Service manual

ManualsBrandsZenith ManualsComputer equipmentSM-Z-90

5-

2

11...--

DOUBLE-DENSITY

DISK

CONTROLLER

VCO BIAS ADJUSTMENT

Warm

up

the

Computer

for a

minimum

of 15

minutes

with

the

lid

closed.

Connect your

DVM

to test

point

1

on

the

H-/Z-89-37 board;

connect

the

negative

lead

to

ground

and

the

positive

lead to test

point

1.

The

reading

should

be

1.38 to 1.42 V (this is

the

VCO

bias voltage).

If

you

do

not

obtain

the

proper

voltage,

adjust

control RI0.

Disconnect

the

DVM.

VCO CENTER FREQUENCY

ADJUSTMENT

(WITH FREQUENCY COUNTER)

This

is

the

preferred

method

of

adjusting

the

VCO's center frequency.

Connect

the

frequency

counter

to test

point

2

on

the

board. Set

the

counter

to

the

100

ms

time

base.

The

counter

should

read

from 1975

to

2025 kHz.

If

it

does not,

adjust

control

R17.

Disconnect

the

counter.

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