Apple Twopage Monochrome Monitor Service Manual

K

Service Source

Apple Two-Page Mono

Monitor

K

Service Source

Basics

Two-Page Monochrome Monitor

Basics Monitor Distortion - 1

Monitor Distortion

Overview

All large-screen monitors
are susceptible to
distortions caused by
environmental conditions.

Ideal Raster

These distortions are
usually not visible on
monitors with smaller
screens.

Raster Shifted Up

and Left

Raster Shifted Right

Basics Monitor Distortion - 2

Important:

set to factory specifications
may appear distorted when
set up in a new environment.

Common environmentally­caused distortions are shown
on this and the following
cards. Always check first for
environmental causes before
attempting to repair or
adjust a monitor with a
distorted raster.

Even monitors

Basics Monitor Distortion - 3

Environmental
Influences

The following environmental
conditions may distort the
raster of a Two-Page
Monochrome Monitor:

• Proximity to metal
objects, such as metal

Right Edge Not Straight

Left Side Bowed Out Right Side Bowed In

desks, file cabinets, and
bookshelves. Metal
objects affect the earth’s
magnetic field. Earth
magnetism usually
distorts only the edges of
the screen.

Basics Monitor Distortion - 4

• Fluorescent lights, other
monitors, or electronic
appliances such as coffee
makers and copy
machines. These objects
cause dynamic raster
distortion, that is,
movement or jitter of the
image.

Basics Monitor Distortion - 5

Troubleshooting

Upper-Right Corner Rounded

Left Edge S-Shaped Raster Tilted Right

Important:

swapping cannot fix a
monitor with
environmental distortion
problems, and adjusting a
monitor with such
problems alters the factory
settings.

Note:

shifted up/down or right/
left only, adjust it using the
centering controls. If you
then move the monitor, you
may need to readjust the
centering controls.

Module

If the monitor has

Basics Monitor Distortion - 6

Before adjusting a monitor
with a distorted raster, try
the following:

• Swivel or move the
monitor, or

• Remove the monitor from
the building and recheck
it in another location.

If the display changes (for
better or worse) when you
move it to another location,
the environment is the
source of the problem.
Relocate the monitor or
remove the distortion­causing object.

Basics Monitor Distortion - 7

If the display does not change
when you move the monitor
to another location,
continue troubleshooting
the problem (refer to
Troubleshooting/Symptom
Charts).

K

Service Source

Specifications

Apple Two-Page Monochrome

Monitor

Specifications Characteristics - 2

Characteristics

Picture Tube

Screen Resolution

Scan Rates

21-in. diagonal screen (20-in. viewable image)
Phosphor EIA Type P4 (white)
Flat, square, high-contrast, antiglare surface

1,152 x 870 lines; 77 dpi
Displays up to 16 grays with 512K of video RAM

Vertical refresh rate: 75 Hz
Horizontal scan rate: 68.7 kHz
Dot clock: 100 MHz

Specifications Characteristics - 3

Active V ideo Display Area

Input Signal

15 in. by 11.3 in.
(381 mm by 287 mm)

Video: analog; RS–343 standard

Specifications Controls - 4

Controls

User Controls

Rear panel: power switch
Right side: brightness and contrast controls

Specifications Physical and Electrical - 5

Physical and Electrical

Power Supply

Size and Weight

Monitor Stand

Universal power supply
Voltage: 90–270 VAC, self-configuring
Frequency: 47–63 Hz
Power: 95 W maximum

Height: 15.7 in. (399 mm)—add 3.2 in. (81 mm) for integrated

stand
Width: 19.5 in. (495 mm)
Depth: 17.4 in. (442 mm)
Weight: 55 lb. (25 kg)

Integrated, tilt-and-swivel stand

Specifications Operating Environment - 6

Operating Environment

Temperature

Humidity

Altitude

50°F–95°F (10°C–35°C)

90% maximum, noncondensing

10,000 ft. (3,048 m) maximum

K

Service Source

Troubleshooting

Apple Two-Page Monochrome

Monitor

Troubleshooting General/ - 1

General

The Symptom Charts included in this chapter will help you
diagnose specific symptoms related to your product. Because cures
are listed on the charts in the order of most likely solution, try
the first cure first. Verify whether or not the product continues to
exhibit the symptom. If the symptom persists, try the next cure.
(Note: If you have replaced a module, reinstall the original module
before you proceed to the next cure.)

If you are not sure what the problem is, or if the Symptom Charts
do not resolve the problem, refer to the Flowchart for the product
family.

For additional assistance, contact Apple Technical Support.

Troubleshooting Symptom Charts/No Raster - 2

Symptom Charts

No Raster

No raster, LED off 1 Check AC power cord connections.

2 Check internal power connectors.
3 Replace blown fuse.
4 Replace power supply.
5 Replace on/off switch filter assembly.
6 Replace deflection board.

No raster, LED on 1 Adjust brightness and contrast knobs.

2 Verify that video card in computer is working properly.
3 Check power supply and deflection board connections.
4 Check CRT socket connectors.
5 Replace video board.
6 Replace deflection board.
7 Replace CRT and yoke assembly.

Troubleshooting Symptom Charts/Geometry - 3

Geometry

Raster size too short,
tall, narrow, or wide

Raster not centered 1 Verify that distortion is not due to environmental conditions.

Bad vertical linearity 1 Adjust vertical linearity control.

Bad horizontal
linearity

1 Adjust horizontal-size and vertical-size controls.
2 Replace deflection board.
3 Replace CRT and yoke assembly.

Move monitor to another location.
2 Adjust horizontal-shift and vertical-shift controls.
3 Replace video board.

2 Replace deflection board.

1 Adjust horizontal linearity control.
2 Replace deflection board.

Troubleshooting Symptom Charts/Synchronization - 4

Synchronization

Single horizontal or
vertical line appears
on screen

Picture breaks into
diagonal lines

Picture rolls
vertically

1 Check yoke connectors.
2 Check CRT socket connectors.
3 Replace deflection board.
4 Replace CRT and yoke assembly.

1 Connect another monitor to computer. Switch on monitor to

verify that computer produces video signal.
2 Check connections between video board and deflection board.
3 Replace deflection board.
4 Replace video board.

1 Verify that video card in computer is working properly.
2 Check connections between video board and deflection board.
3 Replace deflection board.
4 Replace video board.

Troubleshooting Symptom Charts/Video - 5

Video

Picture is too dark or
too bright

Contrast/brightness
unadjustable

1 Adjust contrast and brightness knobs.
2 Verify that video card in computer is working properly.
3 Check connection between contrast/brightness assembly and

video board.
4 Perform video adjustments.
5 Replace video board.
6 Replace contrast/brightness assembly.
7 Replace CRT and yoke assembly.

1 Check connection between contrast/brightness assembly and

video board.
2 Replace contrast/brightness assembly.
3 Replace video board.
4 Replace deflection board.
5 Replace CRT and yoke assembly.

Troubleshooting Symptom Charts/

(Continued)

Out of focus 1 Check CRT socket connectors.

2 Check connections between video board and deflection board.
3 Perform focus adjustment.
4 Check screen brightness with a light meter. If reading is

“10” or higher, perform the cutoff and screen luminance

adjustments.
5 Replace video board.
6 Replace deflection board.
7 Replace CRT and yoke assembly.

(Continued)

- 6

Troubleshooting Symptom Charts/Miscellaneous - 7

Miscellaneous

Picture jitters or
flashes

At a resolution of
1152x870, jitter or
a wavy image appears
on right side, left
side, or entire screen

Black spots on screen
(burnt phosphors)

1 Check all grounding cable connections.
2 Confirm that adjacent computer equipment is properly

grounded. Move electrical devices away from the monitor and

temporarily shut off all fluorescent lights.
3 Check connections between video board and deflection board.
4 Replace deflection board.

Note:

This symptom occurs with Power Macintosh 9600
computers using an Apple/IMS video card with any display set at
1152x870 screen resolution. The computer and the display are
working properly. However, video cards with serial numbers
lower than Fx705xxx should be replaced. Apple’s service stock
has been inspected and upgraded, so replacement video boards
should not exhibit this symptom.

Check the serial number on the video card. If it is lower than
Fx705xxx, replace the video card with a new one (Apple service
part number 661-1409).

Replace CRT.

Troubleshooting Symptom Charts/Monitor Stand - 8

Monitor Stand

Monitor stand does not
swivel

Monitor stand does not
tilt

1 Verify that “Front” indicator on tilt/swivel mechanism

aligns with “Front” indicator on base of monitor stand.

2 Verify that snap lock assembly on bottom of monitor stand is

in place.

1 Verify that plastic plug is in snap lock assembly.
2 Verify that snap lock assembly on bottom of monitor stand is

in place.

K

Service Source

T ak e Apart

Apple Two-Page Monochrome

Monitor

Take Apart Swivel Stand - 1

Swivel Stand

No preliminary steps are
required before you begin
this procedure.

Note:

Remove the tilt­swivel stand before you
remove the CRT.

1 Tilt the monitor onto its

left side.

2 Slide the monitor stand

forward toward the
bezel.

Swivel Stand

Take Apart Swivel Stand - 2

3 With one hand, slightly

lift up the monitor and
rotate the base of the
stand until you can reach
the three screws that
secure the stand to the
chassis.

Take Apart Swivel Stand - 3

4 Remove the three

mounting screws.

5 Slide the monitor stand

back and remove it from
the chassis.

Take Apart Rear Cover - 4

Rear Cover

No preliminary steps are
required before you begin
this procedure.

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

1 Remove the four cover

mounting screws.

2 Pull the rear cover off

the bezel.

Rear Cover

This product

Take Apart Access Cover - 5

Access Cover

Before you begin, remove
the rear cover.

±

Access

Cover

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

1 Remove the six mounting

screws and lockwashers
that hold the access
cover in place.

2 Lift the access cover off

the chassis.

This product

Take Apart Video Board - 6

Video Board

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Video Board

Warning:

grounding wriststrap until
after discharging the CRT.

Never use a

Take Apart Video Board - 7

Disconnect the following
cable connectors from the
video board:

• 13-wire (white)

J604

J601

cable from J601

• 11-wire (white)
cable from J602

• 6-wire (white) cable
from J603

• 2-wire (red/orange)
cable from J604

J602

J603

Take Apart Video Board - 8

Caution:

the connectors by
pulling on the connector
cables. If the connectors
are difficult to
disconnect, slip a
jeweler’s screwdriver
between the two halves
of the connector and
carefully pry the halves
apart.

Do not remove

Take Apart Video Board - 9

1 Remove the hex nut,

washer, and green
grounding wire from the
metal post on the floor of
the monitor.

2 Pull the CRT socket off

the neck of the CRT.

Take Apart Video Board - 10

3 Remove the four screws

that secure the video
board to the chassis.

4 Carefully lift the video

board up and out of the
chassis.

Take Apart Deflection Board - 11

Deflection Board

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

• Remove the anode cap

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart Deflection Board - 12

1 Remove the four screws

that secure the deflection
board to the chassis.

Deflection Board

Take Apart Deflection Board - 13

2 Disconnect the following

cable connectors from
the deflection board:

J402

• 11-wire (white)
from J402

J301

• 3-wire (red/blue)
from J202

• 2-wire (red/orange)
from J501

J202

• 5-wire (rd/blk/or/
yel) from J201

• 13-wire (white)
from J401

J501

J401

J403

J201

• 2-wire (gray) from
J403

• 2-wire (yellow/
black) from J301

Take Apart Deflection Board - 14

Caution:

the connectors by
pulling on the connector
cables. If the connectors
are difficult to
disconnect, slip a
jeweler’s screwdriver
between the two halves
of the connector and
carefully pry the halves
apart.

Do not remove

Take Apart Deflection Board - 15

3 Locate the bleeder

resistor on the floor of
the monitor.

4 If the resistor is cigar-

shaped, slide the
resistor sideways, pull
up slightly on the plastic
clip, and remove the
resistor.

Cigar-shaped Resistor

5 If the resistor is box-

shaped, remove the
screw that holds the
resistor. Slide the
resistor forward and
release it from the metal
bracket.

Box-shaped Resistor

Take Apart Deflection Board - 16

6 Remove the anode wire

from the plastic cable
clamp.

7 Lift the deflection board

up and out of the chassis.

Take Apart Power Supply - 17

Power Supply

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart Power Supply - 18

1 Remove the two screws

that fasten the power
supply to the chassis.

Power SupplyPower Supply

Take Apart Power Supply - 19

Power Supply

2 Disconnect the three-

wire connector from the
top of the power supply
and the five-wire
connector from the
front of the power
supply.

3 Carefully lift the power

supply from the chassis.

Take Apart Fuse - 20

Fuse

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

Fuse

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart Fuse - 21

Note

: Some units with serial
numbers between
43661GXW and 44718HQX
have 1.6 A for the fuse on
the power supply board.
This amperage is incorrect.
The correct value is 2.5 A.

Using your fingers or a flat­blade screwdriver, gently
pry up one end of the fuse
and remove the fuse from
the holder.

Take Apart On/Off Switch - 22

On/Off Switch

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

On/Off
Switch

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart On/Off Switch - 23

1 Remove the three hex

nuts, the washers, and
the three grounding
wires from the metal
post on the floor of the
monitor.

2 Disconnect the 3-wire

connector from the top of
the power supply.

Take Apart On/Off Switch - 24

3 Pull the plastic knob off

the on/off switch.

4 Remove the two screws

that secure the on/off
switch to the chassis.

5 Remove the two screws

that secure the A/C
power socket to the
chassis.

6 Lift out the on/off switch

assembly.

Take Apart Contrast/Brightness Assembly - 25

Contrast/ Brightness Assembly

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

Contrast/Brightness

Assembly

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart Contrast/Brightness Assembly - 26

1 Pull off the contrast and

brightness control
knobs.

2 Remove the four screws

that secure the deflection
board to the chassis. Pull
the logic board slightly
away from the side of the
chassis.

Take Apart Contrast/Brightness Assembly - 27

3 Disconnect the six-wire

cable from connector
J603 on the video board.

J603

Take Apart Contrast/Brightness Assembly - 28

4 Remove the two hex nuts

and pull the contrast­brightness assembly off
the chassis.

Take Apart Bezel - 29

Bezel

Bezel

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart Bezel - 30

1 Remove the four hex

nuts that secure the
bezel to the chassis.

2 Pull the bezel off the

chassis.

Take Apart Bezel - 31

3 Remove the hex nut that

secures the LED and the
black paper baffle to the
bezel.

Take Apart CRT - 32

CRT

CRT

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

• Remove the anode cap

• Remove the bezel

• Remove the swivel stand

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart CRT - 33

1 Disconnect the following

cable connectors from
the deflection board:

• 3-wire (CRT neck)
from J202

• 2-wire (CRT neck)

J301

J202

from J301

Take Apart CRT - 34

2 Pull the CRT socket off

the neck of the CRT.

Take Apart CRT - 35

3 While supporting the

CRT with one hand,
remove the four screws
and washers that secure
the CRT to the chassis
frame. Save the washers
to use on the
replacement CRT.

±

Warning:

handle the CRT by the
neck!

4 Carefully grasp the sides

of the CRT and lift the
CRT out of the chassis.

Do not

Take Apart CRT - 36

5 Place the CRT face-down

on a soft, protective
surface.

6 Remove the grounding

strap and the spring.

Grounding Strap

Spring

Save them to use on the
replacement CRT.

±

Warning:

is cracked or broken,
refer to the CRT
disposal instructions in
Bulletins/Safety.

If the CRT

Take Apart LED Assembly - 37

LED Assembly

Before you begin, do the
following:

• Remove the rear cover

• Remove the access cover

• Discharge the CRT

• Remove the anode cap

• Remove the bezel

• Remove the swivel stand

• Remove the CRT

±

LED Assembly

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Take Apart LED Assembly - 38

1 Disconnect the LED

cable from the

Deflection Board

deflection board.

2 Remove the hex nut that

secures the green
grounding wire to the
inside of the chassis. Lift
out the LED assembly.

LED

Cable

K

Service Source

Adjustments

Apple Two-Page Monochrome

Monitor

Adjustments Geometry - 1

Geometry

Before you begin, remove
the following:

• Rear cover

• Access cover

±

Horizontal

Linearity

Control

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

Adjustment

Controls

This product

Adjustments Geometry - 2

Warning:

make the adjustments from
the rear of the computer,
position a mirror to view
the computer screen. Do not
reach around the computer
to adjust the controls.

Note:

should always be performed
whenever you replace the
CRT, deflection board, or
video board.

Because you must

Geometry adjustments

Adjustments Geometry - 3

Horizontal Linearity

1 Use Display Service

Utility to display the
Crosshatch II (white
background) test
pattern.

Horizontal

Linearity

Control

Caution:

adjustment tool is the
only tool that can be used
to adjust the Horizontal
Linearity control! Use
of any other tool may
damage the adjustment
control coil core or
cause a short in the
monitor’s circuitry.

The linearity

Adjustments Geometry - 4

2 Using the linearity

adjustment tool, adjust
the horizontal linearity
control until the raster
is as wide as possible.

3 Using the linearity

adjustment tool, slowly
adjust the horizontal
linearity control until
the left and right halves
of the raster are the
same distance from the
center of the screen.

• To measure the left
half of the raster,
place a flexible ruler

Horizontal

Linearity

Control

against the screen

Adjustments Geometry - 5

directly over the
black horizontal line.
Align the zero mark of
the ruler with the left
edge of the raster.
Note the measurement
at the point where the
two black lines
intersect.

• To measure the right
half of the raster,
align the zero mark of
the ruler where the
two black lines
intersect. Note the
measurement at the
right edge of the
raster.

Adjustments Geometry - 6

4 Using the plastic

alignment tool, slowly
adjust the horizontal
size control until the
raster is 15 inches (±
1/8") or 381 mm (± 3
mm) wide.

5 Verify that the left and

right halves of the
raster are still the same
distance from the center
of the screen. If
necessary, adjust the
horizontal linearity

Horizontal Size

control.

Adjustments Geometry - 7

6 Verify that the boxes on

both the left and right
sides of the screen are
the same size as the
boxes in the center of the
screen. If they are not
the same size, perform
the next step.

±

Warning:

monitor operates at
extremely high voltages.
To prevent electrical
shock, use a plastic
alignment tool to set the
3-position switch.
Avoid touching the
heatsink or any other

The

Adjustments Geometry - 8

part of the monitor.

±

Warning:

not use a plastic
alignment tool, turn off
the power before
reaching inside the
chassis and adjusting
the switch. Then turn on
the power and view the
monitor screen.

If you do

Adjustments Geometry - 9

7 Using the plastic

alignment tool, set the
3-position switch to the
lowest of the three
settings and recheck the
relative size of the
boxes. Repeat for all
three positions of the
switch and select the
best position.

3-Position Switch

Adjustments Geometry - 10

8 Using the plastic

alignment tool, slowly
adjust the horizontal
size control until the
raster is 15 inches (±
1/8") or 381 mm (± 3
mm) wide.

9 Verify that the raster is

centered on the screen. If
necessary, adjust the
horizontal shift control.

Horizontal Size

Horizontal Shift

Adjustments Geometry - 11

Vertical Linearity

1 Use Display Service

Utility to display the
Crosshatch I or
Crosshatch II test
pattern.

2 Using the plastic

alignment tool, adjust
the orange capacitor at
C306 until the top two
rows of boxes are the
same height.

Vertical

Linearity

Adjustments Geometry - 12

3 Using the plastic

alignment tool, adjust
the vertical linearity
control until the top and
bottom rows of boxes are
the same height.

4 Use Display Service

Utility to display the
Full White Screen test
pattern.

5 Using the plastic

alignment tool, adjust
the vertical shift control
until the white raster is

Vertical Shift

vertically centered.

Adjustments Geometry - 13

6 Use Display Service

Utility to display the
All-White Screen test
pattern.

All-White Screen

7 Using a plastic alignment

tool, adjust the vertical
size control until the
white raster is 11 5/
16 inches (± 1/8”) or

287.3 mm (± 3 mm)

high.

Vertical Size

Adjustments Geometry - 14

Focus

1 Use Display Service

Utility to display the
Focus test pattern.

2 Using a plastic

screwdriver, adjust the
static focus control for
the best focus in the box
at the center of the
screen.

Static

Focus

Adjustments Geometry - 15

3 Using a plastic

screwdriver, adjust the
horizontal focus control
for the best focus in the
box at the left and right
sides of the screen.

4 Using a plastic

screwdriver, adjust the
vertical focus control
for the best focus in the
box at the top and bottom
center of the screen.

5 Repeat the adjustments

until you have attained

Horizontal

Focus

Vertical

Focus

the best focus possible.

Adjustments Video - 16

Video

Brightness

Contrast

Cutoff

Brightness

Subcontrast

Range

Before you begin, remove
the following:

• Rear cover

• Access cover

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT safety in
Bulletins/Safety.

This product

Adjustments Video - 17

Warning:

make adjustments from the
rear of the computer,
position a mirror to view
the computer screen. Do not
reach around the computer
to adjust the controls.

Note:

should always be performed
whenever you replace the
CRT, deflection board, or
video board.

Because you must

Video adjustments

Adjustments Video - 18

1 Switch off the power and

remove the video cable
from the back of the
monitor.

All-White Screen

2 Set the external (user)

contrast knob to
maximum (turn fully
clockwise) and the
brightness knob to the
center (detent) position.

Brightness
Contrast

Adjustments Video - 19

3 Using the plastic

screwdriver, adjust the
cutoff control to
minimum (turn fully

All-White Screen

counterclockwise).

4 Switch on the power and

wait 20 minutes for the
monitor to warm up.

5 Use Display Service

Utility to display the
All-White Screen test
pattern.

Cutoff

Adjustments Video - 20

Note:

The Cutoff
adjustment should be
performed in a dimly lit
room after the monitor

All-White Screen

has been on for at least
20 minutes.

6 Using the plastic

screwdriver, turn the
cutoff control clockwise
until a white raster just
appears, then turn
counterclockwise until
the raster just fades to
black.

7 Switch off the power and

reconnect the video
cable.

Cutoff

Adjustments Video - 21

8 Switch on the power.

Note:

If the power is
turned off for more than
a few seconds, you must
wait for another 20
minutes for the monitor
to warm up.

Adjustments Video - 22

9 Use Display Service

Utility to display the
Gray Bars test pattern.

10 Using a plastic alignment

tool, adjust the cutoff
control until the
leftmost bar (darkest)
is black and the next bar
is barely distinguishable
from the black bar.

Cutoff

Adjustments Video - 23

All-White Screen

Sub-contrast

Important:

Readings
from light meters R77,
L–248, and 246 differ.
Please note which meter
you are using before
making adjustments.
(See “Light Meter
Setup.”)

11 Using Display Service

Utility, display the All­White Screen test
pattern.

Adjustments Video - 24

12 Using the light meter and

a two-inch plastic
screwdriver, adjust the
sub-contrast control
until you get 31 foot
lamberts (± 3 foot
lamberts), which on the
light meter is

• Model R77: 23 on the

bottom scale

• Model L-248: middle

of the 10 scale

• Model 246: 23 on the

red scale

Adjustments Video - 25

Brightness

Knob

Brightness

Range

All-White Screen

Important:

Over time,
light meter tolerances
can vary. If you doubt
your meter’s accuracy,
verify the readings with
a known-good light
meter or photometer.

13 Set the external (user)

brightness knob to
maximum (turn fully
clockwise).

Adjustments Video - 26

14 Using the plastic

screwdriver, adjust the
brightness range
control until you get 31
foot lamberts (± 3 foot
lamberts), which on the
light meter is

• Model R77: 23 on the

bottom scale

• Model L-248: middle

of the 10 scale

• Model 246: 23 on the

red scale

15 Reset the brightness

knob to the center
(detent) position.

Adjustments Light Meter Setup - 27

Light Meter Setup

This topic covers setup for
three light meter models:
R77, L-248, and 246.
Model R77 (Apple part
number 076-0310) is the
newest model available.

Model R77

The R77 light meter is
capable of reading luminance
from 10 to 1,000
footcandles (fc).

Before you begin, remove
the 10X multiplier plate

Adjustments Light Meter Setup - 28

from the lens.

Three scales are shown on
the light meter:

• 200-1000 fc

• 50-250 fc

• 10-50 fc

Because display screen
luminance typically ranges
from 10 to 50 fc, take
readings from the bottom
scale only.

Adjustments Light Meter Setup - 29

To measure a display
screen’s luminance,

1 Set the scale switch to

the bottom position (to
set up the 10-50 fc
scale).

2 Place the lens against the

middle of the screen and
read the bottom scale.

Note:

When the light meter
is not in use, slide the scale
switch to its top position,
and store the meter in its
protective case.

Important:

light meter is giving false

If you suspect the

Adjustments Light Meter Setup - 30

readings, verify the
readings with a known-good
light meter or photometer.
Also check the age of the R77
light meter by its four-digit
manufacturing date stamp
(such as 0398 for March

1998).

Caution:

meter can permanently
damage its accuracy. A
shock-damaged meter might
read incorrectly or its
pointer may not drop to
zero.

Dropping the

Adjustments Light Meter Setup - 31

Side Switch

Scale

Lens

Read Button

Red Area

Model L-248

1 Press the red button on

the back of the light
meter. If the reading is
out of the red area,
replace the battery.

2 Move the side switch to

its upper position so that
the scale reads 10
through 18.

3 Uncover the lens of the

meter.

4 Place the lens against the

middle of the screen and
press the read button to
read the scale.

Adjustments Light Meter Setup - 32

Model 246

1 Remove the metal slide,

Lens

if installed, from the
top of the light meter.

Swivel Head

Scale

2 Install the white lens

with the red dot.

3 Rotate the swivel head

so the lens of the meter
faces the monitor.

4 Place the lens against the

middle of the screen and
read the scale.

K

Service Source

Exploded V ie w

Apple Two-Page Monochrome

Monitor

Exploded View 1

Access Cover

949-0223
Bezel

590-0393

Power Supply

Cable 6-Pin

590-0395

12-Pin Cable

590-0391

LED and Cable

Assembly

905-0007

Contrast/

Brightness

Assembly

661-0453

Power

Supply

941-0016
Fuse

949-0224
Rear Cover

076-0320

CRT

Assembly

590-0397

3-Pin Cable

590-0398

14-Pin Cable

661-0452
Video Board

661-0451
Deflection
Board

956-0012
Screw Knob Set

937-0040
On/Off Switch
Filter Assembly

815-0558
Tilt/Swivel
Monitor Stand

590-0371
Power
Cable

590-0615
Video
Cable