Creative Engineering ROCK-A-FIRE EXPLOSION - Page 249

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while

you

are

doing

it.

You

can

take

the

board

off

of

the

support

stands

inside

the

drawer

wi.th

the

small

bolts

in

the

upper

corners.

Plug

in

the

exchanged

board

and

once

again

run

the

show

to

see

if

that

has

corrected

your

problem.

If

the

problem

moves

with

the

board,

then

replace

the

Long

Driver

Board,

see

page

5-026.

Playback

Board

Begin

by

exchanging

the

Playback

Board

with

the

one

in

the

other

drawer.

Run

the

show

again

and

if

this

solves

the

problem,

then

adjust

the

3/4

bit.

If

that

still

does

not

help

then

move

on

to

the

next

point

on

tracing

wiring

problems

on

the

Playback

Board.

Using

the

chart

for

the

Playback

Board

pins

outs,

see

pages

5-029

thru

5-032.

Check

continuity

on

these

wires

from

the

pins

on

the

board

to

the

Tunnel,

as

well

as

the

24

pin

plug

in

connector.

(Don't

forget

that

sometimes

a

simple

cleaning

of

the

connector

contacts

may

be

the

solution).

Adjusting

3/4

bit

Connect

channel

1

of

your

O'scope

to

pin

#7

of

U19

for

voltage

adjustment.

Adjust

the

10k

potentiometer

to

2

volts.

Connect

channel

2

of

your

O'scope

to

test

point

4

(tp4)

and

adjust

the

50k

potentiometer

to

3/4

bit

or

75%

of

the

wave.

Note:

these

two

adjustments

are

interactive

so

try

moving

the

'pots'

a

couple

of

times

to

see

how

they

affect

each

other

before

trying

to

set

it

exactly.

Watch

the

LED

to

see

if

the

light

goes

out

when

the

tape

is

running.

If

you

are

unable

to

adjust

the

3/4

bit

return

the

board

for

replacement.

Wire

harness

and

cable

trouble-shooting

In

order

to

find

if

a

cable

or

wire

harness

is

good,

it

is

easier

to

test

it

with

the

power

on.

In

some

instances,

like

in

actually

trouble-shooting

the

Playback

Board

or

Tunnel,

it

may

be

easier

to

take

them

out

of

the

circuit

and

read

the

connections

by

continuity

checking.

Long

Driver

Board

Harness

Find

the

contact

on

the

24

pin

connector

on

the

output

to

the

character

and

it's

corresponding

pin

near

the

leg

of

the

transistor,

and

check

for

continuity,

see

pages

5-037

thru

5-064.

If

you

do

not

have

continuity,

repair

the

connection

and

retest

it

by

jurnpering

the

bit.

Tunnel

Wiring

-

Check

the

Tunnel

and

see

if

the

connector

in

question

has

25v.

corning

out

of

the

Tunnel.

Unplug

the

cable

from

the

Tunnel

that

the

movement

occurs

in,

and

read

the

voltages

on

the

pins

between

#23 - #24

and

ground.

If

you

have

the

25

volts

on

these

pins,

then

you

must

trace

the

wiring

backward

through

the

cable

to

the

solenoid.

If

the

break

is

there,

then

repair

or

replace

the

cable

with

a new

one.

See

pages

5-027

and

5-028,

also

5-031

thru

5-034,

and

5-037

thru

5-046.

Valve

Bank

Wiring - In

order

to

check

the

wiring

of

the

valve

bank

harness

it

is

necessary

to

unplug

the

24

pin

connector

at

the

valve

bank

and

check

for

continuity

between

pins

23/24

and

the

5-Q06