Ann arbor Ambassador User manual

ANNAR R

-

co

(.)

•

c::::

J:

(.)

AMBASSADOR

TECHNICAL

MANUAL

TABLE

OF

CONTENTS

CASE

................................ 1-1

MONITOR

BOARD

Theory

of

Operation

•••••••••••••••

2-1

Setup

Procedure

•••••••••••••••••••

2-6

Troubleshooting

Guide

•••••••••••••

2-9

Replacement

Parts

•••••••••••••••••

2-13

LOGIC

BOARD

Theory

of

Operation

Replacement

Parts

KEYBOARD

ACCESSORIES

Compu

ter

Cable

Printer

Cable

DRAWINGS

201185 Monitor Board

201197

Terminal

Board

201199

I/O

Board

205305 E-Case

210000 D-Case

3-1

3-13

4-1

5-1

5-2

12/16/81

CASE

01/28/81

PAGE

1-1

The

terminal

is

supplied

in

two

different

case

configurations:

E-Case

(see

drawings

205305) and D-Case

(see

drawings

210000).

differ

only

in

size

and

esthetics.

The

electronics

within

them

and

Logic

board)

are

identical.

INSTALLATION

ACCESS

the

Ann

Arbor

The

two

cases

(Monitor

board

In

both

cases,

access

for

installation

is

via

an

access

door

at

the

rear

of

the

case.

All

connections

to

the

terminal

are

made

behind

this

door

(see

User

Guide,

Checkout

and

Installation).

No

connectors

protrude

from

the

back

to

be

knocked

loose,

damaged,

or

occupy

extra

space.

The

door

safely

clamps

the

ca-

bles

as

they

issue

from

the

case.

Any

excess

cable

lengths

may

be

stored

within

the

case

for

a

neater

installation.

MAINTENANCE

ACCESS

Access

for

installation

is

perfectly

safe

to

un-trained

personnel.

Neither

the

CRT

nor

hazardous

portions

of

the

circuitry

are

accessible

through

the

ac-

cess

door.

Access

for

maintenance

is

NOT

SAFE

for

untrained

personnel.

The

CRT

is

made

of

glass·

and

will

implode

if

broken.

The

Monitor

board

generates

voltages

up

.to 17KV and

portions

of

its

circuitry

operate

with

a

"hot"

ground.

ACCESS

FOR

MAINTENANCE

SHOULD

BE

ATTEMPTED

ONLY

BY

QUALIFIED

TECHNICAL

PERSON-

NEL.

In

the

E-Case,

access

for

maintenance

is

by

removal

of

the

rear

hood.

Place

the

unit

with

its

screen

down.

Remove

the

access

door,

and

unplug

the

P1-

connector

(horizontal

white

connector

below

the

keyboard

connector).

Remove

the

two

screws

at

the

side

of

the

hood

(that

attach

it

to

the

bezel)

and

lift

it

free.

Steer

the

P1-connector

so

that

it

doesn't

catch

on

the

Logic

board.

This

exposes

the·

Monitor

board

for

debug.

To

expose

the

Logic

board,

remove

the

four

screws

attaching

it

to

the

hood and

lay

it

in

the

bottom

of

the

hood

(or

other

insulated

surface),

and

re-connect

P1.

In

the

D-Case,

access

for

maintenance

is

by

removal

of

the

top

cover.

Remove

the

four

screws

from

the

base

and

lift

off

the

cover.

This

exposes

both

the

Monitor

and

Logic

boards

for

debug.

CASE

01/28/81

PAGE

1-2

-

BOARD

REPLACEMENT

To

replace

the

Logic

board,

unplug

the

P1connector

(and

the

keyboard

and

1/0

cables

if

plugged

in),

and remove

the

four

screws

attaching.

it

to

·the

hood

.(E-Ca~e)

or

frame

(D-case).

To

replace

the

Monitor

board:

1.

Unplug

the

CRT

socket.

2.

Detach

the

anode

cap.

Use a

grounded

screwdriver

under

the

rubber

cap,

shorting

out

the

pins

(to

discharge

any

residual

high

voltage

that

might

be

present).

Squeeze

the

pins

together

slightly

to

release

the

cap

from

the

tube.

3.

Unplug

the

yoke

connectors,

REDIBLK

near

the

front

of

the

board,

YEL/GRN

near

the

back

of

the

board.

4.

Detach

the

GND

spring

at

the

top

and

bottoIL.Of

the

tube.

5.

Remove

the

four

screws

attaching

the

board

to

the

frame.

6. Unplug

the

in-line

Power and

Contrast

pot.connectors.

Reverse

the

procedure

to

install

the

new

board.

After

installing

a

new

Moni-

tor

board,

the

setup

procedure

(given

in

the

Monitor

section)

should

be

fol-

lowed.

MONITOR

-

THEORY

OF

OPERATION

05/11/81

PAGE

2-1

THEORY

OF

OPERATION

The

Monitor

board

contains

the

monitor

electronics,

and

the

power

supply

for

both

the

Monitor

and

the

Logic

boards.

The

Monitor

100

200

300

1.i00

500

600

board

consists

of

six

sections:

Power

Supply

Vertical

Deflection

circuit

Video

Drive

circuit

Horizontal

Deflection

circuit

CRT

Bias

network

Bell

circuit

The

Monitor

board

drawings

(see

drawings

201185)

consist

of

three

sheets.

Sheet

III

is

an

Assembly

drawing

of

the

board

showing

component

locations.

Component

designations

carry

their

section

number.

Sheet

112

is

a

Schematic

drawing

of

the

100

and

600

sections

of

the

board.

Sheet

113

is

a

Schematic

drawing

of

the

200

through

500

sections

of

the

board.

The

sections

are

described

below

in

reference

to

their

Schematic

drawings.

100

POWER

SUPPLY

A

switch-mode

power

supply

is

used

to

provide

good

efficiency

over

a

wide

range

of

incoming

line

voltages.

Elimination

of

the

line

transformer

elim-

_

inates

display

"swim" when

used

on

off-frequency

lines.

By

synchronizing

the

switching

with

the

horizontal

sweep

rate,

any

switching

noise

that

might

be

coupled

into

the

display

is

masked

in

the

horizontal

blank

period.

INPUT

CIRCUIT. The

incoming

line

voltage

is

full-wave

rectified

by a

diode

bridge

Dl00

and

stored

(at

about

160VDC)

in

capacitor

Cl08.

Fl00

and

S100

fuse

and

switch

the

AC

line.

Capacitors

C100,

Cl03,

Clll,

Cll2

provide

filtering

of

the

line.

Thermistor

RT100

limits

the

surge

current

during

a

cold

start.

C104,

Cl05, Cl06,

Cl07

reduce

diode

switching

transients.

R10l

is

a

bleeder

to

discharge

Cl08

following

power

off.

SWITCHING

CIRCUIT. The

voltage

on

cl08

is

impressed

across

a

switching

transformer

Tl00

and

a

switching

transistor

Ql05.

When

Q105

is

on,

T100

charges

from

Cl08.

When

Q105

is

turned

off,

the

collapsing

magnetic

field

dumps

the

energy

stored

in

Tl00

into

the

secondary

windings.

The

induced

vol-

tages

are

rectified

and

filtered

to

provide

the

required

DC

supplies.

D112,

R1l6,

C135

form

a

snubber

network

that

protects

Ql05

during

turn-off.

SWITCHING

REGULATOR

CIRCUIT.

One

of

the

secondary

windings

(pins

5,

6)

is

rectified

and

filtered

(through

Dl04,

Rll0,

C130)

to

form

a

control

voltage.

This

voltage

feeds

a

switching

regulator

circuit,

consisting

of

IC100

and

Q101-104.

This

circuit

operates

at

the

horizontal

sweep

rate

of

the

monitor,

and

controls

the

on-time

of

Ql05

so

as

to

maintain

the

voltage

constant

with

varying

line

and

load.

The

control

voltage

at

C130

is

divided

through

Rll2,

RV100, R127

to

about

2

volts

and

fed

into

the

comparator

input

(pin

4)

of

IC100.

C141, R133

provide

MONITOR.-

THEORY

OF

OPERATION

05/11/81

PAGE

2-2

ACfeed-forward

compensation

across

the

divider

for

improved

ripple

rejection.

Within IC100,

the

control

voltage

is

compared

against

a

2-volt

internal

refer-

ence,

and an

error

voltage

generated

at

5.

The

-error

voltage

is

divided

and

filtered

by

R132, R131,

C128

and

applied

to

the

base

of

Ql02. R132,

R131

set

the

maximum

on-time

of

Q5

to

about

60%

of

the

horizontal

sweep

time.

Q102

buffers

the

error

signal

through

R135

into

.

the

pulse-width

modulator

input

(pin

8)

of

IC100.

R136

sets

the

minimum

on-

time

of

Ql05

to

about

15%

of

the

horizontal

sweep.

Th~

output

of

IC100

(pin

1)

is

a

square

.wave

having a frequency determined

by

the

input

at

7 and a

duty

cycle

determined

by

the

input

at

8.

At

7,

R122,

C138

set

a

free-running

oscillator

frequency

slightly

lower

then

the

horizontal

sweep

rate.

The

oscillator

is

then

locked

to

the

horizontal

sweep

by

an

input

from

the

flyback

transformer

T401

coupled through

C139

to

the

base

of

Ql01.

Ql03, Ql04

amplify

the

square

wave

and

provide

push-pull

drive

to

the

base

of

Ql05.

At

normal

line,

Ql05

should

be

on

about

1/3

of

the

horizontal

sweep

time.

When

the

line

drops

or

the

load

increases,

the

on-time

increases.

When

the

line

rises

or

the

load

decreases,

the

on-time

decreases.

START-UP

CIRCUIT.

The

regulator

circuits

are

powered

(through

R143, Dl11,

C127, C126) from

the

same

winding

as

the

control

voltage

is

derived.

At

ini-

tial

turn":on,

this

supply

is

not

active.

A

start-up

circuit

(Ql08-110)

pro-

vides

power

to

the

regulator

circuits

during

this

period.

At

turn':"on,

the

voltage

across

Cl08

is

impressed

across

Rl03 and

zener

Dll3,

providing

a

24-volt

reference

to

the

start-up

circuit.

Cl09

charges

through

Rl02.

When

the

voltage

across

ClOg

builds

sufficiently,

Ql08

turns

on,

turn-

ingon

Ql09 and Ql10.

ClOg

discharges

through Qll0

into

the

30-volt

supply,

powering

the

regulator.

When

the

voltage

across

ClOg

drops

sufficiently,

Q108

turns

off,

turning

off

Q109

and Ql10, and

the

process

repeats,

if

reqUired,

as

the

voltage

across

the

control

winding

builds.

CURRENT

LIMITING.

A

current-limit

circuit

(Ql07, Ql06, Ql11, Ql00)

protects

the

switching

circuit

during

turn-on,

or

shorts

on

any

of

the

secondary

vol-

tage

supplies.

The

average

current

through

the

switching

circuit

is

monitored

by

Rl17,

C136

in

the

emitter

of

Ql05. This

signal

is

filtered

and

divided

through R130, .

C145, R138,

R140

to

the

base

of

Ql07. Ql07

is

normally

off,

and Ql00

holds

the

enable

input

of

IC100

low

(about

1.2V).

If

the

average

current

becomes

excessive,

Ql01

turns

on.

This

turns

on Ql1l

which

discharges

C143, and

(through

Ql00)

pulls

the

enable

input

of

IC100

high

(above 2V). This

disables

the

comparator,

causing

the

on-time

of

Ql05

to

pull

back

to

its

minimum

setting.

The

secondary

voltages

drop

back,

the

over-

current

signal

drops

back,

and

Ql07and

Qll1

turn

off.

Because

C143

is

discharged,

Ql00

cannot

immediately

re-enable

the

comparator.

Rather,

as

C143

charges,

the

voltage

at

3

slowly

drops,

the

on-time

of

Ql05

slowly

increases,

and

the

secondary

voltages

come

up

gradually_

MONITOR

-

THEORY

OF

OPERATION

05/11/81

PAGE

2-3

If

the

short

persists,

Q107

will

again

turn

on,

and

the

regulator

will

pull

back

and

try

again.

However,

during

each

Q111

on-period,

C146

is

being

charged

through

D101

and R158.

If

the

short

persists

through

several

trys

(ie,

it

is

a

"hard"

fault),

the

voltage

across

C146

will

become

large

enough

to

turn

Q106

on.

This

latches

the

supply

into

a

pulled-back

state,

and

can

be

relieved

only

by

powering

down

and

correcting

the

fault.

200

VERTICAL

DEFLECTION

CIRCUIT

The

vertical

deflection

circuit

is

shown

at

the

top

of

sheet

3.

It

accepts

vertical

sync

pulses

from

the

logic

board

and

controls

the

Y-axis

of

the

CRT.

IC200

is

the

vertical

oscillator.

R204, R202, C202

set

a

free-running

oscil-

lator

frequency

slightly

lower

than

the

vertical

sweep

rate.

The

oscillator

is

then

locked

to

the

vertical

sweep by

the

sync

pulses

from

the

logic

board.

The

oscillator

output

(pin

6)

is

a

sawtooth

waveform

developed

across

C202.

C202

is

charged

(through

R202, R204)

while

the

sync

pulse

input

(pin

5)

is

high,

and

discharges

(through

R204) when

the

input

goes

low.

Zener

D200

in

the

12V

supply

stabilizes

the

waveform

against

power

supply

variations.

Q207

is

a Dar

ling

ton

amplifier/buffer.

not

to

load

down

the

charging

of

C202,

the

sawtooth

waveform

to

Q200.

RV200

vertical

height

adjustment.

It

has

a

high

input

impedance

so

as

and

provides

a low

impedance

source

of

in

the

emitter

of

Q207

provides

for

Q200 and

Q201

form

a

differential

amplifier

that

compares

the

generated

sawtooth

with

a

signal

the

current

actually

flowing

through

the

yoke

(R224)

and

the

voltage

across

it

(R214).

The

signal

is

modified

by

low-

pass

filter

R210, RV202, and C208

to

provide

for

linearity

adjustment

of

the

vertical

sweep.

Q202

buffers

the

output

of

the

differential

amplifier

and

drives

the

output

transistors

Q203 and Q204. The

transistors

are

biased

by

the

network

R213,

D201, R219, R217, R218,

and

the

emitter

resistors

R216, R220.

During

trace

time,

the

transistors

drive

the

yoke

with

a

positive-going

ramp

from

about

-2V

to

+2V.

C213

is

charged

to

about

24V

through

R221

and D202.

The

retrace

generator

Q205

is

biased

off

by R222, R223, C214.

When

vertica

1

retrace

occurs,

Q205

is

turned

on (

through

C214, R223) •

This

pulls

the

plus

side

of

C213

to

-12V,

which

pulls

the

yoke

(through

Q204)

to

about

-36V,

resulting

in

a

fast

(about

400

microsecond)

vertical

retrace.

MONITOR

-

THEORY

OF

OPERATION

300

VIDEO

AMPLIFIER

500

CRT

BIAS

NETWORK

05/11/81

PAGE

2-4

The

video

amplifier

is

shown

at

the

lower-left

of

sheet

3.

It

accepts

video

and

blanking

signals

from

the

logic

board

and,

in

conjunction

with

the

CRT

bias

network,

controls

the

Z-axis

of

the

CRT.

Q300,

Q301

form a

non-inverting

video

amplifier

with

a

gain

of

1

to

1.5.

TTL-

level

video

from

the

logic

board

is

ac-coupled

into

the

amplifier

through

C313.

C302

adds

a

little

leading-edge

peaking

to

the

video

for

better

charac-

terdefinition.

RV300

sets

the

amp.lifier

gain

(and

is

the

,external

'bright-

ness'

contro

1)

•

Q303

sets

the

black-level

of

the

video

at

the

input

to

the

amplifier.

It

is

turned

on

during

horizontal

retrace,

by a

pulse

coupled

from

the

flyback

transformer

T401

(pin

8),

and

gates

in

a

voltage,

set

by

the

black-level

ad-

justment

RV300,

to

control

the

charge

on C313,

holding

the

black-level

con-

stant

regardless

of

signal

input.

Q305,

Q304

form a

cascode

amplifier

that

drives

the

CRT.

L300

provides

addi-

tional

video

peaking.

D300

(in

series

with

the

70V

supply)

ensures

CRT

cutoff

at

power-down

to

avoid

phosphor

burn.

Q302

pulls

the

input

to

the

amplifier

to

GND

(video

off)

in

response

to

a

Video-blanking

signal

from

the

logic

board,

if

provided.

In

the

CRT,·

the

video

amplifier

drives

the

cathode.

Gl

(control

grid)

bias

is

set

by R502, RV500, R501.

G2

(accelerating

anode)

bias

is

set

by R503, R504.

400

HORIZONTAL

DEFLECTION

CIRCUIT.

The

horizontal

deflection

circuit

is

shown

at

the

lower

right

of

sheet

3.

It

accepts

horizontal

sync

pulses

from

the

logic

board

and

controls

the

X-axis

of

the

CRT.

IC400

is

the

horizontal

oscillator.

RV403, R414, C409

set

the

free-running

oscillator

frequency.

The

horizontal

flyback

pulse

is

shaped

into

a

sawtooth

and

coupled

to

4

of

IC400

through

the

network

R410, R413, C401, C402.

Horizontal

sync

is

differentiated

and

coupled

to

3 by R400, C400.

Pins

3

and 4

are

the

inputs

of

a

phase

comparator

which

produces

an

output

voltage

proportional

to

the

phase

difference

between

the

sync

and

sawtooth

inputs

at

5.

R412, C408

filter

the

voltage,

and

R411

couples

it

to

7

to

provide

dynamic

control

of

the

oscillator

frequency

and

phase.

The

oscillator

output

(pin

1)

is

a

square-wave

at

the

horizontal

frequency,

having

a

duty

cycle

determined

by R401, R402. The

output

is

buffered

by

Q400

and

transformer-

coupled

through

T400

to

the

base

of

Q401.

When

Q401

is

on,

the

flyback

transformer

T401

charges

from

the

70V

supply.

When

Q401

is

turned

off,

the

collapsing

magnetic

field

looks

into

a

parallel

resonant

circuit

consisting

of

C410

and

the

circuit

containing

the

horizontal

winding

of

the

yoke

(L405).

The

energy

stored

in

T401

is

dumped

rapidly

into

the

yoke.

circuit,

causing

the

beam

to

"flyback"

to

the

left

edge

of

the

MONITOR

-

THEORY

OF

OPERATION

05/11/81

PAGE

2-5

screen.

When

the

voltage

across

the

circuit

trys

to

ring

back

through

zero,

DItOO

con-

ducts

-and

the

yoke

circuit

gradually

discharges,

sweeping

the

beam

toward

the

center

of

the

screen.

When

the

beam

nears

the

center

of

the

screen,

Q104

takes

over,

actively

continuing

the

sweep and

re-charging

T401.

Some

of

the

energy

stored

in

TIt01

is

dumped

to

other

loads.

a)

Flyback

pulse

feedback

to

the

horizontal

oscillator

and

the

-70V

supply.

b)

Flyback

sync

pulse

to

the

switching

regulator

(winding

A,

B)

c)

Filament

power

for

the

CRT

(winding

7,

8)

d)

500V

supply

for

the

CRT

focus

and

G2-bias

circuits

(D401)

e)

17KV

anode

supply

for

the

CRT

(D403)

The

other

components

in

the

yoke

circuit

provide

correction

for

the

sweep.

LIt06

is

a

variable

inductor

that

provides

for

horizontal

width

adjustment.

L407

is

an

adjustable

saturable

reactor

that

compensates

for

non-linearities

at

the

end

of

the

sweep due

to

yoke

resistance.

CIt15

provides

"S"

correction

at

the

extreme

ends

of

the

scan.

The

G4

(focus)

grid

of

the

CRT

is

set

by

RV400

for

best

focus

at

the

center

of

the

screen.

A

dynamic

focus

circuit

(Q402)

permits

this

focus

to

be

main-

tained

over

the

full

sweep.

The

voltage

developed

across

CIt15

forms

a

parabo-

la

across

the

sweep.

An

adjustable

amount

of

this

voltage

may

be

picked

off

by

RV401, and

added

to

the

DC

level

set

by RV400.

MONITOR-

SETUP

PROCEDURE

05/11/81 Page

2-6

SETUP

PROCEDURE

EQUIPMENT

REQUIRED.

af

Line-isolated

variable

AC

sUpply

(Variac)

with

current

meter

b)

Voltmeter

c)

Oscilloscope

with

100X

probe

SETUP

PROCEDURE.

1.

Preset

all

controls

to

mechanical

center,

except:

a.

RV300

(contrast)

full

counter-clockwise

(minimum

contrast)

b.

RV301

(black-level)

fully

counter-clockwise

from

rear

(minimum

drive)

2.

Connect

monitor

to

isolated

supply

with

voltage

turned

down

to

zero.

3.

Turn

on

monitor

and

variac.

that

the

switching

supply

starts.

Adjust

the

voltage

up

slowly,

making

sure

Adjust

to

l20VAC

if

no

problems

occur.

4.

If

the

raster

comes

up

too

bright,

adjust

RV500

(brightness)

so

that

ras-

.

ter

is

just

on.

5.

Adjust

RV202

(vertical

linearity)

and

RV200

(vertical

height)

'for

approxi-

mately7"

height.

6.

Adjust

L406

(horizontal

width)

for

approximately

10"

width.

(Note:

On

high

,sweep

rate

units,

L406

may

be

shorted

out

by

a jumper

on

the

back

of

the

board,

for

maximum

width.

If

it

is

necessary

to

reduce

the

width,

remove

this

jumper.

7.

Adjust

RV100

(B+)

for

70VDC

at

junction

of

R105

and C117. Check

the

+12V,

-12V,

+5V,

-5V

supplies

for

proper

levels.

(The

latter

3

supplies

may

be

as

much

as

lV

high

as

there

is

no

logic

board

load.)

8.

Check

that

the

CRT

filament

voltage

(brown

leads

of

the

CRT

socket)

is

between

5.9

and

6.7VAC.

If

outside

of

this

range,

the

filament

dropping

resistor

(R428) should be changed

in

the

range

2.7

to

4.7

ohm,

1

watt.

9.

Turn

off

the

monitor.

Connect

the

logiC

board.

Turn

on

the

monitor.

10. Check

the

unit

for

proper

operation:

a.

Adjust

RV403

(horizontal

hold)

for

horizontal

pull-in,

if

needed.

b.

Check

that

raster

is

locked-in

vertically.

MONITOR

-

SETUP

PROCEDURE

05/11/81

Page

2-7

c.

Check

that

video

is

present.

(May

require

adjustment

of

brightness

and

contrast

controls.

Adjust

for

normal

level.)

d.

Re-adjust

height

(approx

7")

and

width

(approx

10

11

)

if

needed.

11.

Reset

the

70V

supply,

and

check

all

supplies

for

proper

levels.

Fill

the

screen

with

characters.

If

the

logic

board

provides

for

both

'bright'

and

'dim'

characters,

use

'bright'.

Reduce

the

line

voltage

slowly.

The

line

current

will

increase

(from

about

O.5A)

to

a

level

which

causes

the

over-

current

protection

circuit

to

attempt

to

shut

down

the

supply.

Check

that

this

'trip

point'

occurs

between

0.65A and 0.9A

line

current.

Reset

the

line

voltage

to

120VAC.

12.

Short

out

TP1

(horizontal

sync)

with

a

short

clip-lead.

Adjust

Rv403

for

horizontal

free-running

frequency.

Remove

clip-lead.

Horizontal

should

pull-

in

to

sync.

Video

should

be

phased

on

raster

so

that

there

is

no

fold-over.

13.

Connect

oscilloscope

to

TP2

(CRT

cathode).

Set

vertical

on

DC

at

20V

(p-p)

per

division.

Set

horizontal

sweep

at

horizontal

rate

(or

vertical

rate

if

logic

board

generates

only

vertical

blanking).

14.

Set

up

contrast,

brightness,

and

black-level.

a.

With

RV300

(contrast)

at

minimum,

adjust

RV301

(black-level)

so

that

the

black-level

of

the

video

signal

(see

diagram)

is

at

60VDC.

(Caution:

Do

not

mis-adjust

this

control,

as

over-dissipation

of

the

video

amplifier

Q304

may

result.)

70VDC

1 1

60VDC

1-------------------------------1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 I I 1 1 1 I 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1

Blanking

/

1-----

Black

level

1 1 1

White

level

b.

Turn

the

contrast

control

to

maximum. The

video

output

should

be

capa-

ble

of

40V

(p-p)

from

black

level

to

peak

white

without

compression.

c.

With

the

contrast

set

for

normal

level,

adjust

RV500

(brightness)

so

that

the

background

level

is

slightly

blacker

than

black.

If

the

unblanked

raster

is

not

black,

or

if

very

little

reserve

control

remains,

the

brightness

range

of

RV500

may

be

adjusted

by

changing

R501

in

the

range

56K

to

82K

ohm,

1/2

watt.

d.

Turn

the

contrast

control

to

IIll.mmum.

The

characters

must

still

be

visible

(but

should

be

dimmer

than

a

normal

setting).

If

the

character

brightness

is

too

high,

the

brightness

control

may

be

adjusted

slightly

to

bring

the

brightness

level

down.

(Caution:

Under no

circumstances

should

turning

the

contrast

control

to

minimum

result

in

a

completely

blank

display.

At

maximum

contrast,

this

will

cause

the

video

amplifier

to

compress

and

cause

streaking

of

the

displayed

video.

15.

Adjust

RV200

and

RV202

(vertical

height

and

linearity),

if

needed.

MONITOR-

SETUP

PROCEDURE

05/11/81

Page

2-8

16.

Adjust

L406 and L407

(horizontal

width

and

linearity),

if

needed~

17.

Check

the

display

geometry

of

the

CRT

and

yoke.

Re-centering

of

the

display

may

be

done

if

it

improves

the

geometry.

If

the

display

is

not

ac-

ceptable,

magnets

may

be

moved

or

changed,

but

they

should

always

be

glued

in

"place

in

the

liner

pockets

provided.

·18.

Re-adjust

the

vertical

height

and

linearity,

and

the

horizontal

width

and

linearity,

for

proper

aspect

ratio

(about

7"

H x 10" W).

(Note:

To

adjust

hor-

izontal

linearity,

turn

the

biasing

magnet

in

L407

until

the

left

side

of·

the

raster

just

stops

moving

toward

the

center

of

the

scre.en.At

the

same

time,

the

right

side

will

be

moving

toward

the

outside

edge

of

the

screen.

The

correct

effect

is

to

compress

the

left

side

and

stretch

the

right.)

19.

Adjust

the

dynamiC

focus

as

follows:

a.

Connect

oscilloscope

to

TP3.

Set

vertical

on

DC,

100V

per

division.

b.

Adjust

Ry401

(dynamic_focus) so

that

there

is

no dynamic

correction.

c.

Adjust

RV400

(focus)

for

best

focus

at

the

center

of

the

screen.

Note

the

DC

voltage

required.

d.

Adjust

RV400

for

best

focus

in

the

upper-left

corner

of

the

screen.

Again;

note

the

DC

voltage

required.

e.

Adjust

Rv401

so

that

the

amplitude

of

correction

(at

TP3;

see

diagram)

is

the

difference

between

the

voltage

readings

noted

above.

f.

Again,

adjust

RV400

for

best

center

focus.

The

upper-left

corner

should

"

now

be

in

focus.

Screen

left

edge

_

Screen

r:ight

edge

/ \

-\

-

/ / \ / \

/ \ / \

_Horizontal

retrace

20.

The

monitor

is

now

set

up

properly.

MONITOR

-

TROUBLESHOOTING

GUIDE

05/11/81

Page

2-9

TROUBLESHOOTING

The

following

is

intended

to

provide

troubleshooting

hints

in

the

various

sec-

tions

of

the

Monitor

board,

based on an

understanding

of

the

tions.

.It

is

not

intended

to

be an

exhaustive

troubleshooting

procedure.

100

POWER

SUPPLY

1.

No

raster;

no power

supply

voltages.

a.

Check

fuse.

If

open:

1) Check

Q105

for

short.

If

Q105

is

shorted,

check

also

R111.

2)

Check

D100

for

short.

3)

Check

C108

for

short.

b.

Check

voltage

at

D111.

If

the

power

supply

is

trying

to

start,

the

vol-

tage

will

rise

toward

30V,

fall

back

to

about

6V,

and

repeat.

If

it

is

not

trying

to

start

1>

Check

that

C108

charges

to

about

160VDC.

2)

Check

that

D113

provides

24V

reference.

·3)

Check

the

start-up

circuit

(Q108, Q109, Q110, C109).

c.

Disconnect

the

secondary

loads

from T100, one

at

a

time

starting

with

+10V,

to

see

whether

a heavy

load

or

short

in

the

secondary

is

causing

the

supply

to

current

limit

and

shut

down.

If

lifting

a

secondary

permits

the

supply

to

come

up,

troubleshoot

to

the

section

causing

the

overload.

d.

Check

Q105

for

low

resistance.

Also check

R117

for

high

resistance

(which

will

cause

the

current-limit

circuit

to

sense

an

overload).

e.

Check

the

switching

regulator

circuit

(IC100).

f.

Check

the

current-limit

circuit

(Q101, Q106, Q111, Q100).

g.

Check

for

oscillator

input

at

IC100

1 (Q101, C138).

h.

Check

for

faulty

Q102, Q103, Q104.

MONITOR

-

l'ROUBLESHOOTING

GUIDE

05/11/81 Page 2-10

200

VERTICAL

DEFLECTION

1.

No

vertical

deflection.

a.

Check

for

output

from

vertical.output

circuit

(Q203,.Q204).

If

no

out-

put,

check

for

signal

at

output

of

(Q202, Q200/201,

Q207,

IC200).

The

output

of

Q200/201

is

a

square

wave

at

the

vertical

rate.

All

others

are

of

sawtooth waveshape.

b.

Check yoke

circuit.

2.

Reduced

height.

a.

Check

vertical

height

adjustment

(RV200).

b.

Check

for

low

B+

voltage

(+12V).

c.

Check

for

low

gain

in

one

of

the

vertical

stages.

3.

Poor

linearity

(top

or

bottom compressed).

a.Checklinearity

adjustment

(RV202).

b.

Check

diff

amp

(Q200/201).

c.

Check

vertical

output

(Q203/204).

4.

Loss

of

vertical

sync.

a.

Check

for

sync

pulse

from Logic

board.

If

not

present,

troubleshoot

to

Logic

board.

b.

Check

vertical

oscillator

(IC200).

300

VIDEO

DRIVE

1.

No

video;

raster

OK.

a.

Check

for

video

signal

from Logic

board.

If

not

present,

troubleshoot

to

Logic

board.

b.

Check

for

signal

at

base

of

Q305.

If

not

present,

check

video

circuit

(Q300, Q301,

Q302,

Q303).

c.

Check

for

signal

at

TP2.

If

not

present,

check

video

drivers

(Q304,

Q305).

d• Replace

CRT.

2.

No

video;

raster

brightness

too

high.

a.

Check

for

short,

or

improper

bias,

in

video

drivers

(Q304, Q30S).

MONITOR

-

TROUBLESHOOTING

GUIDE

05/11/81

Page 2-11

3.

Weak

video;

raster

and

video

present,

but

poor

contrast.

a.

Adjust

brightness

(RV500),

contrast

(RV300), and

black-level

(RV301).

See

Setup

procedure.

b.

Check

video

amp

(Q300, Q301) and

contrast

control

circuit.

c.

Check

black-level

clamp

circuit

(Q303).

d.

Check

video

drivers

(Q304, Q305)

for

leakage

or

low

gain.

e.

Replace

CRT.

4.

Brightness

level

variations

a.

Check

CRT

video

and

grid

inputs

for

corresponding

variations

in

vol-

tage.

b.

Replace

CRT.

5.

No

raster;

power

supply

and

high

voltage

OK.

a.

Check

filament

voltage.

b.

Check

brightness

adjustment

(RV500) and

bias

of

G1.

c.

Check

bias

at

G2

and

G4.

d.

Replace

CRT.

400

HORIZONTAL

DEFLECTION

1.

No

raster;

no

high

voltage.

a.

Check

for

+10V.

If

not

present,

disconnect

3

of

T401

(flyback).

If

this

allows

+10V

to

come

up,

look

for

shorted

Q401

or

diode

in

the

collec-

tor

circuit

of

Q401.

b.

Check

for

output

from

the

horizontal

oscillator

(IC400

1).

If

not

present,

check

1

for

sawtooth

signal

(at

the

free-running

oscillator

frequency).

If

no

signal,

check

for

bad C409,

RV403.

Check

6

for

+8v.

If

not

present,

check

for

+12V

supply

or

shorted

C403.

If

all

OK,

replace

IC400.

c.

Check

for

input

to

base

of

Q401.

If

not

present,

check

Q400, T400.

d.

Check

for

pulse

at

collector

of

Q401.

If

not

present,

replace

Q401.

Note:

If

there

is

a

signal

at

the

collector,

but

not

the

proper

level

or

waveform, check

for

faulty

flyback,

yoke,

or

component

in

the

yoke

cir-

cuit.

e.

Check

for

open

high-voltage

rectifier

(D403).

MONITOR

-

·TROUBI..ESHOOTING

GUIDE

05/11/81

Page

2-12

2.

Reduced

horizontal

scan.

a.

Check

base

drive

at

Q401.

If

not

OK,

check

oscillator

(Ic400)

and

drive

(Q400, T400)

circuits.

b.Check

yoke and yoke

series

components.

3.

Loss

of

horizontal

sync.

a.

Check

for

sync

pulse

from Logic

board.

If

not

present,

troubleshoot

to

Logic

board.

b.

Check

horizontal

oscillator

(IC400).

4.

Loss

of

horizontal

sync

or

drift

after

warmup.

a.

Check

for

faulty

C409, C403,

or

other

capacitor

in

the

oscillator

cir-

cuit.

b.

Check

horizontal

oscillator

(IC400).

5.

Blooming

raster

(large

raster;

low

high

voltage).

a.

Check

for

proper

drive

at

base

of

Q401.

b.

Check

for

shorted

high-voltage

rectifier

(D403).

c.

Check

for

bad

retrace

cap (C410)

or

S-cap

(C415).

6.

Compressed

characters

at

right

side

of

raster.

a.

Check

for

proper

drive

at

base

of

Q401.

b.

Check

for

phase

proble~

at

IC400

4.

c.

Check

the

linearity

coil

(L407).

d.

Check

the

other

yoke

series

components.

MONITOR

-

REPLACEMENT

PARTS

03/08/82

PAGE

2-13

REPLACEMENT

PARTS.

The

Monitor board

is

built

in

115VAC

and

230VAC

versions.

Where

part

differences

exist,

the

230VAC

parts

are

identified

by

the

label

112.

REPLACEMENT

BOARDS

210402A

S/A

MON

BD

8500

(115VAC)

210403B

Sf

A

MON

BD

8598

(230VAC)

112

INTEGRATED

CIRCUITS

Z100

180113

IC

MC1391P

Z200

180104

IC

555

Z400

180113

IC

MC1391P

z600 180104

IC

555

TRANSISTORS

Q100

170035

XSTR

MPSA70

Q101

170035

XSTR

MPSA70

Q102

170021

XSTR

MPSA20

Q103

110028

XSTR

MPSU05

Q104

110032

XSTR

NSDU56

Q105

110040

XSTR

SJE2319

Q105tl2

110041

XSTR

MJ12004

Q106

110021

XSTR

MPSA20

Q101

170027

XSTR

MPSA20

Q108

170035

XSTR

MPSA10

Q109

170021

XSTR

MPSA20

Q110

170027

XSTR

MPSA20

Q111

110035

XSTR

MPSA70

Q200

170027

XSTR

MPSA20

Q201

110021

XSTR

MPSA20

Q202

170031

XSTR

92PU51

Q203

170034

XSTR

2N5496

Q204

110033

XSTR

2N6109

Q205

110032

XSTR·NSDU56

Q201

170024

XS'l'R

MPSA

13

.

Q300

110027

XSTR

MPSA20

Q301

110035

XSTR

MPSA70

Q302

170021

XSTR

MPSA20

Q303

. 110035

XSTR

MPSA10

Q304

110031

XSTR

MPSU03

Q305

110036

XSTR

2N3104

Q400

110032

XSTR

NSDU56

Q401

110038

XSTR

2N6308

Q402

110039

XSTR

BUX86

Q600

110035

XSTR

MPSA10

Q601

110021

XSTR

MPSA20

MONITOR

-

REPLACEMENT

PARTS

DIODES

D100

D100il2

D101

0102

D103

0104

D105

D106

0107

D108

D109

D111

D112

0113

0200

0201

0202

0203

D300

D301

D400

D401

D402

160064

BRIDGE

VS447

160066

BRIOGE

VS847

160004

DIODE

2N4148

160004

DIODE

2N4148

160004

DIODE

2N4148

160041

DIODE

BY206

160041

DIODE

BY206

160046

DIODE

MR810

160053

DIODE

MR850

160046

DIODE

MR810

160046

DIODE

MR810

160041

DIODE

BY206

160042

DIODE

BY208

160043

DIODE

1N4749

160062

DIODE

1N5236

160048

DIODE

1N4448

160033

DIODE

1N4003

160033

DIODE

1N4003

160038

DIODE

1N4004

160004

DIODE

lN4148

160044

DIODE

MR818

160044

DIODE

MR818

160041

DIODE

BY206

RESISTORS

(All

rstrs

1/4W

unless

specified)

RV100

RV200

RV202

RV301

Rv400

RV401

Rv403

RV500

R100

R100fl2

R101

R10H/2

R102

R102/12

R103

R103/12

R105

R110

R112

R113

R113fl2

R114

R114/12

R115

R116

R1161F2

150g29

TMPT

100

150926

TMPT

10K

150925

TMPT

5K

150925

TMPT

5K

150922

POT

2M

150926

TMPT

10K

150925

TMPT

5K

150934

TMPT

250K

150106

RSTR

68K

1500g8

RSTR

33K

150315

RSTR

150K

1/2W

150323

RSTR

330K

1/2W

151304

RSTR

22K

2W

GL

151302

RSTR

47K

2W

GL

151301

RSTR

15K

3W

GL

151302

RSTR

41K

3W

GL

151101

RSTR

4.7

1W

GL

150034

RSTR

68

150081

RSTR

6.2K

151306

RSTR

180

2W

GL

150544

RSTR

330

1W

150022

RSTR

22

150034

RSTR

68

150231

RSTR

47

1/2W

151300

RSTR

1K

2W

GL

150302

RSTR

41K

3W

GL

(2

in

parallel)

03/08/82

PAGE

2-14

MONITOR

-

REPLACEMENT

PARTS

R117

R117tJ2

R118

R119

R120

R121

R122

R123

R124

R126

R127

R128

R129

R130

R131

R132

R133

R134

R135

R136

R137

R138

R139

R140

R141

R142

R143

R144

R145

R146

R147

R148

R151

R152

R153

R157

R158

R159

R200

R202

R203

R204

R205

R206

R207

R208

R209

R210

R212

R213

R214

R215

R216

R217

R218

151303

RSTR

2.6

1W

GL

151500

RSTR

5.0

3W

GL

150271

RSTR

2.2K

1/2W

150048

RSTR

270

150562

RSTR

1K

1W

150114

RSTR

150K

150090

RSTR

15K

150048

RSTR

270

150058

RSTR

680

150130

RSTR

680K

150052

RSTR

390

150108

RSTR

82K

150090

RSTR

15K

150062

RSTR

1.0K

150100

RSTR

39K

150086

RSTR

10K

150054

RSTR

470

150050

RSTR

330

150062

RSTR

1.0K

150126

RSTR

470K

150038

RSTR

100

150088

RSTR

12K

150078

RSTR

4.7K

150084

RSTR

8.2K

150086

RSTR

10K

150239

RSTR

100

1/2W

150167

RSTR

2.2

150498

RSTR

.47

1W

150223

RSTR

22

1/2W

150090

RSTR

15K

150086

RSTR

10K

150167

RSTR

2.2

150098

RSTR

33K

150122

RSTR

330K

150014

RSTR

10

150090

RSTR

15K

150094

RSTR

22K

150134

RSTR

1.0M

150251

RSTR

330

1/2W

150114

RSTR

150K

150064

RSTR

1.2K

150062

RSTR

1.0K

150038

RSTR

100

150062

RSTR

1.0K

150102

RSTR

47K

150062

RSTR

1.0K

150086

RSTR

10K

150073

RSTR

3.0K

150062

RSTR

1.0K

150014

RSTR

10

150106

RSTR

68K

150235

RSTR

68

1/2W

150197

RSTR

1.0

1/2W

150253

RSTR

390

1/2W

150253

RSTR

390

1/2W

03/08/82

PAGE

2-15

Ann Arbor AMBASSADOR User manual

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