DEC VR14, VR17 User Manual

VR14/VR17

CRT

display

monitor

user's

manual

EK-VR14-0P-005

VR14/VR17

monitor

user's

CRT

display

manual

digital

equipment

corporation:.

maynard.

massachusetts

1 st Edition, April 1971

Printing (Rev) June 1971

2nd

Printing (Rev) June 1972

3rd 4th

Printing (Rev) January 1973

5th

Printing, July 1973 2nd Edition, December 1973 7th

Printing, November 1974

The material in this manual purposes and

Digital Equipment sibility for any errors which may appear in this manual.

is

subject to change without notice.

Corporation assumes no respon-

Printed

is

in U.S.A.

for infonnational

The following are trademarks Corporation, Maynard, Massachusetts:

DEC

FLIP

CHIP

DIGITAL

of

Digital Equipment

PDP

FOCAL

COMPUTER

LAB

CONTENTS

Page

CHAPTER 1

1.1

1.2

1.3

CHAPTER 2

2.1

2.2

2.3

2.4

2.5

CHAPTER 3

3.1

3.2

3.3

3.4

3.5

3.6

3.6.1

CHAPTER 4

4.1

4.2

4.2.1

4.2.2

4.3

4.3.1

4.3.2

4.3.3

4.3.4

4.3.5

GENERAL INFORMATION INTRODUCTION

SPECIFICATIONS

......................................

.....

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BLOCK DIAGRAM DESCRIPTION

OPERATION INSTALLATION

FRONT PANEL CONTROLS REAR

PANEL CONNECTORS

INTERNAL

CONTROLS

......................................

................................

...............................

..................................

INPUT SIGNAL REQUIREMENTS

THEORY OF OPERATION X-

AND Y- DEFLECTION CIRCUITS PLUS AND MINUS CRT ELECTRODE VOLTAGES

VOLTAGE POWER SUPPLY

HIGH W682 AND W684 INTENSITY LIGHT PEN AMPLIFICATION

375 Light

LOW

VOLTAGE REGULATED SUPPLY

CIRCUITS

Pen

.....................................

.............................

...............................

MAINTENANCE PREVENTIVE MAINTENANCE

TROUBLESHOOTING

No Picture

.......................................

Faulty Picture

ASSEMBLY

REPLACEMENT INSTRUCTIONS

Deflection

Heat

...................................

.....................................

Sink Removal

..............................

7007165 Power Regulator Assembly Removal Regulator Heat Sink Removal Yoke and CRT Removal

................................

High Voltage Supply Removal

.............................

..........................

.............................

.........................

......................

.............................

........

.............................

...............

. . . . . . . . . . .

1-1

..

1-1 1-3

2-1 2-1 2-2 2-2 2-2

"

3-1 3-5

" 3-6

3-6 3-10 3-13 3-14

4-1

4-5

..

4-7

4-9

4-9 4-11

CHAPTER 5

APPENDIX A

APPENDIX B

APPENDIXC

ENGINEERING DRAWINGS

POWER SUPPLY TROUBLESHOOTING

DEFLECTION

A225 REPAIR

AMPLIFIER TROUBLESHOOTING

iii

ILLUSTRA

nONS

Figure No.

1-1 1-2 2-1 2-2 3-1 3-2

3-3 3-4 3-5 3-6 3-7

3-8 4-1 4-2

4-3

4-4

4-5

Table No.

Block Diagram VRI4L/VRI7L Input

Power Jumper

Locations

of

Internal Controls

ofVR14

Block Diagram

Without Light Pen

.....

X and Y Deflection Circuit . .

G836

Circuit Board,

Part

of

the 7007165 Power Regulator Assembly Intensity Amplifier W682, W684 Intensity G838

Circuit Diagram

VRI4L/VRI7L

Control

Brightness and Contrast Control Ligh t Pen Amplifier Light

Pen Pulse Timing,

VRI4/VRI7

Interior View

Deflection Heat Sink Removal

Circuit Schematic

...........

............

........

G840

Module

....

.. 7007165 Power Regulator Assembly 7007165 Removal

.....

Regulator Heat Sink Removal

Title

.

. .

TABLES

Title

Option

. .

.

Page

1-4

1-5 2-1 2-6 3-3

3-7 3-9

3-10

3-11

3-12 3-13 3-14

4-3

4-6 4-7 4-8

4-10

Page

1-1 2-1 2-2 2-3 3-1 4-1 5-1 5-2

VR14

and

VR17

Configurations . J 17 Rear J18 Control Settings Brightness VRI4/VRI7

VR14 VR17

Connector Pin Assignments

Rear Connector Pin Assignments

........

Control

.......

Voltage Check Points Engineering Drawings Engineering Drawings

...

1-1 2-3 2-5

. .

2-7

3-12

4-2 5-1 5-1

iv

WARNING

Maintenance procedures should be performed by qualified service personnel only.

High

voltages are present within the unit and, under certain conditions, are potentially dangerous.

All

electrical safety precautions

must be observed.

Inherent implosion protection

is

employed in the CRT design; however, the tube may be damaged

if

it

is

subjected to rough treatment

or

dropped while being removed from or installed

in the display. Exercise caution during these

operations.

CHAPTER

1

1.1 INTRODUCTION The VR14 and VR17 are completely self-contained CRT display monitors that require only analog X-and Y-position information and an intensity input, to generate sharp, bright displays. The VR14 and VR17 are electrically identical. The VR17, however, has a larger display screen

(12

(17 inches diagonal) than the VR14 This necessitates a correspondingly larger enclosure, and a CRT support bracket for the VR17. Except for the CRT itself,

both

VR14 and VR17 are composed state circuits, utilizing high-speed magnetic deflection to enhance brightness and resolution. The inputs for the and Y - deflection may be balanced or single ended, bipolar or offset, and positive- or negative-going without any

to

modification

The VR14 and VR17 come in several configurations, listed in Table 1-1.

Designation

VR14-0

VR14-A Rack 230 V VR14-B VR14-C Table VR14-D Table VR14-E Table VR14-LC Table 115 V VR14-LD VR17-LC VR17-LD Table

the VR14/VR17.

1-1

Table

VR14 and VR17 Configurations

Mounting Power Light Pen

Rack

Table Table

inches diagonal).

115V

100V 115V 230 V 100V

230 V 115

V

230V

of

fully solid

Option

No No No No No No Yes Yes Yes Yes

X-

GENERAL

this variation, intensity pulses may be time multiplexed or

by

gated timeshared

The VR14/VR17 versions with the light pen option (VR14-LC, VR14-LD, VR17-LC, VR17-LD) do not have this timesharing capability nor channel selectivity. They contain a W684 Intensity the W682, and a G840 Light Pen Amplifier in place G838. The protection circuitry

1.2 VR14/VR17 specifications are

Physical:

Height Width Depth Weight Viewable Area 6-3/4 in.

VR14 and VR17 Spot Size:

a separate input to allow the screen to be

by

two inputs.

G840 circuit board, however, contains the fault

SPECIFICATIONS

10-1/2 in. 19 in. (483 mm) 17 in. (432 mm) 75 lb (34 kg)

(171.45

INFORMATION

Control Circuit Board in place

of

the G838 board.

as

follows:

VR14

(267

mm)

15 21-1/2 in. 27 in. (686 mm) 85 lb (39 kg)

X 9 in. 8-1/4 in. X

X 228.6 mm) (210 X 280 mm)

VR17

in. (381 mm)

(546

11

< 20 mils inside the usable screen area at a brightness

30

fL

Jitter:

<

±1

/2

spot diameter

of

mm)

in.

of

the

of

The VR14 versions without the light pen option contain a W682 Intensity Protection CHANNEL switch which operates with the W682 board. In

Control Circuit Board and a G838 Fault

Circuit Board,

as

well

as

a front panel

Repeatability:

< ± 1 spot diameter

(Repeatability tion

1-1

is

of

any given spot)

the deviation from the nominal loca-

Gain Change:

flXed

From a change for each

point on the screen, less than ±0.3% gain

±1

Temperature Range:

0°

to

50° C (operating)

Relative Humidity:

10%

to

90% (noncondensing)

Brightness:

~

30 fL for

VRI4, ~ 25

shrinking raster technique

% line voltage variation

fL for

VRI7;

measured using a

4. Common mode rejection ratio,

5. Maximum operating input, ating input

is

the sum

of

40

dB

±6

V.

(Maximum oper-

the common mode input

and the differential input.)

6. Input offset not to exceed ±1/2 peak-to-peak input signal.

7. Maximum nonoperating input,

c.

Full screen deflection and settling time to within spot diameter, ~ 18

}J.S.

±50 V

±1

Linearity:

Maximum deviation

any straight line

is ~ 1 %

of line length, measured perpendicular to a best-fit straight line.

Deflection Method:

Magnetic

(70° diagonal deflection angle)

Focus Method:

Electros ta tic

High Voltage:

10.5 kV dc nominal (voltage proportional to input line

voltage). Supply

is

self-contained and equipped with a

bleeder resistor.

Shielding:

is

CRT

fully enclosed in a magnetic shield.

Overload Protection:

Unit

is

protected against fan failure or air blockage by

thermal cutouts. Power supply and amplifiers

is

limited. Phosphor protection

provided against fault

are

conditions.

Deflection Amplifier

a.

Deflection amplifiers are dc coupled and are capable of

sustaining a full screen

ac

or dc deflection

environmental extremes.

b. Input Specifications:

1.

Inputs are differential.

2. Differential input impedance,S

3. Input sensitivity,

500 mY/inch maximum (200

kQ

minimum.

m V linch with resistor change)

of

the

current

at

d. Small signal settling time to within 1/2 spot diameter,

~1

}J.s

for a 0.1 inch deflection

e.

Small signal linear

f.

Velocity error coefficient, 500

slew

rate, ~ 0.4 inch/l

}J.S

ns

maximum (average

ramp delay between input and output)

Z-Axis (on

a.

VR14 without Light Pen Option) Z-Input - A negative transition from ~ +2.4 not exceeding negative than

+8

V, to ~ +0.8 V, but not more

-4

V, in ~ 20 ns, causes an unblanking

pulse at the CRT cathode from approximately +62

to

ground with a duration

of ~ 200

ns

at the 50 percent points. Delay between the 50 percent point of

the negative input transition

point

of

the output pulse

to

the 50 percent

is

less

than 100 ns. Driver

must sink 4 rnA.

b. Z-Direct - A positive-going pulse not exceeding

but at least 45 V in height and not exceeding but

at least 1

viewable intensity. This signal

}J.S

in duration, unblanks the CRT

is

ac

coupled to the

CRT grid.

c."

Channel Select - With the Channel Select Switch in

Channell

the +2.4

V, but not exceeding circuit. negative than

position, a positive level

A level

of

less

-4

V, disables the circuit. With the

of

greater than

+8

V, enables the Z-input

than +0.8 V, but not more

switch in the Channel 2 position, a positive level disables the Z-circuit; a negative level enables it. Placing the switch in the Channel 1

& 2 position

disables this input.

V,

65

10

but

}J.S,

to

V

V,

a

1-2

Z-Axis [on VR14/VR17 with Light Pen Option (VR14L and VR17L)]

a.

Z-Input - This low, it un blanks the voltage to change from approximately +62 ground. The CRT will remain unblanked the Z-input

b. Intensity

the brightness control, generate a voltage

80 V to 0 V on the CRT grid 1,

brightness. The combination signals asserts one which in turn

is

a TTL logic signal. When a TTL

CRT by causing the cathode

is

at a logic low.

0,

1, 2 - These three signals, together

to

determine image

of

the three intensity

of

eight possible analog voltages,

is

ANDed with the output

as

long

of

V

with"

from

the

to as

brightness control to generate a grid voltage in the to - 80 V range. Thus, there are eight intensity levels at each

of

the infinite positions

of

the brightness

control.

Power

a.

All

power supplies necessary for operation

of

the unit

are self-contained.

b. Input Requirements

Voltage: (Selectable by tap changes)

100 V ± 115 V ± 230 V ±

Frequency Power Current -

10% 10% 10%

::;:;;;;

500 W

::;:;;;;

50-60

5 A

Hz

Type - Single Phase

The W682 accepts a gating input that allows the intensity pulse

to

be time-multiplexed between two input sources. The G838 Fault circuit in the event phosphor screen from burning,

Protection Board disables the intensity

of

a ±22 V failure. This prevents the

as

there would be no

deflection under these conditions.

Line power

is

passed through a fuse, an on-off switch, and

then through one normally closed thermal cutout switch.

is

The switch in the event

heat sink,

located

of a fan

VRI4/VRI7

cools down. The line power

on

the +22 V regulator heat sink, and

failure or excessive temperature on the

input power will be shut off until

is

then connected to the power transformer, the high voltage power supply, and the fans. The high voltage supply converts the input line voltage to

0

10.5 kV

that

is

connected to the CRT anode. The power transformer has three basic secondaries: a 6.3 ment, a 70/150 for CRT electrodes, and a 72 V center

Vac

is

tapped for deflection. The 72 to provide ±43

Vdc unregulated. This ±43 Vdc

rectified and filtered

with circuits on the G836 board, along with four power transistors on the regulator heat sink assembly. The regulated output deflection amplifiers. The on the G836 to generate

-80

Vdc

is tied to the grid. One side connected can

to

adjust the maximum brightness range potentiometer. The and also

to G836 board. The wiper directly to the focus electrode on the

is

±22 Vdc and

70/150

is

distributed to the

ac

is

rectified and filtered

±80 V dc and +400 V dc. The

used for the brightness potentiometer which

of

the brightness control

another potentiometer on the G836 which

of

+400 Vdc

one side

of

is

supplied directly to grid 2

the focus potentiometer on the

of

the focus potentiometer goes

CRT.

V for fila-

is

regulated

the brightness

it

is is

1.3

BLOCK

Figure I-I

DIAGRAM DESCRIPTION

is

the functional block diagram

of

the VR14 without the light pen option. The X-and Y - position signals are connected to their respective A225 Deflection Ampli-

Circuit Boards. The A225s boost the input signal to a

fier

level sufficient

to

drive the power transistors, while also

providing gain and position controls. In turn, the power

transistors drive

the

deflection yoke that positions the electron beam on the screen. The yoke currents are then passed through a

currents back into voltages that are used

0.5 n resistor that converts the yoke

as

feedback for

each A225 deflection amplifier. This feedback allows the

of

A225 to produce an exact current replica in the yoke

the

input signals.

The intensity input that converts this input to a cathode. The cathode pulse

is

applied to the W682 circuit board

60 V pulse which drives the

is

negative going; this pulse

turns on the electron beam, creating a spot on the screen.

Figure i.e.,

1-2

is

a block diagram

VRI4/VRI7

of

the

VRI4L

and VRI7L,

with the light pen option. Note that the G840 Light Pen Amplifier replaces the G838 Fault Protection Circuit Board. The G840 contains the G838 circuitry as

well

as

an amplifier to detect and shape from the light pen. The output brought out

of

the

VRI4L/VRI7L

of

the light pen amplifier

through pin

pdse

24-contact amphenol connector (117) at the rear display monitor.

Note that

in

the

VRI4L

and

VRI7L,

the W684 intensity

control replaces the W682. The W684 allows an intensity

is

pulse to the cathode whose duration

equal to that Z intensify signal. The W684 circuitry also modifies the grid I bias voltage, thereby allowing eight intensity levels for a

of

particular setting

All

other circuits represented in Figure

those represented in Figure

the front panel brightness control.

1-2

are

identical

I-I.

1-3

outputs

19

of

is the the

the

to

115~o---l

VAC

INPUT

»-----------,

l I

FROM

THERMAL

CUTOUT

115VAC~

115VAC

POWER

TRANSFORMER

115 VAC

UNIT

POWER

RECTIFIERS

+ FILTER

CAP.

CHANNEL

1>---------------~~~----~

CHANNEL

2»--------~o

Z INTENSITY

>--------------

....

+22V

-22V

POWER

SUPPLY a

REGULATOR

BOARD

G836

+80V

X FEEDBACK

X

INPUT

>-------------t

THERMAL CUTOUT

~-------+

+22V

~------+

-22V

~------+

FOCUS

X

POWER

TRANSISTOR

y

Y INPUT

>---------1"

~~~tl~~~~N

~_---I"

PO~ER

A225

RANSISTOR

115VAC

HIGH

VOLTAGE

POWER

SUPPLY

10.500VDC

ANODE

0.5

J'l.

.?"'I---~+-~-

CURRENT

SAMPLE

+20V

-20V

~t

GAIN Y

IpOSITIONI

r;;;l---<

115

L.:.::.J----<

VAC

0.5.n. CURRENT SAMPLE

Y

FEEDBACK

CP-0758

Figure

1-1

Block Diagram

ofVR14

Without Light Pen Option

115~~

VAC

I

FROM

THERMAL

CUTOUT

INPUT

)>-------------,

1

115VAC

POWER

TRANSFORMER

115 VAC

UNIT

POWER

RECTIFIERS

+ FILTER

CAP.

INTENSITY

0'>--------------.....,

l~tt~~IH

1

>-

__________

----I~L---__,

POWER

SUPPLY a

REGULATOR

BOARD

GS36

THERMAL CUTOUT

~------+

+22V

~------+

-22V

r-------.

FOCUS

~------++400V

~------+

+SOV

~--------+

-SOY

r--~-'---......L.----1

DEFLECTION

YOKE

115VAC

HIGH

VOLTAGE

POWER SUPPLY

10,500VDC

ANODE

INTENSITY

OUT

C>-------------~

~--__=_------:---==::;j~~-~.i:~==~

LIGHT

PEN

INPUT

+22V

-22V

LIGHT

PEN

PULSE

-x

INPUT

>------~

+YINPUT>------~~

-Y

INPUT>----------~

Y

FEEDBACK

Figure

1-2

VR14L/VR17L Block Diagram

0.5.n.

,2>----+--iI-+-

CURRENT

X

POWER

TRANSISTOR

Y

POWER

RANSISTOR

+22V

-22V

r;;:;l---<

115

L..::J----<

VAC

SAMPLE

0.5

J),

CURRENT SAMPLE

cp-

0760

CHAPTER

2

OPERATION

2.1 INSTALLATION The VR14 by

10-1/2 inch

is

shipped either

(l0-7/16

as

a standard RETMA 19 inch

inch) rack-mounted unit or

as table-top model (without chassis slides) with its own decorator cover. 'The VR17 comes only in a table-top model. The

VR14/VR17

frequency between

is

however, VR14/VR17 100

V). The input interconnections

specified

(O,C

VR14/VRI7

line voltages simply

on

is

can operate from a power line

47

and 63 Hz. The by

a letter designation after the

115 V; A,D

input

is

230 V; and B,E

can operate with any

by

changing

TB 1 and TB2 (Figure

the

2-1

line voltage,

of

the three

jumpers and

and drawing

D-CS-7007084-0-1 ).

is

Equipment cooling installation requirement. Fans draw air from

the

unit; therefore,

provided below

keeps the

bottom rack-mounted unit, below the

VR14, VR14 fans (a screen

is

1 inch

not),

requirements apply,

the most important VR14/VR17

the

bottom

at

the

bottom

least 1 inch

of

chassis.

free air space must be

The

table-top model

1 inch above the table surface. In the

if

equipment

as

long

as

is

acceptable; a solid plate closer than

is

mounted immediately

there

is

open area under the

proper cooling can occur. The same

on

the rack-mounted unit,

to

the area

of

immediately above the unit. The table-top model has a solid top

cover. The cooling air exits from Therefore, at least 2 inches immediately behind VRI4/VRI7 that

would cut

flush against a wall or solid vertical surface

off

the

air circulation.)

of

free space must be provided

unit. (Do

the

rear

not

of

the

unit.

push the

NOTE

Before applying power

that

the

ensure

position potentiometers are set

to

the

VR14/VR17,

for the particular input signals being used. Because input

signals,

driven

the

into

saturation far

universal nature

deflection amplifiers may be

off

screen

of

allowable

by

position

of

the

settings. Leaving the deflection amplifiers saturated way off screen continuously may cause damage.

See Paragraph 2.S and Table 2-2 for

proper settings.

115 Vac

a

is

Interchange

with

Orange Red

(from

Transformer)

2.2

FRONT PANEL CONTROLS

TBl

1

(2)

3

4

5

@

TBl

Figure

~

__

~ju_m~p_er

~

__

~ju_m~p_er

230 Vac

jum

100 Vac

jumper

2-1

Input

per

The on/off, brightness control, and

(not

control

applicable to

the front panel. The

the

VRI4/VRI7

when the

VRI4L/VRI7L)

on/off

switch turns on input power

knob the maximum counterclockwise knob clockwise also increases the brightness

TB2

____

1

~~

3

4

5

~@

TB2

1

~

3

4

5

®

TB2

4 5

®

Power Jumper

the

channel select are located

is

rotated clockwise from

off

position. Turning the

of

Interchange

White

with

Gray

(from

Transformer)

on

to

the dis-

2-1

played information. A delay before information appears filament warms up. In an operating system, mended that power be left on the display even when not

in continuous use

do

not

occur.

so

The channel select switch

of

about

30

seconds occurs

on

the

screen while the CRT

it

that

the

filament warmup delays

on

VR14s without the light pen

is

recom-

it

option works in conjunction with the channel select signal

not

applied at the rear connector. When channel feature,

the

select switch should be in the 1 & 2

position. When using the dual-channel system, points

using the dual-

on

the

screen will be intensified from Z-intensity inputs only when

is

the channel select signal at the rear connector

is

in

the

the channel select switch

input

channel select is

at 1, intensification ceases. On the

signal goes low while the select switch

Channell

other

Channel 2 position works in the opposite manner.

input

signal

is

channel select

low and the select switch

high and

position.

hand, the

If

is

the

at

2, Z-intensification signals will intensify on the screen.

if

Thus,

a group

from another group, separation can be achieved

of

information points

is

to

be separated

by

having

group 1 intensification pulses occur only when the Z-select

is

high, and group 2 intensification pulses occur only

line

the

when overrides

Z-select line

the

cation pulse

select of

is

low. Channel select position 1 & 2

input

signal and displays every intensifi-

both

channels at once. To observe only

Channel 1 information, select Channel 1 and all Channel 2

signals are locked out. By selecting

Channel 2, only Channel

2 signals are displayed.

2.3 REAR PANEL

CONNECTORS The rear panel has an Amphenol 14·contact connector (JI8)

and an Amphenol 24-contact connector

2-1

and 2-2 list rear connector pin assignments.

(JI

7). Tables

of

input

variety centered on the particular

is

rarely have to be adjusted. Gross positioning

input

excessive gain deflecting

signals and allow offset inputs

CRT screen. Once initially adjusted for the

Signals

used, the gain and position controls

off

the

extremities

should be avoided, since the deflection amplifiers will go

if

into current limiting and may overheat

of

this condition any length

controls clockwise, increases

the

size. Turning

X and Y positions clockeise moves the

time. Turning the X and Y gain

the

allowed

gain or displayed image

displayed information right and up, respectively.

The focus and brightness preset adjustments are located at

top,

the

right central portion

power supply regulator circuit (G836)

the

top

recessed from the rear-most

of

range

the

of

front panel brightness control

of

the two. This potentiometer allows the

of

the

unit. They are

that

the unit. The brightness preset

any maximum brightness desired. Turning preset counterclockwise increases the maximum brightness

of

the

range set so panel knob,

front panel control. Generally, this control

that

at maximum brightness setting

the

displayed information does causing a degradation in resolution. The focus potentiometer is

is

in front

of

the

brightness preset. The adjustment

quite insensitive and requires several turns

focus.

The VR14L and potentiometer (R29), located accessible from

VR17L

the

top

also contain a contrast adjusting

on

the

W684 module.

of

the

VR14/VR17. This control used to extend or contract the brightness range display. initial adjustment

It

does

not

normally have

is

made

to

be changed after an

to

compensate for component

variations.

off of

the screen

is

somewhat

to

be limited

the

brightness

on not

to

go through

of

to

be

screen or

to

stay in

on

the

is

to

is

the front

"bloom"

It

is is

the CRT

2.4 INTERNAL CONTROLS

The

VR14/VRI7

ometers:

X position, X gain, Y position, Y gain, focus, and

internal adjustments include six potenti-

brightness preset. Access to the adjustments

the

removing

case cover (Figure 2-2).

The gain and position adjustments are located

of

left central portion

the VR14/VR17 (as viewed from the

front). The two forward potentiometers on the deflection

on

circuits are the horizontal gain on

the

right. The two rear potentiometers are the hori-

zontal position

on

the left, and the vertical position

the left, and vertical gain

right.

the

The gain adjustments allow modate a range

of

input signal amplitudes and expand or

VR14/VR17

contract the horizontal and vertical deflection to suit full screen requirements. The position controls accommodate a

is

gained by

on

the top,

to

accom-

on

the

2.5 INPUT

SIGNAL REQUIREMENTS

NOTE

The deflection amplifiers must

the

that of

time

Ensure

CRT beam

or

that

is

off

permanent damage may occur.

input

deflection signals fail

not

be driven so

screen for any length

safe, on-screen value.

The VR14/VR17 requires analog voltage inputs for

V-deflection, and a logic level change or pulse for intensify.

X-

The CRT deflection deflection inputs are differential

and V-inputs are identical. However, because the

is

a 3 X 4 rectangle, only

is

required for full vertical deflection. The

3/4

of

the horizontal

but

may be driven from

single-ended sources. When using single-ended sources, the

is

differential input loops and hum. By carrying

helpful in eliminating annoying ground

the

"local" common or ground

2-2

to

a

X-

and

Table

2-1

117 Rear Connector Pin Assignments

VR14

L/VRI7

L

11724-Pin

Destination

Signal Name

Function

Signal Name Function

Connector

Pin 1

A4L

Z-Select

High

input enables

Z-intensify

to

Intensity 2

Determines intensity level

occur

if

channel select switch on

1.

A

low input enables Z-intensify

to

occur

if

channel select switch on 2.

Pin 2

A4B

Not Used

Intensity 0 Determines intensity level

Pin 3

A4K

Not Used Intensity 1

Determines intensity level

Pin 4

A4J

Z-Input

When this input goes from high to low, Z-Input

When

this input

is

low, an intensify

an intensify pulse

is

generated. signal

is

applied to the CRT.

Pin 5 GND

Pin 6 GND

Pin 7

A2B

-X

Input One side

of

X~input

signal line -x Input One side

of

X-input signal line

Pin 8

A2E

+X

Input

Other side

of

X input signal line +X Input Other side

of

X-input signal line

(ground for single ended input)

Pin 9

A2H

X-Signal

GND

X signal reference ground

X-Signal GND X signal reference ground

10

A3B

-Y

Input

One side

of

V-input signal line

-Y

Input

One side

of

Y -input signal line

11

A3E

+Y

Input

Other side

of

Y input signal

line

+Y Input Other side

of

Y input signal line

(ground for single ended input) (ground for single ended input)

Pin 12

A3H

V-Signal

GND

Y signal reference ground V-Signal GND Y signal reference ground

13

A4D

Z-Direct

Input signal that directly modulates

Not Used

CRT grid (ac coupled)

14

N/C

Table

2-1

(Cont)

J1

7 Rear Connector Pin Assignments

VR14

VRI4L/VRI7L

J1724-Pin

Destination

Signal Name Function

Connector

15

JI8-Pin4

Not Used

Bell (Speaker) Used in

LK40 option

16

N/C

17

JI8-Pin

5

Not Used

+K.B

Signal Used in LK40 option

Pin 18

JI8-Pin

6

Not Used

-

K.B

Signal

Used in LK40 option

19

AIH

Not Used Light Pen Out

Amplified light pen pulses

Pin 20

JI8-Pin

12

Not Used

+5

VIN

Used in LK40 option

21

N/C

22

JI8-Pin

8

+22 V +22 V

is

available

if

JI8-Pin

8

is

+22V

+22 V

is

available

if

JI8-Pin 8 is

jumpered

to

JI8

1.

jumpered to J 18 pin 1.

Pin 23

JI8-Pin

10

-22

V

- 22 V

is

available

if

JI8

pin 10

is

- 22 V

is

available

if

JI8

lOis

jumpered

to

JI8

pin 3.

jumpered

to

JI8

pin 3.

Pin 24

JI8-Pin9

GND

JI8

pin 9 must be jumpered to

JI8

GND

JI8

pin 9 must be jumpered

to

JI8

2.

pin 2.

Jl8

14-Pin Connector

Jl8

Rear Connector Pin Assignments

Destination

Table 2-2

Signal Name Function

Pin 1

Pin 2

+22 V Regulated

GND

Pin 3 - 22 V Regulated

Pin 4 117

Pin 5 117 Pin

Pin 6 117 Pin

Pin 7

8 117 Pin 22

Pin 9

N/C

117

15

17

18

Pin 23

Pin 10 117 Pin 24

11

N/C

V

+22

GND

-22

V

Bell

(Speaker) Used with LK40 option

+KB

Signal Used with LK40 option

-KB

Signal Used with LK40 option

For

VRI4/VRI7

For

VRI4/VRI7

For VR14/VR17 options

Not Used

+22 V

GND

-22V

Jumpered from J18 pin 1 to 118 pin

P18

8 by

Jumpered from 118 pin 2 to 118 pin

P18

9 by

Jumpered from 118 pin 3 to 118 pin

10 by P18

options

Pin 12 117 Pin 20

13

Pin 14

along with the deflection signal from where it

a quasi-differential signal

is

nating this ground at the

as

if

it

ground

were one side other side being the deflection signal itself). VRI4/VRI7 own ground and not the

uses

the deflection signal with respect to its

VRI4/VRI7

GND

-22

V

is

generated. Instead

VRI4/VRI7

of

a differential signal (the

chassis,

ground, which, most

generated,

of

termi-

use

the

The,

likely, is different and could cause picture ripple and hum.

If

a separate ground

Signal

is applied to one side

remaining differential input

of

impedance

the driving signal or,

is

not available, the single deflection

of

the differential input. The

is

terminated with the source

if

this

is

low, the input

simply grounded (signal ground not chassis ground). (Signal

ground

is

pin 9 and pin

12" X-and Y

-signal

ground,

+5V

GND

-22

V Provides

respectively.) Never reference - always or differential inputs, tie each side

Provides

use

+5

V to LK40 option

GND

to

LK40 option

-22

V to LK40 option

chassis ground for X-and V-input

Signal

ground.

When

of

the twisted-pair shielded cable to the two inputs and the shield to the signal ground. The importance

of

using signal ground cannot be overstated; most noise and washing displays are a result indiscriminate grounding.

The minimum voltage

peak-to-peak and 1.7 V for Y when A225 are 3.3 and R2 are normally 10

is

input sensitivity

kn

is

minimum for maximum sensitivity

Signal

for full X-deflection

Rl

and R2 on the

(Figure 3-1). For larger input signals,

kn.

With 10

kn,

0.5 V linch. The input impedance (RI

and R2: 3.3

using balanced

of

is

2 V

Rl

the maximum

is 5 kn

kn)

.2-5

POSITION

HORIZONTAL

VERTICAL

---r

.........

5481-1

Figure

2-2

Locations

and 20 kQ minimum for long cables (more than not be possible unless the cables

(less.

impedance impedance

than 100 Q) since the VR14/VR17 input

is

too high for this application.

Input signals larger than 2 with the gain controls and

Rl

and R2 =

10

kQ.

When

driving

30 feet), high-speed deflection may

are

terminated in a low

V may be used by attenuating

Rl

and R2 on the X-and Y -deflection circuit boards. However, the potentiometers become much too sensitive for input signals greater than

10 V peak-to-peak and

Rl

and R2 should

be

increased to

provide pre-attenuation for these larger input signals. The

as

±5

input signals may be bipolar such

V or unipolar such

of

Internal Controls

as

0 V to

+5

V or 0 V to - 5

V.

The position potentiometer allows the deflection to be offset plus or minus half a screen; thus, a unipolar signal may be completely centered on the screen.

Offsets more than half

of

the full-scale inputs

cannot be handled. In other words, if the full-scale

is

deflection

offset from 0 V by more than half its 'full scale

value, centering on the screen cannot be accomplished. A

V peak-to-peak deflection signal, for example, may not

3

offset from 0 by more than ±1.5 or 0 V that

to

+3

goes

from + 1 V to

V are

all

acceptable, but a deflection input

shifted down a minimum

V.

So

±1.5 V, 0 V

+4

V cannot be used until it

of 1 V.

Table

2-3

summarizes the

control settings for various inputs.

2-6

to

-3

be

V

is

2-3

Table

Control Settings

Input Deflection

±2

Vto

5 V

0,0 = center +2 V to

and

o V

0,0 = upper right screen

o V to - 2 V

0,0 = lower left

The Z-intensify input requirement tion from high to low. In VR14s using a W682 Intensity Control, this triggers the intensity circuit 300 ns intensify pulse. In VR14Ls and VR17Ls, which the W684 Intensity Control, the intensify circuit gered, and remains active, until Z-intensify

+5 V is

to

right

to

+2 V to

The intensify signal must be delayed from the

X-

length settle the electron beam to its required position. Failure to do that are located incorrectly on the screen. Also, at

least a 500 to electron beam to move to its next location. Not giving enough time to intensify a dot after the deflection since the deflection amplifier ging" the dot to the new position. The amount of V-position information VRI4/VRI7 requested depends upon how large a position

change the dot has to be to its final ideal position. Full-scale deflection changes, such

far right or corner to corner, require a 20

waiting period for the dot

0.01 inch

be tolerated, tion changes require much change can be settled in

up

+5

V

to

- 5 V

and V-position signal for an appropriate

of

time to allow the deflection coil to

intensify a dot before commanding the

is

delay required from the time new X-and

is

requested and how perfectly settled

of

its final value.

With no inputs, set X-and position potentiometers to get

o

(for Y).

With no inputs, set A02-A, A03-A with V-position potentiometers.

With no inputs, set +2.2 V A02-A, A03-A with

Y -position potentiometers.

NOTE

so

ns

waiting period must be allowed

settled

18

will

and

the

J.ls

may be used. Small deflec-

Position Setting

Vat

A02-A (for X) and A03-A

is

simply a TTL transi-

to

goes

high.

displays smeared dots

also smear the dot,

will

start "drag-

is

presented to the

intensify pulse

as

far left to

to

settle to within

If

larger errors can

less

time. A

than 1

J.lS.

0.1

If

there

Y-

-2.2

V @

X-

and

X-

and

generate a

use

is

trig-

is

J.ls

inch

is

no way for the circuits driving the VRI4/VRI7 changes from large ones, each change must be

assumed

worst-case delay. Also, driving the display have

generated while changing values), proportionately longer delays are required since the

deflection amplifiers have to recover from the "gliches. "

The Z-direct input (applicable only pen option) allows direct modulation Positive-going signals increase brightness. This input direct coupled; therefore, dc brightness information cannot

@

be

used. The

Z-direct may be used with or without the Z-intensify input.

If

Z-direct brightness subtracting at the CRT grid. This pulsing the Z-direct with a pulse Z-intensify.

Z-direct pulse, the dot

When

vector intensity control or any other non-point plotting application) the signal the CRT cutoff. A typical direct signal

10 V of 40 V pedestal; the reside below cutoff.

The Z-select input (applicable only to VR14s without light pen option) works in conjunction with the front panel channel select switch. The Z-select allows the Z-intensify pulse to be gated or time multiplexed. select switch

no

effect the 1 position, Z-intensification occurs only when Z-select input Z-intensification occurs only when Z-select low. Thus, displayed, by placing Z-select at a high only during

1 intensification times, and low only during Channel 2

intensification times, both curves the channel select switch when is

selected.

In the VR14L and VR17L, brightness level three input signals [Intensity panel brightness control. These input signals combine in the

W684

of

1

of

using Z-direct without the Z-intensify (such

actual brightness information riding on top

on

is

a TTL high.

if

Channel 1

module

the CRT, establishing a particular brightness level.

to distinguish small position

to

be large and thus requires the

if

the

D/

A converters

"gliches" (error spikes

to

VR14s without light

of

RC

time constant

is

used with Z-intensify, it can alter the

the normal intensify pulse by adding or

By

varying the amplitude and polarity

40

V pedestal ensures that the CRT will

is

on the 1 & 2 position, Z-select inputs have

the VR14.

When

two separate pieces

is

selected, and Channel 2 when Channel 2

to

generate a voltage which

is

approximately

is

accomplished by

of

equal duration with the

will

be

of

a different brightness.

must be large enough to overcome

will

When

the channel select switch

of

information are to be

will

be displayed when

is

at 1 & 2, and only Channel 1

(2:0)],

as

well

is

the brightness.

is

not

30

ms.

The

of

the

as

for

have 5 V to

of

the channel

is

at 2,

is

held at a TTL

Channel

is

a function

as

the front

applied to grid

a

in

of

2-7

CHAPTER

3

3.1

X-

AND

Y-DEFLECTION

The X-

only one axis will

consists and applied input

even

single-ended source being a special case where one side minimum

R3,

R3

ended gain to C6, which and

frequency gain established ratios. A ±6 V

±22 Zener diodes

CI

filters for the ±6

noise

possibility

of

deflection amplifier;

preamplifier.

The

amplifier, i.e.,

current

input.

current

the

to

voltage across this resistor

flowing in

voltage with

and

Y -deflection circuits are identical; therefore,

be

of

the A22S circuit

a deflection

to

pins E

signal

if

the

input

the

gain

is

amplified

by

amplifier E1.

is

established

RS.

The

bandwidth

act

CI4,

which act

V. This

and

C3, and C2

at

each operational amplifier, thus avoiding

of

EI

is

conducted

amplifier

1800 out

Because the

must

feedback compare volts

voltage

with a O.S

the

yoke

and B on

is

handled as a differential

input

is driven

is

grounded).

impedance and form an

potentiometer.

and

converted from balanced

by

the resistor ratios

of

internally

at

is

generated for

is

done

by

DS

and D6.

and

V

to

parasitic oscillation.

to

RII,

EI

is

essentially an inverting voltage-to-current

an

input of

phase or inverted with respect

input

be converted

n resistor

yoke;

thus, the amplifier compares the

the

yoke

dropping resistors

CIRCUITS

described.

(Figure 3-1).

from

EI

is an inverting amplifier whose

the

on

the

high frequency

by

C4 are local high frequency bypass

reduce any high frequency signal

which

serves more

voltage

is a voltage, however,

back

with

is

current

The

board,

two

the

A22S circuit board.

a single-ended source

RI

and

The voltage developed across

amplifier

integrated circuit, and

the

R7

both

The is

the

as

is

converted

into

a voltage in order

volts. Current

in

series

an

exact replica

to

ensure

deflection circuit

power

transistors,

The

input

signal is

The

or

balanced signal,

(the

of

a balanced

R2

establish the

attenuator

of

R7

to

is

tailored

to

roll

to

R4

and

EI

and E2 from the

RI8

single-ended

input

a signal conditioner-

to

with

the yoke. The of

that

to

R4

and

by

off

the low

R6

and

RI9

to

the

an

the

is

converted

the

input

with

single-

CS

and

CI3

to

and

output

actual

output

to

output

that

current

input

yoke

R6

RS

the

this

THEORY

current compares voltage

Because is changes in through resistor changes. Therefore,

voltage appears

ly respond in a manner pin 10

E2.

output continuous null occur is

exact equal input but

In

voltage can be determined

example,

flow

is 1 V,

10

because

current

if

RIO/R31

negative.

feedback voltage

originates

therefore,

through

excessive

(explained later) would probably be called

limit

is

an exact replica the

at

R3I,

the

amplifier has voltage gain, only a small voltage

needed between pins 10 and 9

the

RI3,

that

minimizes offsets in E2 due to temperature

to

zero; thus, a null

If

a variable voltage is present

(or

yoke

if

instantaneously

and

to

Ril.

opposite polarity replica

absolute numbers, the actual

if

+ 1 V

through

10

of

the

RII.

of

E2

to

so 1 rnA flows. This

E2

because,

the

input

must

flow through RIO

feedback voltage is a negative value, because

is

tied

In

fact,

from

-3.2

the

yoke. This,

amount

output

OF

input

voltage

RIO.

output.

which is strictly

at

10

current) will vary in such a

is

achieved

opposite changes

Therefore, the

is

applied

This occurs because the amplifier forces

0 V; thus, one side

if

it

of

E2

to

if

1 rnA flows through RIO

must

the 0.5 n resistor in series

V divided

of

transistors.

OPERATION

of

the

input

at

RII

of

Pin 9

of

E2

is

referenced

an

impedance balancing

9 is essentially grounded.

of

E2,

the

output

that

tends

to

reduce the voltage

is

always achieved

at

the

at

10.

The

the

yoke to

those occurring

yoke

current

of

the

input

yoke

current

by

comparing resistor ratios.

to

the

input

of

RII

current

did, pin 10

looks like a high impedance.

10

which

be

3.2

by

of

course,

voltage, and

does

would

and

R31.

is

0 V; so pin A

V and negative. The

O.S

n current is flowing

is

-6.4

current

position signal.

with the feedback

E2

to

cause large

to

will immediate-

at

input

of

manner

only way this can

current

voltage.

of

not

undergoes

will be an exact

versus

RII,

1 rnA will

is

0 V, the

flow

rise in voltage

This occurs only

and

with

A which

limit circuits

into

E2

ground

If

any

at

10

of

RII,

the

that

at

the

input

For

other

into

The

must

be

R3I,

the

-3.2

V

the yoke;

is

an

action

to

a

3-1

The remaining transistors

to

from E2 transistors Ql

through its base resistor R14. poses: a stage necessary

a sufficient drive level to operate the power

on

the large heat sink. The

of

inversion and a level shifter. Inversion

to

get the final negative feedback. Level shifting its base voltage; E2 cannot do this alone. The no voltage gain

but voltage and current gain and voltage

is

first generated. Q2

on

the A225 boost the current

output

Ql

output

in the proper polarity for is

required

of

E2 drives

serves two pur-

to

drive Q2 at

Ql

stage has

has current gain. Q2, however, has

is

where the true

is

a "grounded" emitter

output

amplifier where, in this case, the emitter, although tied to

V, can be considered "grounded" and the col1ector

+22

is

not

tied

to

- 22 V

but,

resistor R23

-44

V. Q2 has the capability

almost a full ±22

V. This large swing yoke, which must swing The reason for this

The collector

wi1l

of

Q2 drives Q3 and Q4 which are emitter

as

dose

be explained later.

for analysis, tied

of

swinging its collector

is

necessary for the

as

possible to the ±22

followers for the positive and negative outputs. output

however, Q3 and Q4 are

impedance

is

necessary, emitter followers are used;

not

capable

of

handling

Since a low

the

to

V.

output

power necessary since each can only drive 0.5 A. A

is

bootstrap power stage

current capability

used to raise the emitter follower

to

the ±4 A required. This

is

accom-

plished with two power transistors on an external forced-air

cooled heat sink.

These external transistors are essentia11y and

Q4 emitter followers. Because the positive swing and

"slaved"

negative swing work in the same way, only the positive described. When the amplifier current in the yoke,

the

thus placing a positive voltage

is

required

circuit responds

on

the base

to

by

emitter responds in a similar manner; however,

to

the Q3

is

deliver positive

turning Q2 on,

of

Q3. Q3's

it

cannot

supply the necessary yoke current. Still, Q3 attempts to

deliver the necessary current. fol1ower, Q3's collector

the

base

of

the

2N4399 Power Transistor, Thus, when Q3

to

tries

deliver the

is

output current must flow into Q3's collector from the base

Unlike a normal emitter

not

tied

to

+20 V,

but

instead

to

current from its emitter, this very

of

the

2N4399 which will now turn on. Because the 2N4399's

is

collector supports

also tied

the

output primary source demands, the 2N4399 turns on harder, so does the 2N4399. does the 2N4399. Therefore, emitter follower (Q3)

to

the

output

(the

yoke)

current and, in fact, becomes the

of

output

current. Depending

is

completely slaved

the

output

but

the 2N4399 deHvers

to

If

Q3 shuts off, so

looks like

on

Q3.

it

If

it

a11

also

Q3's

Q3

is

an

the current and handles the necessary power dissipation requirement.

To minimize power consumption, the operate in Class

B;i.e.,

while positive current

output

negative current transistors should be turned on and vice versa. However, this approach creates problems

is

where the transition between positive and negative current

is

that

takes place. The reason not

shut

off

exactly where the other set takes over, instead shut "no

man's land" where neither the positive nor the negative

off

prematurely. This creates a dead zone or

one set

of

transistors does

transistors are on and control1able. The appearance on the CRT screen nonlinear compression occurs (usually near the center can be solved shut

off

opposite side's region. In

would transistors were

of

such a phenomenon

of

displayed information where

of

by

not

allowing the positive transistors

at zero,

not

but

rathe:r conduct somewhat

SOl

doing, the positive transistors

shut off, for example, until the negative

weB

turned on. Thus, the amplifier would

is

a bunching or

the screen). This problem

have control to cancel any nonlinearities that might occur.

is

This task influence

accomplished with R23,

is

R23 because Q4 bases which conduction region

al10w

of

the other.

it

places voltage between Q3 and

one to

R26,

R27. The major

be

on a little

If

R23 were 0, the dead

zone would be very abrupt, causing maximum distortion.

On the other hand,

conducts further and further

as

R23

is

increased, the transistor

into

the

opposite side's operating region. This creates two major problems. The power dissipation causes excessive heating stage and the extra current required overloads the power

of

R23

is

supply. The value

but

also

dissipation

output

The

V. This

±22

less

than

0.1 n

curr~nt

L 20 signal

capability

through at high speeds requires a

LlI/Llt).

V. That

To change 2 A through 20

is

to

a large current

to

at

is

why the A225

force the yoke current

to

the

yoke has

necessary beeause even though the yoke

at

dc, it has inductance; thus,

Position control in the A225

to

E2

another input

is

This

accomplished with R9. The position "signal"

exactly

chosen, therefore,

minimize the cross-over distortion.

the

but

capability

not

only has

also has

is

accomplished

the

way the signal comes in.

of

lot

of

J.LH

in 2

to

boost the

to

have good voltage

to

change quickly.

nothing more than an adjustable dc level (from R8) which,. through R9, adds or subtracts voltage from the actual signal. This allows the displayed information

on

up/down, left/right

the screen or, in the case input signals, allows the information to be centered screen.

would like

is

required, no

at

the

to

point

but

to

into

the

into

the

of

the

output

to

minimize

swinging a full

to

force

voltage (V =

J.LS

requires

input

by

adding

input

to

move

of

offset

on

the

it

is

3-2

150pF

TYPICAL

If

YOKE

RETURN

,r

R31"

I R10

A

2.2K

IK

NOT USED

R30

D

270

*Rl

E

10K

-'VVV-

R3

J

~

..

5K,

+

INPUT

SIGNAL

B

*R2

10K

PW GN

R V

D~

L H

SIGNA

GND

Dl

.

I

~2

t

CW

03

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R5

IK

1/8W,I%MF

R6

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4.64

1/8W

1% MF

R9

C13

R8

4.7K

If

5K

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4.64

1/8W

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Rll

C5

IK

~

1/4W

5%

8

2

10

6

El

5

MC1520G

R32

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7

3

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R18

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R28

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T ---._+_2::..2::..V_--,,---

___

-7

+

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U

S

R

---'-~--I--1

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p

L

M

L_

K

-22V

7007ci2J

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0.1

I

~-.J

-22V

UNLESS OTHERWISE INDICATED

,..--

I I I

I

L

ALL

CAPACITORS ARE

10pF,

100V.

5%

ALL

DIODES ARE

0664

0--0=

JUMPERS

*FOR

THE

A-225-YA

VARIATION,

RI 8

R2 ARE

3.3K.

1/4W,

5%

FOR

I

NPUT SIGNALS LESS THAN 5V P-P.

NOTE:

Tnis

schematic

may

not

reflect most-recent

engineering changes.

-....,

YOKE ASSY I

7007088

I

_-.J

TO

A YOKE RETURN

0.5 25W 1%

TO

PIN H SIGNAL GND

CP-O?62

Figure

3·1

X and Y Deflection Circuit

3·3

The remammg component on compensation which allows required bandwidth

without

the

A22S

is

frequency

the

amplifier to operate over its

oscillation. Because the ampli-

fier must operate from dc to beyond 1 MHz, the voltage

must be reduced continuously at higher and higher

gain

If

frequencies.

this were between input and output R12,

to

be in phase with

R3,

R32,

C16,

output

CIS,

not

done, excessive phase shift

(from feedback) could cause the

the

input

and.

thus oscillate.

and

Cll

perform the required gain reduction functions. R12 reduces the open-loop gain of

E2 at all frequencies. C

frequencies and

is bandwidth. The yoke itself represents a major roll the

amplifier, and its high frequency characteristics dominate the stability the

yoke enhances the high frequency settling character-

of

istics

the yoke.

The power

by

limited the

the +22 V and

deflection amplifiers are driven way

of

output

power supply limits the maximum current

is

condition fuse or

allowed to exist, eventually either the +22 V

the

- 22 V fuse will blow, rendering the circuit safe

11

reduces the gain

of

major significance

the amplifier. An

of

to

RC

network across

stage (2NS302 and 2N4399)

-22

V power supply regulators.

off to

11

Q2 at high

the overall

off

for

is

current

If

screen, the

A.

If

this

from such overloads.

output

-22 Rl

the

voltage will be compared. The reference for the

V regulator

and establishing +6.2 V across

dynamic resistance

is

made with the +12 Vdc passing through

01.

Cl

across

of

the reference

by frequency fluctuations. The reference voltage R2,

which ties

amplifier

The feedback from the

is

also applied

R3 of

the circuit E1. Therefore, because stable,

the changes for any reason, El

then returns the null. increases, causing the

output

lated disturbed and that

the null could be maintained. On

heavy load occurred

-43 V to would act in a way enough

to

the summing point (pin

El.

output

to

the summing point

is

that

a null will be maintained at pin 2

the

only variable

is

the

forces the

For

output

example,

-43 V to

starts

to

climb. The null would

El

would shut

on

drop,

the

null would again be disturbed and

that

to

return to its proper level, the level

regulated voltage through

voltage

the

output.

null

is

disturbed at pin 2

to

change in a manner that

if

the

increase, the

the

output

the

-22

V regulator causing the

would turn on the

2)

of

on

R2 (reference)

Whenever the

input

down somewhat so

the

the null.

01

reduces

removing high

is

delivered to

of

operational

El.

The nature

output

of

line voltage

-22

V regu-

then

other

hand,

output

that

maintains

of

is

El;

be

if

El

hard

a

3.2

PLUS AND MINUS

LOW

VOLTAGE REGULATED SUPPLY The

input

line voltage

to

transformer

approximately

identical secondary windings

is

stepped down in the power

36

Vrms. There are two

to

deliver these

36

V. Both windings are connected in series, making a 72 V centertapped Winding. becomes approximately tap,

the

86 Vdc split evenly with respect +43 V and a filter capacitor finishes the task

Using full wave bridge rectification,

86

Vdc. By grounding the center

to

ground; thus, a

-43

V are available with respect

on

each ±43 V line smooths the ripple and

of

generating the raw, unregulated dc for

the ±22 V regulators. The regulators are contained

the

G836 circuit board (Figure 3-2) and to

the G836. Since the ±22 V regulators are symmetrical,

is

only the negative regulator

described. The ±43 V

heat sink adjacent

dropped by R33 and R34 and preregulated with

to

+12 Vdc and

the

voltages necessary

to

used

generate the reference voltages with which the

07

and

to

08

to

operate

-12 El

Vdc.

and

The E2;

the

ac

to

ground. A

on

the

05

and

06

±12 Vdc are

they are also

of

output

Q2,

output,

matter

R3 to

how

of

if

of

This regulating action takes place in a seconds. The actual

is

maintained

determined

output

voltage at which the null

by

the ratio the reference voltage. The mechanics the

output

can be traced stage by stage.

emitter follower, Q 1, to give the

to

fully

turn

drive capability through transistors

R12,

that

controls the base current

are external

on

to

the G836 board. The pass

transistors maintain a constant

the

supplied power from

raw dc source. Because

open-loop voltage gain, high frequency networks are used

to

roll

off

the gain

nonoscillatory operation. C2,

of

the

regulator

R5,

and

to

purpose.

The and tor

output

014.

current

is

power transistors are current limited

These diodes conduct whenever excessive collec-

is

demanded. In so doing, the diodes limit the base drive, thereby limiting the maximum fault current may flow.

of

micro-

will

be

R2

times

El

controls

El

drives an

E 1 sufficient

required.

Q2,

the series pass

since they are

of

the

high

ensure stable

C5

serve this

by

013

that

3-5

3.3 CRT ELECTRODE VOLTAGES The CRT requires the

fol1owing

electrode voltages: fila-

ment, cathode, grid 1, grid 2, focus, and anode.

The filament voltage of

the power transformer. The ±3.5 Vac windings are

is

derived from the ±3.5

Vac

windings

connected in series yielding 7 Vac. Due to resistance losses, approximately 6.3 Vac

The 70 Vrms winding bias voltages. The (Figure 3-2). Through winding generates a same winding, in like manner, generates C18, R37, and C19. The front panel brightness potentiometer. The other side

is

provided across the CRT fIlament.

is

used to provide cathode and grid 1

70 Vrms winding terminates on the G836

Dll,

C17, R36, and C16, this

-80

Vdc by half

wave

rectification. The

+80 Vdc from D12,

-80 V is

applied to one side

of of

the

the potentiometer returns to the brightness preset potentiometer

(G836-R38). voltage that can be made available to grid acts

as

a limiter

the brightness potentiometer

R38 setting determines the maximum

1,

and thereby

of

the maximum intensity. The wiper

is

connected

to

pin E

of

the W682/W684 circuit board. In VR14 versions where the W682

Intensity Control (Figure 3-3)

of

R9

to

by way

grid 1

of

the CRT.

is

used, pin E connects

directly to grid 2.

biased, the

CRT beam can never be turned on, regardless how much grid-to-cathode drive occurs. The 400 Vdc goes

to

one side

G836 board. The other side

-

80 V dc. The wiper CRT. Because focus may occur from unit to unit

-80

Vdc and +400 Vdc.

The anode

If

grid 2

i.s

not substantially positively

of

the focus potentiometer R35 on the

of

the potentiometer

goes

to the focus electrode on the

of

CRT manufacturing tolerances, proper

anywh~re

is

supplied 10.5 kV from the high voltage

between

goes

of

also

to

supply.

3.4 HIGH

VOLTAGE The high voltage supply source that requires only

POWER

SUPPLY

is

a self-contained high voltage

line voltage input. The input actually the split primary of its own internal step-up transformer. For 115 V operation, the primary windings are operated in parallel; for in series. The step-up transformer delivers high voltage

230 V operation, they are operated

ac

to

a voltage doubler and filter. The ultimate dc voltage

10.5 kV and unregulated. Thus, the high voltage

is

slaved to

the line voltage, and varies linearity with it.

is

The W684 Intensity Control

is

used

in

the VR14L and VRI7L. In the W684 (Figure 3-4 and drawing D-CS-W684-O-1), the three intensity signals [Intensity to

grid

1.

(Operation

Paragraph 3.5.) The bias voltage applied to grid 1

in CRT may vary from determined by the setting

Intensity on the screen the W682/W684 card. held at +62 V. The +62 V the W682/W684. +62 V on the cathode this alone does not determine brightness, since intensity related to grid-to-cathode voltage. Thus, the cathode

the voltage at pin E

(2:0)] , before it

of

W682/W684 circuitry

-80

Vdc to 0 V, the upper limit being of

R38 on G836.

is

generated by cathode pulses from

When

not intensifying, the cathode

is

derived from the +80 Vdc at

When

the beam

is

grounded, or made 0

is

"modulated" by

is

sent

is

explained

of

the

is

to be turned on, the

V.

However,

is is

constantly going between +62 V and 0 V but, depending on

is

where the grid voltage (brightness potentiometer)

set, the

beam may never be on, dim, or very bright.

Grid 2 The

of

400 V

the CRT

is

operated at approximately +400 Vdc.

generated from the 150 Vac tap

of

the power transformer by a voltage doubler on the G836 board. The ac passes through

C 14 and

is

prevented from going negative by D9. This causes the entire peak-to-peak voltage to become positive. D 1 it; the resultant output

0 rectifies this voltage and CIS filters

is

+400 Vdc. The 400 Vdc

goes

is

Because the electron beam voltage, the ability to deflect the beam will change

If

high voltage changes.

a constant deflection current flows through the yoke, the amount the anode high voltage

accelerated by the high

of

deflection

is

increased (smaller displayed

is

reduced

as

the

picture); the deflection grows if the anode high voltage decreases (larger displayed

is

factor change of

the old anode voltage to the new anode voltage, i.e., deflection factor voltage

is In terms mately

0.4

proportional

= ".;V 1 /V;.. For example, if the high

halved, the deflection would grow 1.414

of

line voltage, the deflection factor

of

the change, i.e., a 5 percent line change

picture). The actual deflection

to

the square root

of

the ratio

('\/2/1).

is

approxi-

causes a 2 percent deflection change.

The

VRI4/VRI7

unit from possible damage due to arcing. Arcing

incorporates circuitry which protects the

is

due

to

transient conditions within the CRT, which cause a spark to

jump between the anode and other

protection circuitry consists

(DEC

suppressors

W684

, R43 on G836, R9 on W682, and a

mounted on the

part no.

CRT socket. The resistors act

11

CRT elements. The

of

two voltage transient

11562), R30 and D13 on lK

resistor

as

current

limiters; diode D13 prevents grid 1 from becoming more

0

V;

positive than mounted on the electrode from exceeding

the voltage transient suppressors,

CRT socket, prevent grid 2 and the focus

+600

V.

if

3-6

RI

560

R2

1.78K lIBW

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[

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BL2

NOTE:

This schematic rna)' not reflect

most-

recent engineering changes

TNESS

R38 100K 34W fO% 76PR

CP-8763

Figure 3-2 G836 Circuit Board,

Part

of

the 7007165 Power Regulator Assembly

3-7

~-SIGNAL

J----~~~----~~----e_--~r~

RI

100

+ CI

6.8

MFo 35V 10%

01

D5

+

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fil2

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+

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OUT

014 IN3039B

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C---------.------e-----,r--e-------r---+--+----~~--~--_+-------------------------e------~---------e~--------_e--~------~

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R

+5V

A---------+------+-----~--~----~~~

D3

.--------------------P

TO

CHANNEL

SELECT

SWITCH

~-SELECT

L~~rvv-+-----~~--~~----------------~~

I-DIRECT

R3

100

RIO lOOK

I

N PUT D

--------

.......

---------------------H--------

.....

-------------------

F

TO

GRID

1

UNLESS OTHERWISE INDICATED:

DIODES

ARE

D664

CAPAC ITORS ARE

100V,20%

E I

IS

DEC7400N

PIN 7

ON

IC = GND

140N

IC=

+5V

RESISTORS

ARE

1/4W,

10%

NOTE:

C5

.047

MFo

10%

200V

R9

lOOK

'-------------------E

TO

BRIGHTNESS

POT

SLIDER

This schematic may not reflect

most-recent

CP

-0764

engineeritg

changes.

Figure

3-3

Intensity Amplifier W682, Circuit Schematic

Z INPUT

CATHODE

GENERATOR

PULSE

~

+80V

62V

>-------L----..CATHODE

+5V---"-'"

+80V---

I

NT

0 L

------4["1

INT 1 L

------4["1

INT 2 L

NOTE

lOne

of eight intensi

levels

as

by the three intensity

inputs.

NOTE 2 Brightness determined

by

grid

1 voltage which

is a function

intensity

and BRIGHTNESS posit

ion.

LOW-VOLTAGE DETECTION

.....

INTENSITY GENERATOR

of

ty

the

pot

determined

level generated

+5V

LEVEL

IL

Figure

NOTE1

34

W684 Intensity Control

3.5 W682 AND W684 INTENSITY CIRCUITS

In the cation circuit board. The intensity signal is 9, 10) output coupled through exponentially decays to is input to gate B (pins 11, 12, and 13). Also, the channel select information which comes from pin

VRI4

without the light pen option the intensifi-

of

points on the screen

is.

a transition from a high to a low.

is

controlled by the W682

signal

is

routed to pin J. This

While

the

Z-signal

at a high (above +2.4 V), the output from gate A (pins

is

low.

When

of A goes

determined by

the Z-input

high. This positive-going transition

C2

and becomes a positive spike that

o.

C2

and R4. This positive-going spike

is

low momentarily, the

The time constant

as

of

this decay

input to

is

B,

8,

ac

the

R.

This information either enables gate B to respond to the

is

intensification spike or not. Assuming B R, the positive spike causes the output This low remains

~r

high threshold level.

1

as

long

as

the input spike to B

As

soon

as

the threshold, B's output immediately reverts

is

state. B's output

fed back to A's input (pin 10) to allow

enabled from pin

of

B to

go

to a low.

is

above its

the spike decays below

to

the high

A's output to latch high, thus not requiring A's input (pin

to

remain low, but rather be a momentary drop from a

9) Of

high.

course, when the spike decays at

B's

input, the

GRID

LEVEL

>------

-8()V~

NOTE 2

....

CONTRAST

r--

/GENERATOR

-,

I

BRIGHTNESS I

'='

L

__

latching input respond to the next negative-going transition on the Z-intensify input.

during the negative-going transition that occurs when A

resets. Gate pulse to drive the output pulse amplifier Q 1. Gate normal1y

"grounds" out the base drive for off. though there

output to

is

+80 V dc, but D7 begins to conduct at +62 V clamping the

collector at +62

+80 V across R8 and Zener diode D14. tied through absence This, along with the negative bias on the grid, keeps the

CRT beam shut off.

C's output goes high, allowing Q I

from the base drive turns on

cathode

FRONT

J

PANEL

---

BRIGHTNESS I

PRESET

-80v

__

I_~

!f!3~

J

is

removed from A (pin 9) thus enabHng A to

DS

C (pins

is

low until a pulse comes along. This low

DI3

and DIS guarantee that QI will be off, even

is

a residual voltage drop across D6 and the

of

gate

C.

QI's

+80 Vdc. With

QI

V.

RI2

to

of

an intensify input, the cathode resides at +62

+80Vdc

of

the CRT) to

CP-0761

clamps the input from going negative

1,2,

and 3) simply inverts the intensify

QI;

therefore, it

collector

is

tied through R7 and

off, the collector tries to ride up to

The +62 V

is

generated by dropping the

QI's

the CRT cathode. Therefore, in the

When

an

via

intensify

D17,

Rll,

QI,

causing its collector (and the

go

from +62 V

signal

to

receive base current

RS,

DI3,

to 0 V.

GRID

1

will

D8

collector

occurs, gate

and DIS. This

This turns

C

be

is

V.

3·10

the CRT beam on. The duration detennined by the time constant 300

ns.

D16 prevents the voltage supplied to

is

exceeding S V; this

necessary to prevent damage

of

this intensify pulse

of

C2, R4 and

is

normally

RS

to

from

gate

C.

When

power

is

removed from the

prevented from blooming and possibly burning the phosphor. Blooming can occur because the necessary voltages (±80 Vdc) that keep the CRT shut off, drain to 0 V faster than the high voltage supply. voltage becomes more positive than cutoff, the on very hard. D8 and When

power

is

turned off, the +80 V goes

doing,

C4

hangs on to its voltage and thus back biases D8 which does not allow like

Ql

's power source, allowing the collector (and CRT

cathode)

to

hold at +62 V which

condition. Eventually

C14 prevent this from happening.

C4 to discharge.

C4

discharges; however, by that time the high voltage has also discharged, rendering the safe.

Five volts are supplied at pin A for for D16. A

11, and D inputs from exceeding

+3

V logical 1 level

12

through R2.

D2 +S

inputs from becoming negative.

The two remaining inputs on the W682 are the Z-select and Z-direct. The Z-select to

be multiplexed or time enabled.

whether or

not

is

a bit

the intensity pulse output through gate B depends on whether or not a high input

is

available at pin continuously available, independently when the channel select switch When

the channel select switch intensification occurs only when a high Z-select and an intensify input channel select switch

is

in the 2 position, gate B

only when the Z-select input

The Z-direct

is

an input directly to the grid through

Video or other time varying brightness information may be

coupled to the grid at pin

In the event

of

D.

a failure deflection ceases and a bright spot could occur on the causing a burn. To prevent this, G838 (Figure 3-5) contains a circuit that supplies +22 V or - 22 V

goes

+5

to 0 (in the blown secondary fuse), the circuit supplying the down. Because the G838 has a low value resistor across the

n),

5 V (47

the 5 V line (pin

VRI4,

When

the CRT must be

the grid-to-cathode

CRT turns

to

0 V but, in

C4

momentarily acts

is

the

safe

El

and also

is

generated across D9, 10,

and

D3

protect gate A and gate

V.

Dl

and D4 prevent the same

that

allows the intensity pulse

As

mentioned before,

is

allowed to

13

of

gate

of

the Z-select input,

is

in the 1 & 2 position.

is

in

is

presented.

as

pass

B.

This high

the 1 position,

is

presented at

When

is

a low.

of

either the ±22 V supplies,

V to the W682.

case

If

either the

of

a short circuit or

+5

A)

on the

W682

is

grounded.

so

or

off

CRT

a clamp

to

the

is

the

enabled

CS.

CRT,

V shuts

is

This causes the base drive to Ql

through D16 and renders

-22

V

K

R4 R3 2K

1/2W

R5 100

V-'~--------~----~

UNLESS OTHERWISE INDICATED:

RESISTORS=1I4 W,5"lo

Figure

In the VR14L and

is

the screen

controlled

Ql

3-5

G838 Circuit Diagram

VRI7L,

by

to

be shunted to ground

off; this shuts off the CRT.

+

22

V

U

4.7K

R6

47

112W

the intensification

the

W684

module. The Z-input intensity signal enters the W684 at pin J (drawing D-CS-W684.Q-l). Before the Z-input TTL high. The output AND

gates, E2 pin 6 and E2 pin 11. This causes

off

cut

and Q6 because its base cathode voltage at pin +62 V, and no beam

of

E2 pin 3

to

conduct. Consequently,

is

low at this time. With

U

will

is

generated. The cathode voltage

produced by the Zener action

is

asserted, pin J

is

low, disabling the two

Q2

be positive, approximately

of

D4 from +80 V input

from the G836.

When

the Z-input pin 6 and E2 pin reversed:

Q6 conducting, to

conduct. The cathode voltage goes from +62

+5

is

asserted, E2 pin 3

11

are enabled. Now the situation

is

cut

off

REG

is

coupled to the base

and

Q7

is

disabled and E2

conducts.

of

a beam can be produced, provided one other condition satisfied - grid 1 must be sufficiently positive before the grid-to-cathode voltage results in a beam strong enough to cause screen fluorescence.

Grid voltage can be varied from approximately almost more positive.

brightest when

increases, the image becomes dimmer.

0 V; brightness increases

Q3

controls the grid voltage with the screen

Q3

is

cut off.

as

the voltage becomes

When

Q3

Conduction

determined, along with the contrast control setting, by the

voltages present at the base

of

Q4 and the emitter

+5V

p

CP-0757

of

points on

is

Q7

to

Q2

is

cut off

cut off, the

With

Q2 causing it

to

0 V and

-80

conduction

of

Q3

of

Q5.

a

be

is

Q7

is

to

is

3-11

The voltage panel brightness control. Turning this control clockwise

causes Q4 more positive. As a result, the, base positive. Coincident with this, the emitter voltage

determined

[Intensity (D8, D9, and through a voltage divider consisting Table sity levels and the resultant brightness level. of

levels asserted increases from 0 through level increases from level, harder Q5 conducts. is

dropped over causing the base turn,

voltage approaches

Figure brightness levels, brightness control, which can be changed Reference A shows brightness control setting, for each

As

the

in brightness at each level (reference B).

The contrast control,

As

Q5. voltage, the brightness range between brightness level brightness level 7 increased. This reference A

at

the

base

of

Q4

is

established by

to

conduct less; the emitter voltage becomes

of

Q3 becomes more

by

the

state

of

the

three intensity level signals

(2:0)

L] . These signals forward bias three diodes

DI0)

that

control

3·1 shows the relationship between the three inten·

0 through 7. The higher the brightness

the

more positive

decreases Q3 conduction and the emitter (grid 1)

3-6 illustrates

control

the

to

is

control

is

reference C;

the

As

Q5 conducts harder, more voltage

the

Q4,

of

Q3

to

0 V.

the

that

are program controlled, and

the

turned c1ockwise, there

R19,

is

turned clockwise, dropping more

is

increased; i.e., the image contrast

indicated in Figure 3-6

the

conduction

of

R21, R22,

emitter

R18,

become more positive. This, in

relationship between

relative brightness at a particular

of

Q5

and

R19, and R29 network,

of

the brightness levels.

is

is positioned between Q4 and

as

the

original brightness spread

the

front

of

Q5

of+5

REG

and R23.

As

the

number

3,

the

brightness

therefore the

the

eight

the

by

the

operator.

a linear increase

0 and

the

change from

is

(x) is increased (y). Actually, level 0 becomes dimmer and

the

level 7 becomes brighter. Therefore,

brightness control

must also the result

Note intensity levels generating a brightness level (one that setting. At determines the difference in brightness between the ness levels.

2L

H H H H H L

L L H L L L

In case the

If

these circuits were condition occurred, the phosphor would be burned and the screen damaged. This are disabled

beam would be continually directed the to

about +4 V, Q9 loses forward bias and ceases

be

adjusted at

decreased lower intensity levels. Reference D shows

of

this final adjustment.

that

grid 1 voltage

is

then

combined with

the

same time,

Intensity Level

IL

H

L

H

L

of

a decrease in the

cathode and grid circuits described above are disabled.

by

the same power failure and the electron

screen.

If

the

+5

the

same time

is

the

consequence

the

particular brightness control

the

Table

3·1

Brightness Control

Brightness

OL

H

L 1

Level

0

to

compensate for

of

the three

of

eight)

contrast control setting

bright·

Front

Panel

Brightness

Control

H 2

L 3

H 4

L 5

H 6

L 7

+5

or +80 V

not

shut

off

is

because X and Y deflection circuits

V input from the G840 at pin A drops

input

to

the

W684,

when this low voltage

to

the

same spot on

to

conduct.

the

i

IMAGE

BIGHTNESS

Figure 3·6

VRI4L/VRI7L

r-.J

I

r-.J

I 3 y

r-.J

D--~

~

__ 2 _________

Brightness and Contrast Control

3·12

r

--

I

r-J

I 7

r-J

I

J

r-

I

l

_

CP-0584

Effectively, this opens the

+5

V input to the emitter

of

Q7

(cathode circuit) and to the R21, R22, and R23 voltage

divider (grid 1 circuit). The same result occurs

input

to

the cathode circuit fails. In this instance, the base

of

Q9 becomes more positive;

Q9

is

cut

off

if

the +80 V

and the

+5

V

input opens.

3.6

LIGHT

PEN

AMPLIFICATION

The input from the 375 Light Pen that results from detection

beam intensification

is

not usable in its analog

of

form; it must first be converted to a TTL compatible signal.

is

This

the prime function

module (drawing

D-CS-G840.o-1 and Figure 3-7).

of

the G840 Light Pen Amplifier

When

power

is

removed from the VR14L/VR17L, the CRT must be prevented from blooming and possibly burning the phosphor. Blooming can occur because the necessary voltages faster than the high voltage supply.

(±80 V), that keep the CRT shut off, drain to 0 V

When

the grid-to-

cathode voltage becomes more positive than cut-off, the

C1

CRT turns on very hard. D2 and

When

power

is

happening.

o V

but,

in

so

dOing,

turned off, the +80 V goes to

Cl

hangs on to its voltage (+60 thus back biases D2, which does not allow C1

momentarily acts like

emitter (and CRT cathode)

off

safe or

condition. Eventually

Q1

's power source, allowing the

to

hold at +62 V, which

prevent this from

Cl

to discharge.

C1

discharges; however,

V)

is

and

the

by that time the high voltage has also discharged, rendering the

CRT safe.

+3V

Jl

PEAKING

CIRCUIT

In relation to the

as

a variable resistor that presents a low-going signal at the input (11, pin occurs within the light pen's angle negative-going analog signal by the circuit at the collector

G840, the light pen phototransistor acts

3)

to the module when screen intensification

of

acceptance. This

is

inverted by

of

Ql,

and peaked

Q1. The signal, now

positive-going with a greatly decreased rise time (about

1

ps),

is

differentiated before being input

to

the

LM

Comparator .

The

LM

306

is

a high-speed voltage comparator designed produce a sharp-edged, TTL compatible output when the input attains a predetermined threshold voltage. In this

to

the

LM

application, the (+) input about

.,

400 mY.

,t1

When

~400mv

--~N-··

ov-I

DIFFERENTIATOR

'"

306 (pin 2)

the differentiated input at the

"1

5v

i I

+

U

ov

VOLTAGE

COMPARATOR

is

t1

r

,

306

to

held at

(-)

ENABLE L

9602

SINGLE

SHOT 0 SHOT 0

L--

__

Figure 3-7 Light Pen Amplifier

3-13

LIGHT PEN

~

9602

SINGLE

PULSE

1

L

CP

-0759

input

r.eaches

is

produced at pin 7, provided

at

E3

pin 13. This qualifying

hits (LIGHT

this threshold, a negative-going output signal

an

ENABLE

signal

ensures that

PEN PULSE L) from the G840

signal

is

present

all

light pen

are

valid, inhibiting those hits that might be generated by spurious noise from the light pen. The 30

ns

after the two input voltages compare approxima tely 20 ns) and remains low input stays above the 400

is

time

indicated in Figure

LM

306 output occurs about

(fal1

as

long

mV

threshold. This assertion

3-7

as

t1. Positive feedback

as

time the

(-)

provided from the output to the (+) input to assist the input signal comparison.

LM

The negative-going output from the stage

of

a 9602 Monostable Multivibrator, which, in this application, functions output signal, LIGHT signal from the of

the 9602 triggers the second stage, also configured

single-shot. The 1 output

70

IlS,

inhibits a second light pen hit immediately following

as

a single-shot to produce

PEN

PULSE L. Coincident with this

0 output, the 1 output from the first stage

of

the second stage, high

306 triggers one

alSO

ns

as

for

the first one.

is

Timing for this operation

comparator output assertion time

only the negative-going transition

LIGHT

PEN

PULSE

L.

shown in Figure 3-8. The

is

unimportant because

is

needed to initiate

is

In the event

ceases burn. To prevent this, the circuit on the produces

disabled

of

a short circuit or blown secondary fuse). Referring to

drawing

of

a failure

of

either 22 V supply, deflection

and a bright spot occurs on the CRT, resulting in a

G840 module that

+5

V for the W684 intensity module

if

either the +22 V or

D-CS-G840-O-1,

-22

if

+22 V fails,

V goes to 0 (in the

Q3

bias (at the emitter) and turns off, shutting down the

If

the

-22

is

base

of

Q3

V goes to 0,

goes

high. This causes

Q2

loses

emitter voltage and the

Q3

to turn off and

drops. This circuitry (aside from some component values) identical to the fault protection circuitry on the G838

(Figure 3-5). Note that this failure detection circuit addition to the

W684

low

+5

V voltage protection circuit

previously described (paragraph 3.5).

3.6.1 375 The 375 Light Pen is

a

D-CS-5410268-O-O)

Light Pen

is

recess-mounted

in a polished cylinder approximately

simply (;onstructed. A phototransistor

(drawings

C-UA-375-O-O

0.45 X 5.0 inches. The output signal connection

cable that plugs into the VR14L/VRI7L front panel. an intensified beam strikes the CRT phosphor where the light pen and negative-going alternation

is

being aimed, the phototransistor

is

output to the G840 Light Pen Amplifier module (Figure 3-7). In the G840, the light pen output LIGHT PEN PULSE

is

shaped to become the TTL compatible

L.

loses

(Ql)

will

be

case

forward

+5

V.

+5

is

and

is

via

When

conducts

signal

V is

in

a

COMPARATOR

1.

LIGHT

This

(E4

PEN

(E2-6)

(E2-10)

output

OUTPUT

PULSE L (E1-3)

NOTE:

-7)

must

~-------------~70~s--------------~·1

L......-_~~~

~-----------70~s------------~·1

~

be

low

before a second

Figure

3-8

LIGHT

PEN PULSE L

signal

can

be

Light Pen Pulse Timing, G840 Module

3-14

asserted.

CP-O!i71

CHAPTER

4

MAINTENANCE

This chapter deals with the prevention, diagnosis, and repair of

fault conditions. Successful troubleshooting VRI4/VRI7 milliampere meter; however, expedites isolation and repair

PREVENTIVE MAINTENANCE

4.1 VRI4/VRI7 that the equipment flow for cooling and a periodiC, cursory inspection for abnormal hardware conditions. Because dissipation on the deflection and regulator heat sinks, good

air flow must be maintained. A periodic check

to see obstructed by dirt, dust accumulation, or inadvertently blocked by external equipment or surfaces.

Prolonged off-screen deflection

damage the signals into the

screen because

4.2

TROUBLESHOOTING VRI4/VRI7 be done with a volt-ohm-milliampere meter; however, an oscilloscope will be needed

When making voltage measurements malfunction VR

oscilloscope) leads to the test points, then and reading may be taken. very brief moment.

tions may be discovered without causing further damage. Never leave power on to a malfunctioning or repaired all necessary checkpoints are measured and proved nominal.

can be performed using a volt-ohm-

an

oscilloscope facilitates and

of

faults.

preventive maintenance consists

is

getting and maintaining proper air

of

that

fans are operating properly and are not

of

the CRT beam can

VRI4/VRI7.

VRI4/VRI7

of

intermittent incorrect signals.

voltage checks (Table 4-1) and most tests can

off

very quickly so that the anticipated

Ensure that the X and Y driving

never drive the CRT beam

if

waveform analysis

NOTE

14/VRI7,

to

the proper range, connect the

set the voltmeter (or

tum

the power on

Power

is

only on for a

In

this way, fault condi-

VRI4/VRI7

of

the

of

ensuring

the power

is

required

off

is

required.

on

a

until

The circuit card connector block,

is

side, section, and shows pin and connector locations for

4.2.1 No Picture Probably equipment can be caused by almost any malfunction such input intensity pulse, incorrect input deflection signals driving the beam failure (thermal cutout). The following sequence

leads

labeled

the most common failure mode with this type

to

the isolation

1.

2. Remove

3. With a voltmeter (or oscilloscope), measure the

4. Set up to measure

AO

1 and A04 left to right on the top

BOI

to

B04 on the

is

"no

picture." Unfortunately, this condition

off

the screen, a power supply fuse, or fan

of

the fault(s):

Check fuses.

continue. then continue. leave power on only long enough to complete

each check in this procedure.)

and all modules except W682/W684 and G836.

+22 Vdc

can be measured between

A02-V which

shut down power. the regulator has a fault; refer to Appendix A.

If

0 V or below +20 Vdc occurs, the +22 V

overloaded; continue

between ground. Momentarily apply and shut down power.

-22

Vdc, the

to Appendix

V

is

- 22

If

not, replace any that are blown and

all

input signals at the rear

(20 Vdc to 22 Vdc

is

AOI-K (blue wire) and A02-V which

If

the - 22 V

-22 A.

overloaded; continue to next step.

as

viewed from the wiring

bottom

they are in good condition,

(If

a blown fuse

ground. Momentarily apply and

If

the +22 V

to

-22

V regulator has a fault; refer

If

20 V or more positive, the

section. Figure

PI,

P2,

P3

and P4.

as

a loss

of

events

is

replaced,

of

the unit

is

acceptable). This

AOI-U (red wire) and

is

above +22 V,

the next step.

V. This can be found

is

more negative than

4-1

of

is

4-1

VRI4/VRI7

Table

4-1

Voltage Check Points

Circuit Block Pin

A02A A03A

A02E,B A03E,B AOIU AOIK AOIP

Deflection Heat Sink Pin X-Axis

P5

- 2

P5

- 1

P5

- 3

P5

-4

P5

- 5

Y-Axis

P5 P5 -15 P5 -13 P5 P5 -11

Regulator Heat Sink Pin

P3 - 1 P3 - 2 P3 - 3 P3

- 12

P3 -

11

P3 - 10

- 14

- 12

Voltage

*2.2V nominal *2.2V nominal * * +22 Vdc (Red)

-22

Vdc (Blue)

+5

Vdc

Voltage

+21

Vdc +22 Vdc *<

IV

-21

Vdc

-22

Vdc

Voltage

+43 V dc Orange +42 V dc Gray/Yellow +22

Vdc Red

-43

Vdc Green

-42

Vdc Gray/Blue

-22

Vdc Blue

Signal/Control

X Current Sample Y Current Sample X Input Signal Y Input Signal + Regulated dc

- Regulated dc For W682/W684

Component

Base

PNP

(2N4399)

PNP Emitter (2N4399)

All

Collectors

NPN

Base

(2N5302)

NPN Emitter (2N5302)

Component

Emitters Bases Collectors Emitters Bases Collectors

of

2N4399

of

2N5302

2N4399

of

2N4399

2N5302

of

2N5302

7007165 (G836) Regulator

Circuit Connectors

PI

- 1 PI - 3, 6 PI - 4 P2 - 1 P2 - 2, 4, 7, 9 P2 - 3 P2 - 5 P2 - 6 P4 - 1 P4 - 2, 14 P4 - 3 P4 - 4

P4 - 5 P4 - 6

*Indicates voltage depends

PI,

upon

P2, P4

input

signal.

Voltage

+43 Vdc Ground

-43

Vdc

3.5 Vrms Ground

3.5 Vrms 70 Vrms (200

150 Vrms (400

P-P)

P-P) +22 Vdc Red Ground Black +22 Vdc Red

o Vdc Black

-

80

to

+400 V dc Gray/Red

+400 V dc Orange

4-2

Signal/Control

Raw + dc

Raw - dc 1/2 Filament

Filamtmt

1/2

±80V

tap +400V tap + Regulated

Hot + Sense Cold ± Sense Focus Grid 2

7007165 (G836) Regulator

Circuit Connectors

PI,

P2, P4

Table

VRI4/VRI7

4-1

(Cont)

Voltage Check Points

Voltage

Signal/Control

-7

P4 P4 - 8 P4

·9 P4·10 P4·11 P4·12

P4 - 13

P4·15

3.5 Vrms Brown

3.5

-

o to

+80 Vdc Gray/Orange

-22

o Vdc Black

-22

Note: All voltages measured with respect

Pl

5 2 6 3 9

EJ

P2

7 4 8 5 2

6 3

10 11

12

Vrms Brown

80 V dc Gray/Green

-40

Vdc Gray/Violet

Vdc Blue

to

ground (chassis or A02V).

P3

7

4

8 5 2

9 6

3

13 14

15

Filament Filament

To Brightness

Brightness Preset For

W682/W684 Hot· Cold·

- Regulated

P4

7 4

10 11

8 5

12

9

6

Sense

2

3

Potentiometer

HIGH

VOLTAGE

POWER SUPPLY

7007165 (G836

W/CONNECTORS)

8RIGHTNESS PRESET

Figure

ADJ

4-1

FOCUS

VRI4/VRI7

4·3

ADJ

Interior View

6582·5

5.

With

an oscilloscope or meter, measure ±2.2 V maximum at A02-A with respect to ground (A02-V). This point (A02·A)

is

the X·axis deflection coil current sample. Because coil current flows through a measured at

A02·A multiplied by two equals

0.5 n resistor, voltage

the current flowing. With the A225 circuit cards removed, no coil current should flow. Momentarily turn on power to the VR14/VR17. minus (refer

power transistor probably

6. Measure the same deflection coil current at

ground

VR14/VR17 power on and off. should be read; this indicates no coil current observed, refer to Appendix deflection transistor

If

A02-A has any voltage plus or

to

Appendix B), a deflection

is

shorted.

as

in step 5 for the Y-axis

A03-A with respect to

(A02-V).

Momentarily

Y -deflection

is

flowing.

If

any voltage

B,

since a Y·axis

is

probably shorted.

No

7. Replace the G838/G840 circuit into the A225 circuit into Y-axis,

±2.2

A03 board out.) Measure

V at pin A02·A with respect

A02. (Still

(A02-V). Momentarily apply power.

is

voltage

within safe limits (within ±2.2 V),

leave power on and adjust the position potenti-

ometer on the A225 circuit. change the voltage reading on

the

A225 indeed

is

controHing the coil current.

Return the position potentiometer

If

nal position.

V, shut down immediately. Because the

±2.2

the voltage at A02·A

DOing

A02·A, providing

to

position potentiometer on the A225 can drive more current than the ±2.2

is

(4.4 A), it

possible that it (the position

V limit signifies

potentiometer) has been adjusted extreme or the other. To prove whether this the

case

or

if

the A225 circuit board turn the position potentiometer lows: clockwise very negative; counterclockwise

if

the voltage at A02·A

if

the voltage at

A02·A was very positive. If no change

A02-A after adjusting the position potenti-

at

is

ometer, the A225 board replaced or repaired (refer

8. Repeat the same tests

faulty and should be

to

Appendix C).

as

in step 7 for the Y-axis deflection circuit A225 plugged into Monitor A03·A. Refer

to

Appendix C for A225

repair.

turn

voltage

is

A01

and

leave

the

less

than

to

ground

If

the

this should

its origi·

is

beyond

to

one

is

faulty,

as

fol·

was

is

noted

A03.

9.

If

the fault has not been isolated, the intensity circuit W682/W684, the electrode voltages, and the high voltage supply are suspect. The output of

the W682/W684 drives the cathode. At rest,

it should be +62

V and, when triggered,

go

to

approximately 0 V.

To check the W682, apply a proper Z·input (+3

V to 0 V transition) at J17 pin 4 and check

to

see

that the

signal

reaches A04·J.

If

so, check

A04-R with the channel select in the 1 & 2 position so, A04-A G838 module developed.

Sf!e

to

see

that a high

that

is

+5 V is

less

If

being supplied to A04-A.

than +4 V replace or repair the

as

this

the three preceding measurements

is

present there.

is

where the

If If

+5 V is

are good and the W682 output (measured at A04-U) least

is

not going from +60 V

to

0 V for at

300 ns, repair or replace the

W682

module.

To check the W684, apply Z-input at J17 pin 4 and check to

reaches

A04-J.

supplied to

If

A04-A.

so,

If

replace or repair the G840 module,

where the

+5 V is

0 V (ground)

see

that

A04-A

is

developed.

see

+5 V is

less

than +4

If

to

the

that it

being

as

this

the two

V,

is

preceding measurements are good, and the W684 output (measured at approximately

0 V, repair or replace the W684

A04-U)

is

not at

module.

10. Measure 6.3 Vac between P4-7 and P4-8 and observe the glowing filament on the

Vac can be traced back to the power

6.3 transformer by way

11. Measure the grid 1 voltage at vary from -

is

when the front panel brightness control

80 V dc

varied. The

of

P2 pins 1 and 2.

A04-F.

to

between - 30 V and 0 V

-80

Vdc comes from the G836

CRT. No

It

should

is

board. Trace back to the G836.

12. Measure grid 2 at P4-6. It should be at least +300

V.

Trace back to the G836.

13. The last item operating improperly for picture" Generally,

is

the high voltage supply itself.

all

other measurements should

"no

be made before considering the high voltage, since the majority

of

"no

picture" conditions

wiJ) not be caused by the high voltage supply. Measuring the high voltage directly

is

extremely

4-4

dangerous and not recommended. Instead, a

is

quick method

to take a long screwdriver and ground the blade with two separate clip leads for safety. Turn the seconds and then

SHUI' IT OFF. After it ground out the anode cap on the GROUNDED screwdriver.

10 seconds after power

should occur

CRT was charged with high voltage.

the

to

the screwdriver indicating that

arc occurs, replace the high voltage supply.

4.2.2 Faulty

Picture

a. No Focus - Check the range

potentiometer focus voltage at

on

P4-5 potentiometer through its range. range

is

+350 Vdc

repair.

b. Half or Quarter

of ally, this condition indicates two deflection transistors only half deflection in question can be identified by observing

of

which side left and

the screen

bottom

controlled by the

on

tors

the deflection heat sink. These are the lower two transistors; the left side is

controned

(if

the deflection heat sink front the screen power transistor.

of

by

the left lower power transistor

the

VR14/VRI7),

is

controlled by the right lower

Of

are controned by the

of

side

the heat sink controlling the upper screen, the left side the right screen.

The remaining possible faulty picture patterns,

c.

as

such

picture swim (60 Hz), oscillations,

distortion, etc., will be restricted generally

improper input signals (especially grounding

or

techniques) If

input signals are not suspect, a faulty A225

faults on the A225 circuit board.

may be isolated by swapping X and with one another axis.

VRI4/VRI7

on for 5

is

off,

CRT with the

If

done within 5 to

is

turned off, an arc

If

no

of

the focus

the G838 by monitoring the

while adjusting the focus

Minimi.1m

to

-60

Vdc. See G836 for

the Picture Missing - Gener-

that

one

of

the

is

not

working; thus,

is

available. The transistor

is

not working. The

portions

of

the

screen are

PNP (2N4399) power transis-

of

the screen

is

viewed from the

the lower part

of

course, the upper and right

NPN

(2N5302), the right

of

the heat sink controlling

to

Y A225s

to

see

if

the problem changes

d.

If

a weak picture

on

all sides

that

is

deflected

is

encountered, with excessive jitter

off

the screen

and ripple, the high voltage supply should be

replaced.

4.3 ASSEMBLY REPLACEMENT INSTRUCTIONS Other than the G838/G840, A225s, and W682/W684 circuit· modules, most repair and replacement will involve the G836 regulator subassembly; the regulator heat sink assembly; and the deflection heat sink assembly; and, in rare cases, the high voltage assembly, yoke, and cannot be stressed too strongly that the

VR14/VRI7

CRT. It

line

cord be removed from the line before doing any mainte-

off

nance. Turning power

or removing fuses does not render the unit safe from shock hazards, since the power switch and fuse interrupt only one side

is

the other side

is

cord

plugged in. Do not take chances, UNPLUG the line

permanently connected

of

the ac input line voltage,

as

long

as

the line

cord.

NOTE

Photographs in this section are

but

prototype, VR1'

configurations.

4.3.1 Deflection Heat

generally apply

Sink Removal

of

a VR14

to

all VR14 and

To remove the deflection heat sink (Figure 4-2) proceed follows:

all

1. Remove the line cord and

circuit modules above the deflection heat sink assembly (G838/G840, A225s, W682/W684).

2. Remove the four 6-32 screws that hold the heat sink assembly to the rear chassis plate.

3. Lift the assembly out

to

make room for removing the assembly cable connector. The IS-pin connector retaining tabs on each side that when the connector through the square holes that they were

is

removed by squeezing the

of

the connector so

is

pulled, the tabs pass

butted

against. Do not pull the connector by its wires,

by

only

its plastic body.

as

4-5

a.

Remove circuit boards and the four 6-32 screws

holding the deflection sink

to

the rear panel.

b.

Remove heat sink assembly (and its connectors necessary) and remove faulty power transistor.

BNC

Later models do not have the four

of

the top rear

the unit.

connectors at

Figure 4-2 Deflection Heat Sink Removal

4-6

if

4. To remove a faulty transistor, unscrew the two 6·32 screws that hold the transistor down. Then pull the transistor straight out from the socket. Apply an even coat (approximately 1/32 inch thick) surfaces transistor, making sure that the base and emitter pins are oriented properly; otherwise, the transistor screw holes. Also, ensure that the insulating washer sink and each mounting screw has a star washer.

7007165 Power Regulator Assembly Removal

4.3.2 . The 7007165 Power Regulator Assembly comprises a G836 regulator printed circuit board with a mounting frame for

11

, J2, J3, and J4. To remove the 7007165 Power

Regulator Assembly proceed

1. Remove the line cord and (G838/G840,

2. Remove

7007165 by squeezing the two locking tabs on

of

thermal compound to an mating

of

the new transistor. Replace the new

case

will not align with the two

is

between the transistor and the heat

as

follows:

all

circuit modules

A225 , W682/W684).

all

four cable connectors (Figure 4·3)

coming into the connector bracket on the

the sides connector straight up, allowing the locking tabs to butted against. wires; only by its plastic body.

of

each connector, while pulling the

pass

through the square holes they were

Do

not pull the connector by its

3. Remove the two mounting screws for the 7007165 from the opposite side 7007165 chassis wall.

4. The 7007165 straight out.

The 7007165 has +80 Vdc, +400 V dc available on it. These voltages do not disappear immediately when

power

is

when throubleshooting the board.

5. For troubleshooting, the 7007165 may be

operated outside its normal mounting position by laying the board flat and reconnecting the four cable connectors. Ensure that the etch side of

the module does not touch the chassis, causing short circuits, by insulating the board with a book or piece Figure 4-4b.

is

WARNING

shut off.

now free and may be pulled

-80

Use

extreme caution

of

cardboard

of

Vdc, and

as

shown in

the

NOTE

When placing the 7007165 back into the unit, ensure that the bottom circuit board rests in the slotted groove insulator block provided on the bottom chassis.

of

the

TO

VR14

I

J2

I

J4

G836

REGULATOR

BOARD

I

~

J3

~

J1

I

Jffij

W

TO

TRANSFORMER

Figure 4·3 7007165 Power Regulator Assembly

TO

AND

DIODES

FILTERS

TO POWER

SUPPLY

HEAT

SINK

~

12-0331

4~7

a.

Remove power cord and

all

connectors to the

7007165. Unscrew mounting screws from the of

opposite side

the vertical chassis wall.

b.

Reconnect connectors and place a cardboard under the

7007165

to

prevent shorting

out

the circuit against the chassis when troubleshooting the board outside the unit.

Figure 4-4

7007165 Removal

4·8

4.3.3

..

Regulator Heat Sink Removal To remove the regulator heat sink (Figure 4-5) proceed follows:

as

plastic mounting piece hugs the CRT neck

to

tightly and must be spread CRT socket.

pass over the

1.

Remove the 7007165. See Paragraph 4.3.2 for instructions.

2.

Remove the four heat sink mounting screws on the right chassis wall (when viewed from front).

Lift

3.

4.

4.3.4 Yoke and CRT Removal To remove the yoke proceed

1.

2.

the heat sink assembly straight out.

To

remove a faulty transistor(s), unscrew the two 6-32 screws holding the transistor(s) down; then pun the transistor(s) straight socket. Apply an even coat (approximately

1/32 inch thick) mating surfaces the new transistor, ensuring that the base and emitter pins are oriented properly; otherwise, the transistor screw holes. Also, ensure that the insulating washer sink and that each mounting screw has a star washer.

Remove the line cord and all the circuit modules (G838/G840, A225, W682/W684) along with the plastic

Carefully remove the yoke cable connector from its mating connector on the inner side the circuit board mounting bracket.

is

of

case

between the transistor and the heat

as

out from the

of

thermal compound to

the

new

transistor. Rep]ace

will not

follows:

CRT

socket cover.

align

with the two

all

of

To remove the

Remove the yoke first,

1.

double check that the line cord

With a long-bladed screwdriver that

2.

to driver blade and chassis plus a second clip lead for safety the rubber cup on the high voltage connection at the discharge any remaining same time, remove the high voltage connection.

The connection

each have a bend or hook on the end. The connection at the these two wires together CRT metallic hole. Then those two wires are let go the CRT with the hooked ends. The connection is together and, at the same time,

out

Remove the

3.

top and bottom screws from the front bezel casting.

The

4.

corner support the weight

CRT proceed

the chassis (a clip lead between the screw-

CRT and touch the anode connection to

so

they can expand and grab the inner lip

removed by squeezing the

so

that the wires can

CRT

of

as

fol1ows:

as

described above, and

is

removed.

is

grounded

is

adequate), slide the blade under

high voltage. At the

is

made by two stiff wires that

CRT

is

made by squeezing

so

they can fit in the

"hook

dear

the anode hole.

CRT plastic mask by removing the

is

held by four screws, one at each

the screen.

As

of

the CRT.

each screw

pu11ing

is

removed,

wires"

them

of

3.

Using a screwdriver, loosen the screw that holds the yoke neck through the access slot provided shield. Loosen sufficiently for the yoke clamp to be slipped

4.

Careful1y remove the CRT socket connector

and slide the yoke clamp

5.

Slip the yoke connector through the access slot in

the CRT shield and pass it, along with the

entire yoke assemb]y,

damp

off

the yoke.

by inserting the nut driver

off

out the rear. Sometimes the yoke gets stuck at

the socket end

of

the CRT because the yoke

in

the CRT

off

the CRT neck.

the CRT neck and

4-9

CAUTION The CRT potentially in danger subjected to sharp blows or very rough handling. Also, to avoid dropping the CRT accidentally, never place your hand over the anode high voltage

picking up or carrying the CRT, in case the CRT has residual charge. The shock not, in itself, dangerous but the surprise may cause the user Never hold the CRT by the neck (the thin cylindrical portion) alone since it will break off.

is

under high vacuum and

of

implosion

button

to

drop the CRT.

is

if

while

is

a.

Remove the 7007165

as

shown in Figure unscrew the four 6-32 heat sink mounting screws from the side chassis. Remove two pin connector from the high voltage bracket.

44

and

b. Lift heat sink straight out and repair faulty transistor.

NOTE

Thermal cutouts have line voltage

sure line cord

Figure

is

removed

4-5

Regulator Heat Sink Removal

4-10

on

them - be

The VR14 CRT has a shell bond frame by which

directly fastened. The VR17 CRT bracket by four

mounted

to

damp

tubes (DEC part no. 7411301)

the CRT by a worm gear

is

fastened to its support

damp

(DEC part no.

9009555). The clamp tubes and worm gear

damp

it

are reused when replacing the VR17 CRT. When installing a new CRT

CRT using the worm gear leave sufficient slack aligned with the support bracket screw holes. clamp tubes are aligned, and the CRT fastened

on

the VR17, mount the 4 clamp tubes to the

damp.

Do not tighten fully,

so

that the

damp

tubes may be

Once the

to

but

the

support bracket, tighten the worm gear clamp.

is

4.3.S High Voltage To remove the high voltage supply proceed

1.

Remove the yoke and CRT Paragraph 4.3.4. Ensure

Supply Removal

as

that

the line cord

follows:

outlined in

is

unplugged.

2. Disconnect the two red and two white wires from the high TB2

of

the right side chassis.

vo1tage

supply from TBI and

3. Remove the cast bezel by removing the three right and left retaining screws.

4.

Remove the two side and two vo1tage remove the high

the front

assembly mounting bracket screws and

of

the unit.

vo1tage

assembly out toward

bottom

high

4-11

CHAPTER

5

Each

VR14/VR17 engineering drawings. schematics in this manual, and those delivered with the unit,

the set considered drawings shipped with the

Drawing Directory Engineering Specification Block Schematic Module Utilization

Module Utilization Circuit Schematic (G836) Circuit Schematic (G840)

Circuit Schematic (G838)

Circuit Schematic (PL)

Circuit Schematic (A22S)

Circuit Schematic (W684) Circuit Schematic (W682) Circuit Schematic (PL) Cable

Keybd. Interlock Circuit Schematic (Heat Sink) Circuit Circuit Schematic (Power Supply)

VR14 Display Assy VR14 Wired Assy Wired Assy Top

Mtg Assy

Top

Mtg Assy (PL)

CRT Yoke

Pen Assy

Light

VR14

of

the

Schematic (Deflection)

Display Assy (PL)

(PL)

Assy

Accessory List

is

shipped with a current set

If

any

discrepancies exist between

drawings shipped with the unit should be

most

accurate. Tables

VR14

Engineering Drawings

Title

VR14

Table

5-1

S-1

and

S-2

and

VR17,

B-DD-VR14-O A-SP-VR14-04 D-IC-VR14-O-1

C-MU-VR14-O-3

A-PL-VR14-O-3 D-CS-G836-O-1 D-CS-G840-O-1 B-CS-G838-0-1 A-PL-G838-0-O D-CS-A22S D-CS-W684-O-1

B-CS-W682-O-1 A-PL-W682-O-0 C-IA-7009248-O-O C-CS-7007080-O-1 C-CS-7007082-O-1

D-CS-7007084-0-1

D-UA-VR14-O-O

A-PL-

D-AD-7007078-0-O A-PL-7007078-0-O

D-AD-7007077-0-O

A-PL-7007077-O-O

D-IA -7007088-0-0 C-UA-37S-0-0

A-AL-VR14-0-7

respectively.

Drawing No.

VR14-O-O

list

-0-1

of

the

~he

ENGINEERING

Table 5-2

VR1'

Engineering Drawings

Title

Drawing Directory Engineering Specification

Block Schematic Module Utilization Module Utilization Circuit Schematic (G836) Circuit Schematic (G840) Circuit Schematic (A22S) Circuit Schematic (W684) Cable Keybd. Interlock Circuit Schematic (Heat Sink) Circuit

Schematic (Deflection)

Circuit Schematic (Power Supply)

VR17

Display Assy

VR17

Display Assy (PL)

Wired Assy

Wired Assy Top Top

CRT Light VR17

(PL) Mtg Assy Mtg Assy (PL)

Yoke

Assy

Pen Assy

Accessory List

DRAWINGS

Drawing No.

B-DD-VR17-0 A-SP-VR17-04 D-IC-

VR14-O-1 C-MU-VR14-O-3 A-PL-VR14-O-3 D-CS-G836-O-1 D-CS-G840-O-1 D-CS-A22S-0-1 D-CS-W684-O-1 C-IA -7009248-0-0 C-CS-7007080-O-1 C-CS-7007082-0-1 D-CS-7007084-O-1 D-UA-VR17-0-O A-PL-VR17-O-O D-AD-7007078-O-O A-PL-7007078-O-O D-AD-7007077 A-PL-7007077-0-0 D-IA-7007088-O-O C-UA-37S-O-O A-AL-VR17-O-6

-0-0

S-l

APPENDIX

A

NOTE

The power regulator heat sink contains a

to

thennal cutout connected voltage. Always remove the line cord before handling the heat sink.

Generally, the regulator transistors has shorted. The +22 V trolled by the transistors on the regulator heat sink (as viewed from the front NPNs sink. not corrected, the G836 board itself

if

the ±22 V reads above

PNPs

(2N4399) that are the front set

of

the

VRI4/VRI7).

(2NS302) on the rear section

If, after replacing the power transistors, the problem

The

the input line

±2S

-22 V is of

V, one or

controlled by the

the regulator heat

is

suspect.

both

is

con-

If

of

is

the

POWER

SUPPLY

TROUBLESHOOTING

regulator circuits are not working, the output could be beyond its nominal value. The MCl709 suspect, followed by the drive transistors, QI for

-22

V.

If, on the other hand, the ±22 V read zero, the same power transistors are still suspect (they may be open). Also, case,

if

the two IN4001 diodes used the power transistors are shorted, the power transistors cannot receive base current and thus rendering their output

off

turn at RXI across DIS and

and

lead connected either way should always be above S n.

the power and measure resistance with a

Dl4

if

the

-22 V was

0 V. To check for this condition,

Dl6

if

the +22 V

O.

The resistance with the

is

the most likely

Q3

for +22

as

current limiting for

will

not turn on,

YOM

was

0,

and D13

Vand

in

this

set

YOM

A-I

APPENDIX

B

When the deflection circuit cards (A225) are removed, their respective power transistors receive no drive and, therefore, are off. and observed. Any voltage at these points indicates a power transistor To determine which transistor A02-A or A03-A, has voltage. The A02-A (X-axis) transistors are on the right side viewed from the front transistors are on the left side. In both cases, a plus voltage at These are the lower transistors on both sides.

When

monitoring A02-A (X-yoke current sample)

A03-A (Y -yoke current sample) no reading should be

is

on by itself. Generally this transistor

of

the VR14/VRI7; A03-A (Y-axis)

A02-A or A03-A means the

is

faulty, observe which pin,

the heat sink assembly when

PNPs

(2N4399) are at fault.

is

shorted.

If

the voltage

DEFLECTION

AMPLIFIER

TROUBLESHOOTING

at A02-A or A03-A faulty. These are the upper transistors on both sides.

If

no readings are observed at A02-A or A03-A when the A225 boards are removed, then the deflection fault the boards themselves (assuming, signals are applied and all power supply voltages are nominal). the A225 card suspect check can be made by swapping the boards (A225) board

If

the yoke current

is

the 2N2904A, Q2.

in

question.

is

minus, the

goes

is

plugged into that axis, the most likely

If

to

see

if

the faulty

NPNs

(2N5302) are

of

course, proper input

full negative only when

one axis

is

faulty, a quick

X-

and Y -deflection

axis

follows the circuit

is

on

B-1

APPENDIX

C

After

the

power supply and deflection power transistors

have been proven sound, incorrect deflection coil current

to

readings may be isolated

is

when the A225

full negative (about

A03-A for opened and should be replaced. working

(no

plugged in, the deflection current goes

Y)

and

positive current or no negative current

the A225 circuit board itself. If,

-4 V as not

measured at A02-A for X,

controllable, Q2 has probably

If

only

half

deflection

is

A225

capability) and properly, Q3 should be replaced for Q4 for no negative current. Also, check R26 and R27 for burns. These resistors overheat operated in of

time. Finally, respectively, will burn ohmmeter

to

the

power transistors are operating

if

the

fault current limit condition for any length

if

C9 or CIO become shorted, R9 or RIO,

out.

Check C9 or CIO with an

verify this

type

of

failure.

REPAIR

no

positive current and

the deflection amplifier

is

C-I

READER'S COMMENTS

V

R14/VR17

MONITOR USER'S

VR14-0P-OOS

EK-

CRT DISPLAY

MANUAL

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DEC VR14, VR17 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual