ground referenced input signal to a
s

ignal

with
is highcr volta
Voltage Amplifier).

Fig.

the

D-75

front-end circuitry

no volta

ge

amplification itself, but

a reference to the negative supply. The result

ge

swing capabilities

3 Ul(l(l

>-,

--

6.4 Signal Translator

from

"'"

-ka,co,,£!

(IC

slatOf

transistor

QI02 (Final

C"r

r

"

op

amp

6-2

Circuit

Theory