Universal Audio 1178 Operating Instructions Manual

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TABLE OF

CONTENTS

PAGE

SECTION I;

1.1

1.2

1.3

1.4

1.5

SECTION

2.1

2.2

2 . 3

2.4 LINE

2.5

2.6

2.7

DESCRIPTION

SPECIFICATIONS

FRONT

PHYSICAL

CONNECTIONS

II:

UNPACKING

ENVIRONMENTAL

POWERING
EXTERNAL

IMPEDANCE

ACCESSORIES

2.7.1

2.7.2

SECTION

3.1

3.2

3.3

III:

GENERAL

INITIAL

PERFORMANCE

3.3.1

3.3.2

3.3.3

3.4

APPLICATION

3.4.1

3.4.2

3.4.3

3.4.4

3.4.5

3.5

PLACEMENT

3.5.1 AFTER

3.5.2

3.5.3

3.5.4

3.6

STEREO

INTRODUCTION

PANEL

CONTROLS

INSPECTION

AND

INSPECTION

CONSIDERATIONS

VOLTAGE

SWITCH

CONNECTIONS

TERMINATION

AND

MODEL
MODEL

301

SC-2

OPERATING

DEFINITIONS

SETUP

CHECK

INPUT-OUTPUT

GAIN

STEREO

REDUCTION

TRACKING

CONTROL

EFFECTS

EFFECTS OF
EFFECTS

EFFECTS

THE

OF

PREAMP

EQUALIZATION,

FULL

PROGRAM

PRIOR TO

OPERATION

-

ELECTRICAL

AND

ADAPTER

SECURITY

INSTRUCTIONS

SIGNAL

SETTINGS

COMPRESSION

OF

THRESHOLD

ATTACK

OF

RELEASE

OF

1178

BEFORE

MATERIAL

OUTPUT

INSTALLATION

COVER

LEVEL

CHECK

RATIO

TIME

TIME

OR

IN

AFTER

LIMITER

AMPLIFIER

THE

SIGNAL

LIMITER?

THE

PATH

1
2
3

4
4

5
5

5

6

6
8
8

9
9

10

H

11

11

12

12

12

12

13
13

13

14

14

14

15
15

16

16

-i-

SECTION IV:

THEORY

TABLE

(continued)

OPERATION

OF

CONTENTS

OF

PAGE

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

GENERAL

INPUT

VOLTAGE

SIGNAL

LINE

GAIN

METER

POWER

SECTION

5.1

5.2

5.3

GENERAL

REPAIRS
INTERNAL

5.3.1

5.3.2

5.3.3

5.3.4

5.4

5.5

5.6

IN

5.4.1

5.4.2

5.4.3

PC

CLEANING

AMPLIFIER

-VARIABLE

PREAMPLIFIER

AMPLIFIER

REDUCTION

AMPLIFIER

SUPPLY

MAINTENANCE

Vi

WARRANTY

AND

SERVICE

POWER

Q-BIAS

METER

GR

COMMON

DIFFICULTY

CASE

OF

GENERAL

PRECAUTIONS

VISUAL

TROUBLESHOOTING

BOARD

CLEANING

THE

RESISTOR

AMPLIFIER

ADJUSTMENTS

SUPPLY

ADJUSTMENT

ZERO

MODE

AND

REJECTION

FOR

TEST

LIMITER

ATENUATOR

TRACKING

TROUBLESHOOTING

TABLE

(FIG.

5-1)

17

17

17

17

17

18

19

19

20

20

20

21

21

22

22

22

22

23

24

24

26

26

SECTION

FIGURE

FIGURE

VI ;

6-1. MOUNTING
6-2.

APPENDIX

MODEL

DIAGRAM

INSTRUCTIONS

1178

DUAL

PEAK

MODEL

FOR

LIMITER

301

SCHEMATIC

27

28

SECTION

INTRODUCTION

I

FIGURE

1.1 DESCRIPTION

Model

The

1176LN Peak

stations,

Dual Peak

The

channels of

Limiter used

sound

Limiter was

program

audio channels

Model

sary

nels

adjusted

allows

together
amplitude
On

limiters

with

similar

utilizing

1178 are matched

for critical

Single

adjustments

simultaneously,

independently.

the two

such that

causes the

the other

hand, when

process

exceptional

Model

The

to the single

FET's as

permits severe

ratio

may be

structure

to-noise

optimized

throughout

ratio at

1178

1-1.

is a

MODEL

two

in many

reinforcement

material

must

be maintained.

to assure

stereo

applications.

of attack

while

In

limiters'

the

gain

audio signal with

same amount

switched

the signals

flexibility

1178

was

designed

channel

voltage

limiting

without

for

the

Model

normally

1178

channel

FRONT

version of the

recording studios,

installations,

designed

are processed,

the input

the

for those

The two

the high

and release time

and

stereo

reduction

of gain

to single

independently.

in operation.

to have

1176LN. Limiting

variable

resistors.

added distortion

various

used

program materials.

1178

maintains an

control

PANEL.

etc.

around the

applications where

and the balance

limiters inside

degree

of tracking

output level

mode, a front

amplifiers

larger

the

reduction

mode

operation, the

This

provides the

performance

is

Unique

and

excellent

setting.

very successful

broadcast

world.

two

these

of

the

neces-

affect both

chan-

controls are

panel switch

to be

linked

peak-to-peak

both channels.

in

two

user

characteristics

accomplished by

circuitry

compression

the

The gain

signal-

Dual,

either

referenced

meter

(VU ballistics)

reading

backlighted

amount of

the

to

+4

dBm or

characteristics:

or peak.

front

gain

panel

reduction, or

+8

dBm. Also

either indicating

-

-

1

meters

may be

the output

switched to

signal

switch selectable are

average

read

level

the

signal

.

.

1.2

SPECIFICATIONS

ELECTRICAL

INPUT

MAXIMUM

FREQUENCY

MAXIMUM

(Each

Channel):

INPUT:

IMPEDANCE:

INPUT

LEVEL:

MAXIMUM

RESPONSE:

OUTPUT:

OUTPUT

OUTPUT

LEVEL:

DISTORTION:

GAIN:

LOAD:

Balanced

20 kohms,

10 kohms,

bridging,

used as

used

(single-ended)

+20 dB

45 dB,

±1 dB,

Floating,

150 ohms

+24 dBm

maximum

±1

dB.

20-20,000 Hz.

transformer

or

into

+20 dB into

Less

than

limiting,

with

(as

low

of

faster

0.5%

at

all

frequency

release

balanced

unbalanced

as

input.

(Ref.

greater.

ohm

600

ohm

150

THD,

seconds

1.1

limiting

peaks

time)

differential

input.

0.775

volts rms).

isolated.

load

load

50 Hz

(12.28

(7.75

to

15

release

devices,

increases

amplifier.

volts).

volts).

with

kHz

setting;

distortion

with

SIGNAL

NOTE:

to

NOISE

TO

ATTACK

RELEASE

THRESHOLD

OUTPUT

Throughout

denote a

RATIO:

TIME:

TIME:

LEVEL:

signal

vs

this

level,

Greater

Hz to

30

than

15

Less than

adjustable

panel

50

maximum

with

control

milliseconds

(for

front-panel

Compression

Ratio

Setting

20:1

12:1

8:1

4:1

*with

a

manual,

output

reserve

where

it is

dB at

81

kHz.

microseconds

20

microseconds

800

to

minimum,

recovery).

63%

control.

Input

Minimum

Threshold

-24

-25

-26

-30

gain

of

control

approximately

expression

the

referenced

threshold

1.1

Level

Limiting

±2 dB

dB
dB

dB

dB

to 0

100%

for

with

seconds

Adjustable

at

to

set

dB.

10

"dB"

-

dB

0.775

limiting,

of

recovery;

front-

Relative

Output

at

Threshold*

+10 dBm

+9

dBm

+8

dBm

+7

dBm

provide

used

is

rms.

V

-

-

2

.

)

1.3

INPUT

POWER

FRONT

AND

LIMITING

REQUIREMENTS:

ENVIRONMENT:

PANEL

OUTPUT

CONTROLS

LEVEL:

ATTACK :

ON/OFF: This

RELEASE:

-

100

switch

VAC,

125

selectable,

Operating,

—

Storage,

20“C

Continuously

Continuously

microseconds.

800

to

maximum

the

switch is

with the

full

limiting

Attack

counterclockwise

function

Continuously

seconds

obtained

in

to

200

or

less

+50

0*C to

to

®C;

+60®C.

adjustable.

adjustable,

(Fastest

clockwise

coupled

Time

control.

disabled.

is

adjustable

1.1 seconds.

maximumum

the

in

-

250 VAC, 50/60

than

10 W.

20 microseconds

attack is in

(CW)

position

position.)

from

50 milli-

In the

(CCW) the

(Fastest

CW position.)

Hz,

release

-

A/B

STEREO

COMPRESSION

METER

SWITCH :

In the

operated

the

amplifiers

together,

channel

in the

ratio,

always

RATIO:

Switch

pushbuttons

FUNCTION: Three

the

gain

referenced

fourth

characteristic

the

VU

indication

+8

dBm

meter

to a

selected

(Gain

average

position

A/B

as

STEREO

position

of

and

causes

other

attack

identical

selectable

interlocked

meter to

reduction

to

pushbutton

output

level.

pushbutton.

reacts

level

which is

output

reduction

responding.)

independent

two

the

the

an

channel.

time,

in

read

or

+4

dBm or

of

selected

as

faster,

signal

indication

Model

the

gain

the

channels

two

maximum

equal

and

both

with

limiting

amount

(The

release

channels

four

pushbuttons

either

the

selects

the

the

output

+8 dBm.

the

meter

"Average"

with

In the

and

6 dB higher

"Peak"

VU

0

reference.

is

1178 may be

limiters.

reduction

linked

are

one

in

limiting

of

compression

time are

.

interlocking

switch

amount

signal

of

level

The

response

when

is

reading

typical

+4 or

the

mode

corresponds

than

the

always

In

the

-

-

3

.

.

.

.

1.4

1.5

POWER

PHYSICAL

DIMENSIONS:

SHIPPING

ACCESSORIES:

CONNECTIONS

SWITCH:

FINISH:

WEIGHT:

WEIGHT:

Toggle

Model

483

panel 203

Panel is

anodized

is

5

kg (11

6.6

Model 301 XLR/QG

and

switch with LED to

X

1178

89

mm rack

is

mm

powered.

panel . Depth behind

(19"

3.18 mm (1/8") brushed

aluminum in 2

cadmium plated steel.

lb)

kg (14.5

lb)

Adapter for signal input

output

Model SC-2 Security

Rear chassis

output.

Power through 3

barrier strip for

connector

3-1/2"

x

Cover.

indicate when the

8").

x

clear

shades. Chassis

input and

wire lEC-style

-

-

4

1

.

2 .

the

UNPACKING

Your

Model

container

Nevertheless,

carton

have

ial or

claim

and its

occurred

damage

If

carton,

the

damage.

for

shipment

The

Model

2.2

UREI

Two-part

same

INSPECTION

INSPECTION

AND

1178 was

designed

was

recommend

we

contents

transit.

in

evident,

is

and

Shipping

should

1178

Instruction

Warranty

serial

SECTION

AND

carefully

protect

to

careful

for any

do not

immediately

claims

include:

Dual

Peak

Manual

Card

number

as

II

INSTALLATION

packed

the

examination

physical

sign

of

destroy

notify

must

be

Limiter

(this

book)

bearing

Model

the

the

at

unit

of the

any

carrier

the

made by

the

1178.

factory,

from

the

of

damage

the

rough

shipping

which

packing

of a

consignee.

and

handling.

could

mater-

possible

Rack

ENVIRONMENTAL

system

2.3

temperatures

condensing

producing

should

while

from

to

tr ans

The

the

If

be

circuitry

moderate

avoid

formers

relative

equipment

provided

mounting

POWERING

The

250 VAC

Section

1178

mains (50

2.4,

panel switch.

SETTING

THE

1178 TO THE

THE

mounting

CONSIDERATIONS

will

from 0*C

operate

to

humidity.

installed

system

is

(such as

order

in

susceptible

electromagnetic

system

the

motors

,

may

the

BE

OF

nominal

SURE

THE

etc

,

operated

be

Hz or

TO

VOLTAGE

MAINS.

hardware.

satisfactorily

+50-0

(+32*F to

in an

power

assure

to

hum

to

fields,

immediately

from

single

Hz,

60

line

voltage

VERIFY BOTH

SELECTOR

122*F),

equipment

euntiplifiers

longest

pick-up is

installation

adjacent

either

100

phase.)

may be

ACTUAL

THE

SWITCH

BEFORE

over a

range

and up

rack

adequate

) ,

component

sufficiently

should

to

-

125 VAC

indicated

As

selected

LINE

CONNECTING

of

80%

to

with

high

ventilation

life.

shielded

be

or

power

200

a

large

with

VOLTAGE,

ambient

non-

heat

Also,

planned

-

in

rear

AND

-

-

5

comply

To

with a

is

three-wire

connected

ground—loop

significant

a

ground

and

installed*

of

the

ground

power

loops

cord

temporarily*

buzz,

or

aware

safety

a

actions

result

but is

that

hazard

or

from

with

the

to

problems*

potential

grounded

the

hum is

If

by

and

This

not a

unless

can

direct,

for

violation

most

style

lEC

chassis*

Ground loops

difference

metal

experienced,

using

mains supply,

the

ungrounds

substitute

Model

the

exist*

incidental

of

Electrical

connector,

some

In

enclosure

3—

prong

a

Model 1178,

the

for

1178

UREI

any

Dual

accepts

electrical

Codes,

the

installations

result

can

exists

one

to

between

in

may

2—prong

ungrounding

proper

Peak

no

consequential

or

codes*

1178 is

the

grounding

in

which

check

AC

and

system

Limiter is

pin of

this

hum

the AC

chassis

the

the

for

adapter

the AC

cure the

may

grounding*

AC

responsibility

damages

supplied

which

may create

and buzz

conduit

is

possibility

between

plug

hum

grounded,

for

that

if

Be

legal

may

2*4

LINE

Unless

Model

power

60 Hz),

position*

230

slot*

blo when

operation*

switch*

2*5

EXTERNAL

VOLTAGE

a tag

1178 was

mains*

slide

sure

Be

changing

A

Permanent

connected

cable,

and

indicated on

used,

are to

be

instructions

Instructions,"

Model

the

If

recommend

circuit,

with a

(See

we

620 ohm,

Section

SWITCH

on the

shipped

In order

VOLTAGE

the

The

change the

to

to 230

small

ready

to

voltage is

screwdriver

CONNECTIONS

input

the rear

install

suppplied

Page

and

accordance

in

panel

the

with

and

9,

1178 output is

shunting

watt

1/2

2*6 regarding

line

cord

for

change

operation

this

SELECTOR

visible

fuse

to the

V operation

should

output

signal

barrier

accessory

adapter*

the

Section VI*)

connected

the

resistor*

input

termination)*

specifies

nominal

for

switch

on

in a

correct

/4-amp

or

1

used

be

wires

with

standard

strip*

Model

(See

"±"

and

This

assures

otherwise,

with

nominal

the rear

window

value:

slo-blo

to

should

wiring

the

If

according

301

also

to a

"COM"

high

output

optimum

the

115

230 V (50

panel

next

to the

1/8-amp slo-
for

move the

shielded

be

practice,

XLR/QG

"Mounting

impedance

terminals

loading*

VAC

Hz or
to the

switch

V

115

recessed

as

connectors

to the

(See

Figures

recommended

for

2-1

2-2

and

connection

-

6

on

the

following

page

procedures*)

-

OUTPUT

QRD

INPUT

FIGURE

2-1.

CONNECTING THE MODEL 1178 WITH BALANCED

INPUT AND BALANCED OUTPUT

CIRCUITS.*

No

2-2.

special

FIGURE

*With

use

balanced input

a

the appropriate

diagrams.

CONNECTING THE MODEL 1178 WITH UNBALANCED

INPUT AND

and unbalanced output,

conhections

switching

UNBALANCED OUTPUT CIRCUITS.*

vice-versa,

or

suggested by each

or transformers are

of the

needed.

above

2.6

IMPEDANCE

.

TERMINATION

AND

Audio

"600

ohm

circuits")

Long

be

their

noise

only

audio

properly

characteristic

rejection

However,

unnecessary

broadcast

circuits

advent of

spawned

has

devices

engineering

circuits"

are

transmission

studios

are

negative

having

essentially

output

the

minimum,

(all

source

other

(lOK

(operated

output

Switching,

current

same

output

with

UREI)

at

impedances.

Most

modern

active

50K)

to

in

of a

patching,

"unterminated"

(ungrounded)

differential

minimize

into

ground

common

interconnecting

the

potentials

had

(together

carry-overs

lines,

sourced

from

impedance,

be

to

are

transmission

impractical

but

other

and

seldom

more

feedback

modern

indifferent

audio

source

impedances

to

inversely

voltage

change

no

have high

audio

devices

input

tandem),

impedances.

proceeding

bugaboos

into

in

input

systems,

which

or

device,

etc. is

are

transformer

transformerless

mode

noise or

roots

its

with

from

and

achieved.

line

telephone

like

terminated

if

theory

within

local

than

several

circuitry

amplifiers

of

load

to

impedances

changes

load

any

frequency

impedance

therefore,

have

very low
These

many

inputs

without

simplified

essentially

outputs

minimize

input

interference

wires

or

the

in

their

predecessors,

their

in

optimum

and

modern

audio

systems

hundred

and

other

and

only

load

in

impedance

response.

to

products

may

regard

because

eliminated.

circuitry

cables,

telephone

transmission

video

counterparts,

equipment

frequency

techniques

recording

where

feet

solid-state

signal

ohms.

few

a

varying

by

and

impedance,

above a

Most

allow

use

utilize

output

impedances

may

connected

be

impedance

to

"double

ground loop

input

(or

which

or

may

produced

industry,

"500

ohm

practices.

which

matches

response

not

are

studios,

transmission

length.

in

electronics

processing

They

are

their

maintain

rated

designs

new

with

various

amplifiers

and

cascaded

to

be

single

a

"matching".

thus

loads"

"Floating"

problems,

transformers)

induced

be

different

by

and

must

and

The

and

high

and

and

Where

more

of

line

termination

The

used

ohms

in a

when

device

high.

impedance

vacuum

1178

the

audio

than

Model

balanced,

used

suitable

Only when

termination

tube

equipment)

input.

must

several

practices

1178

unbalanced

for

it is

transmitted

be

hundred

feet

should

has an

input

differential

(one

use with

used

(such as a

is a

any

from

source

-

through

length,

in

still

impedances

input

side

grounded).

normal

source

a

600-ohm

termination

-

8

cables

however,

observed.

be

20,000

of

configuration,

This

source

which

impedance,

requires

transmission

resistor

or

wire

pairs

transmission

ohms

and

makes

line

when

10,000

the

low

low

a

or

required

or

older

at

ACCESSORIES

. 7

2

ADAPTER

2.7.1

MODEL

301

Two

rier

the

strip.

limiter

2.7.2

An

controls

misad

justment

holes

This

to

SECURITY

optional

the

of

of

provided

are

allows

signal

Security

Model

critical

cables

COVER

1178,

adjacent

simple

fitted

SC-2

Cover

and

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9

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3.1

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SECTION

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FIGURE

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MODEL

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with

the

designations in

rear

IC

1,

balanced or

panel

section A

unbalanced

either the

latter causing a

of input

trimmed

versus

with R1

1178

schematic

barrier

&

(IC

B

signal

terminal

COM

output

(RlOl), and

signal.

at

2,

VOLTAGE-VARIABLE

4.4
input

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through the

(R103)

as

limiting

gain
resistance

4.5

adjusted

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voltage-

the

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gain.

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the

low

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applied

ratio

amplifer

simultaneously

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LINE

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signal

consisting

components,

RESISTOR

signal is

Input

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series

element

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bring the

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R18 (R118)

amplifier stage

minimum of distortion

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FET.

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for

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high resistance.

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in the

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feedback loop is

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gain

output

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reduction

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provides

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output

control

amplifier.

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is

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transistor

threshold of

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signal is

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amplifier

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channel

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of

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and IC 7A.

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voltage

voltage

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dB

ohm

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compression

The

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S3.

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load

audio

Depending

in

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compression

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polarity is

resistors

R36,

R37 for

amplifier,

value

transformer

and

approximately

in the

REDUCTION

signal

Resistor

parallel

signal

developed

inverted

supplies

summed

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8:1

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designed

excellent

overload

output

AMPLIFIER

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position

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on

with

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junction

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at

amplifier

in

control

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for

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characteristics.

gain,

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transformer

through

threshold

the

of S3,

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wave

rectified

of

IC 7B,

voltage

with

set

value, a

input

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voltage

UREI

for

and an

when

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C31

for

different

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then

and

across

different

current

of

voltage

around the

from

assuming

phase

low

additional

terminated

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4:1

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resistors

threshold

negative

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and

CR5

drives

capacitor

resistors

opposing

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7B.

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divider R35,

a

shift,

amp-

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with

circuit

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a

7D

compression

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the

for

dc

CR6.

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transistor

C37.

selected

Corresponding

inverting

negative

During

timing

the

for

R42,

is

which

turned

tance of

limiter.

neglected.

mine

the

When

increasing

tionately

audio

two

signal.

limiter

The

part

is

tion.)

input

of

A

of

generated

conduction,

capacitor

Attack

the

is

discharge

off,

R43.

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the

too is

It

discharge

The stop

fastest

the

attack

voltage

positive

into

conduction,

During

channels

gain

reduction

Attack

the

sufficiently

IC

by

effectively

7,

rectifier

the

transistor

C37.

Control

variable,

the

resistors,

and

across

value,

the

thus

STEREO

connected

are

function is

Control

large

overriding

circuit.

Q3

The charging

of

C37

of

and is

relatively

R44

release

is

C37

control

providing

operation

together.

and is

positive

functions

limiter.

the

occurs

the

small

R45,

and

time

zero,

of

no

voltage

a

the

disabled

engaged

current

negative

any

as a

time is

through

Release

value

are

unit.

the

limiting

drives

voltage

control

with

the

in

is

current

variable

When

transistor Q3

large

the

Control

of

selected

occurs.

FET

divider

voltages

switch S5.

full

driven

dc

into

voltages

R42

to

Q7A

CCW

source

with

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of the

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With

propor-

for the

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the

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4.7

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allows

R27

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AMPLIFIER

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R50,

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in

characteristic,

5A.

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+8 dBm

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reading

constant

ponents

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occurs.

reduction

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adjusted

and

Resistors

meter

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signal

The

in

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when

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C51

When

biased

The

with

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rectifier

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with

positive

in

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to

meter

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amplifier

output

meter is

the

R69

actual

the

the

for

circuit

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rise

and R59.

meter

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network

potential
needle

amount

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Components

ballistics.

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compensate

to

loading.

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output

meter's

circuit is

the

to

fall of

and

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R61

control

GR

difference

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of

limiting.

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signal

level,

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If

driven

are

directly

selected

level is

peak

and

5D

IC

designed to

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to gain

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voltage,

across

meter

downscale

R67,

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current

and

meter

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to

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indicate

to

+4

dBm

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characteristic

amplifier

characteristic.

meter is

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read zero

to

buffered

meter

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(left

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R68,

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line

amplifier

sense

reading

average

the

output

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0

(1.23

stage

V)

IC 5C

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resistor

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reading

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or

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The

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by

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POWER

The

voltage

regulators,

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The

of the

power

SUPPLY

power

filter

pilot

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bipolar

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capacitors

connected

is

indicated

to

VR2,

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provide

to

power

to the

power

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two

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ON

integrated

stability

negative

and

circuit

±18 volt

and

sides

DC.

-

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19

3

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.

5.1

GENERAL

Model

The

structed

should

parts

with

provide

used

are

workmanship

5.2

in

UREI

products

SPECIAL

NO

REPAIRS

This

against

initial

time

Card

from

of
to the

whom

factory

product is

defects

purchase.

purchase

the

repair.

Authorization

service,

Number

sturdy

a

styrofoam

space.

controls,

describing

one-way

pay

ship

visible

carton,

pellets,

Particular

switches,

the

1178

only

years

is

the

of

conservatively

meets the

PREVENTIVE

WARRANTY

AND

factory

material

in

This

returning

by

factory.

unit

was

Please

Number

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on

which

unit

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with

or

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shipping

SECTION

V

MAINTENANCE

an all

highest

trouble

solid-state

quality

free

rated

rigid

standards

MAINTENANCE

warranted

workmanship

and

limited

Should

purchased

call or

must

prepaid

shipping

warranty

registry

the

malfunction

a

will

write

accompany

directly

label.

shock-absorbing

"bubble-pack"

should

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and

costs

note

instructions

on any

unit,

components.

with

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for

have

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for

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to

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sure

Be

material

completely

paid to

be

to the

in-warranty

ruggedly

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normal

care.

application,

learned

REQUIRED.

original

year

one

activated

be

the

of

occur,

handle

factory

repairs.

for a

factory

it is

such

well

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filling

protecting

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top

return.

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con-

such,

it

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and

expect

to

purchaser

after

at the

Warranty

dealer

the

return

Return

prompt

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with the

packed in

foam

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rubber,

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the

unit

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INTERNAL

.

5

any

These

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carefully,

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of

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not

repairs

your unit

factory

the

special

problem in

SERVICE

controls

test

the

adjustments

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invalidate

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is

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test

the

ADJUSTMENTS

have

been

except

procedure

selected

during

out of

repairs.

the
the

warranty,

equipment,

set

service

efficient

at

most

after

that

performed

-

-

20

components

warranty

warranty.

we

experienced

Our

will

the

follows

in

be

factory

work.

should

the

this

in

period,

recommend

able

way.

and

If

exact

product,

attempts

and

that

personnel,

to

find

should

and

not

recalibration

peformed

be

manner

and

field

you

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order

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Before

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approximately

WARNING:

points

when you

5.3.1

positive

The

correct

checked

venient

+18 V

function

first,

check

(±0.6 V),

adjustments

5.3.2

This

justment.

that

you

this

to

MAKE

procedure.

(1 kHz,

trol

0

full

dBm on an

P.C.

dBm

should

not

board

(±0.5

be

bend

to

attempting

The

inside

work on

POWER

SUPPLY

and

of the

before

points

and

provided

Q-BIAS

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It is

control

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This

dBm) with

and

CW

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external

observe

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dB).

If it

performed.

pins

the

calibrations,

any

15 minutes.

full AC

the

the

line

chassis.

limiter

negative

entire

attempting

are the

Q2

(Q5)

in the

ADJUSTMENT

factory

important

correctly

adjustment

most

the

easily

limiting

Input

the

voltmeter.

meter

the

does

not so

Reinsert

voltages

unit.

metal

for

power

set

set,

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voltage

Be

with

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careful

the

are

Therefore,

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any

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V

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supply.

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correct

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and

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Remove Q7

indication.

indicate,

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avoids

subsequent

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covers

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important

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(collectors)

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There

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operation

therefore

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before

applying

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up

Turn

until

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from the

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socket,

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drifting.

several

at

personal

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of

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are

shock

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be

Con-

no

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limiter

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the

output

socket

input

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rise

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on

to

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control

voltmter.

output

drops

full

control

Mode

kHz

1

CW

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3 dB

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Attack

Release

Switch

Q-Bias*

with

set

0

until

turn the

to

settings

Input

Ratio

Meter

=

=
=
=
=
=

=
=

internal

signal

dBm

output

the

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dBm.

for

full

full
full

full
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+4

,

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full

to

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21

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CW

CCW

CW

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trimpots

the

reads

adjust

-

adjustments

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R13

input

+1 dBm on an

R13

to

and

and turn

(R113)

are:

OFF position)

R113)

Input

the

external

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the

5.3.3

METER ZERO

GR

AND TRACKING

Depress

Attack

the

meters to

the

Channel

B.

limiting

control so

-5

and

ing

adjust

and

reading

(R161)

mode

when

5.3.4

to

The

rejection.

Compression

Apply

Level

5.4

control

external

feed a

and

terminal of

GND

the

level,

meter

to

and

to

obtain

the GR

control

read 0

Apply a 1

described

as

that

with 5

VU

the GR

the unit is

give

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trimpot

Meter

signal

a

to

voltmeter.

AC

signal

adjust

reading

a

sensitive

more

meter

full

VU

kHz,

in the

the meter,

dB of

Tracking

VU reading

a 0

MODE

(RlOl)

R1

the

Set

Input

Output

Attack

Release

Ratio

Mode

to the input

achieve

the

of

the

for a

R1

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pushbutton.

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with trimpot

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0

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limiting.

control

in limiting,

when no

REJECTION

is used

controls as

number

to

full
full

full

CW

CCW

CW

20:1

GR

(100

+10 dB

Connect

same

limiter

output

the

input

input.

minimum

required.

ranges

2.5 mV (60

as

Disable

detented

for

R61

signal and

paragraph.

+4,

Switch the

R65

(R165)

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limiting

to adjust

follows:

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level,

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level to

Measure the

reading,

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position.

OFF

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meter back

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Meter

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for 5

Output

the

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to

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Input

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an

and

signal

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to

DIFFICULTY

CASE

IN

5.4.1

The

troubleshooting

problem.

working

is

it

inside the

best

described

OF

GENERAL

overall

Safety

send the

to

under

schematic,

table

considerations

paragraph

(Table

device.

unit

circuit

5-1)

If a

to

5-2.

-

description

can

outlined

problem

factory

the

-

22

often

in

cannot

(Section

used

be

Section II

easily

using

the

IV),

isolate

to

apply

solved,

be

procedure

and

a

when

5.4.2

PRECAUTIONS

TROUBLESHOOTING

FOR

cautious

Be

they

have

vulnerable

incorrect

sure

Be

probe

a

If

point,

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AC

it

remove any

outlet.

when testing

almost

to

unlimited

damage

voltages.

to

not

should slip,

will

very

components

life

when

accidentally

short any

for

likely

damage

while the

and

IC

when

terminals

example,

IC's,

transistor

used

properly,

shorted

when making

short

and

transistors

line

cord is

circuits. Although

they

connected to

or

are very

measurements.

out a bias

or

or supply

diodes. Do

connected to the

-

-

23

.

5.4.3 VISUAL

Look at

transistors

resistors

for

ciated

PROBLEM

Signal

through

circuitry.

does

the

wiring

and

which

pass

not

device.

IC's

TEST

and

are

may

TABLE

connections.

properly

look

burned,

5-1

.

POSSIBLE

Power

1,

Device

2.

Loose

3.

between

front

fitted

TROUBLESHOOTING

CAUSE

supply

in

or

PC

panel

Check

into

indicating

defective.

limiting.

full

broken

board

wires

controls.

and

be sure

to

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trouble in

that

sockets.

REMEDY

Check

Remove

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of

Isolate

supply

Q7

"full

all

Check

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voltages.

signal

If

.

problem

to

go

limiting".

resolder.

and

limiting.

No

Always

in

full

limiting

Incorrect

4.

amplifier

Bad

5.

Limiting

1.

Input

2.

threshold.

"Q”

3.

amplifier

GR

4.

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5.

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Contaminated

2.

level

Bias

Bias

hookup.

switched

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defective.

GR bus.

misad

PC

section.

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below

justed.

justed.

board.

Section

See

Installation.

Repair.

Attack

Turn

Increase

level

Adjust

Repair.

Check

Adjust

Clean

input

5.3.2).

(11

wiring.

5.3.2).

(11

5.5).

(11

II,

control

signal

CW.

-

-

24

.

PROBLEM

through

Hum

Distortion

limiting

output.

(during

mode).

TABLE

no

5-1.

TROUBLESHOOTING

POSSIBLE

Ground

1.

Failure

2.

output

CAUSE

Loop,

to

transformer

unbalanced

Mounted

3.

strong

Power

4.

Power

1.

Input

2.

Defective

3.

too

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supply.

supply

level

(Continued)

etc.

unbalance

load

close

field.

voltage.

high.

too

output

amp.

into

to

REMEDY

Section

See

Installation.

Ground

"COM"

chassis.

Relocate

Check

Repair

unit.

filter

needed.

as

Adjust.

Repair.

11,

to

caps.

Distortion

meter

VU

+8 range.

+4,

Excess

noise.

(during

reads

limiting).

low on

"Cracking"

1.

attack.

Low

2.

Bad

1.

Switch

2.

Problem

sound

frequency

meter.

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ICl,

in

on

distortion.

mode.

PEAK

4.

3,

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Attack

check

Select

Attack

of

Release

Replace.

1.

Switch

2.

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too

set

Q-Bias

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and/or

controls.

to

fast

5.3.2).

(^

settings

mode.

AVG

or

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25

.

BOARD

5.5

PC

Due

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Moisture,

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Existence

Supply

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Input

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meter

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(within

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Disconnect

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to

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to

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seconds

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Use

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test

circuits,

the

air

the

in

the

verified

be

with

read

to

the

on

limiter

the

surface

output

will

If

for

from

parts

return

contamination

longer

a

the

of

similar

(or

circuit

bottom

of

applying

to

before

it

limiter

result

may

operation

with

limiting

no

VU on

0

and

circuit

leakage,

level.

very

time

mains.

AC

distilled

stiff

board.

board

the

power

replace

replacing

happen

may

perform

to

of

a

indicated

the

locate

board

If no

rapidly

is

and

water

Brush

to

the

top

that

poorly.

slightly

in

to

due

Q7

Q7

test.

.

.

the

adjust

,

Remove

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simple

meter

around

and

contamination

0

to

on the

PC

cleaning

Prepare

isopropyl

and

bristle

brush)

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allow

and

limiter

the

socket

and

which

bottom

con-

leakage.

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VU

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of the

clean-

a

to

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. In

holds

is

5.6

CLEANING

The

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clean

cloth.

afforded

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as

may

wax

circuit

THE

front
such

panel

as

Additional

through

Never

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boards

if

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of

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light

a

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it

1178 may

the

409"

or

protection

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panel

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cleaned

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the

of

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meter

or

,

chassis.

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and

with

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preparation

wax

cleanser

the

contaminate

can

non-abrasive

soft

with

a

can

be

or

such

-

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26

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