Creative Engineering ROCK-A-FIRE EXPLOSION - Page 246

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Speakers

Check

the

fuses

for

the

speakers

and

impedance

on

the

speakers.

If

you

find

it

necessary

to

replace

any

blown

fuses,

be

sure

the

replacements

are

2 amp

fast

blow

fuses,

or

3 amp

at

the

greatest.

Warning

-

Placing

an

over

-

rated

fuse

will

possibly

cause

a

fire.

DBX

Box

Equipment

Required

Oscilloscope

Frequency

generator

Millivolt

meter

1.

Remove

the

box

from

the

audio

rack

and

open

it

up.

With

the

power

plugged

in,

check

the

Power

Supply

board

for

+5v,

-5v,

+12v,

-12v,

outputs,

see

pages

5-019

thru

5-025.

Check

variable

outputs

of

the

Power

supply

for

-12v

to

+12v

swing.

Repair

or

replace

if

necessary.

2.

Audio

adjust

-(not

needed

for

data

trouble-shooting)

Connect

the

signal

generator

to

track

1

NML

in,

and

apply

-lODBV

at

1khz,

see

pages

5-019

thru

5-025.

Connect

an

A.C.

Millivolt

meter

to

track

1

output.

Adjust

potentiometer

on

the

power

supply

board

and

track

1

of

the

DBX

card

for

-10DBV

output.

Repeat

the

procedure

for

track

2.

Note:

There

is

interaction

between

tracks

1

and

2

via

the

power

supply

potent1ometer.

So,

repeat

this

step

several

times

to

be

sure

that

it

is

balanced

between

the

two.

If

you

are

unable

to

do

this,

replace

the

DBX

boards

in

question.

One

board

may

load

the

other,

so

unplug

them

or

exchange

cables

to

verify

it

exactly.

3.

Data

adjust

-

Connect

the

signal

generator

to

track

3

NML

in,

and

apply

a -10DBV

at

2.25khz,

see

pages

5-019

thru

5-024.

Connect

a

millivolt

meter

and

O'scope

to

track

3

output.

On

the

millivolt

meter

obtain

a

reading

of

+7DBV.

Adjust

the

potentiometer

on

the

DBX

Tape

Select

Board

track

3

to

a

1/2

bit,

or

a

50%

duty

cycle

on

the

O'scope

display.

Repeat

this

step

for

track

4

normal

input.

The

inability

to

find

these

readings

identifies

the

board

as

a

failure,

therefore

replace

it

with

a

new

one.

4.

If

steps·

1-3

prove

unsuccessful,

check

the

wiring

and

connectors.

Phono

jacks

may

loosen,

Molex

pins

become

unseated,

and

wires

get

broken.

Repair

or

replace

if

necessary.

5.

Once

you

have

verified

that

the

outputs

from

the

DBX

are

good,

check

your

cables

and

connectors

back

to

the

controller.

Unplug

the

data

cable

and

see

if

it

has

a

data

output

at

the

controller.

If

not,

then

replace

it.

Continue

to

trace

the

signal

through

the

wiring,

back

across

the

Tunnel

and

into

the

Playback

Board.

It

is

unlikely

that

both

Playback

Boards

will

go

bad

at

the

same

time,

so

exchange

the

boards

to

verify

their

quality.

If

one

is

thought

to

be

bad,

try

adjusting

the

3/4

bit.

See

page

5-006.