Zenith Data Systems SM-ZVM-134 User manual

Copyright © 1983
Zenith Data Systems
All Rights Reserved
SM-ZVM-134
Color Monitor
ServiceManual
SAINT JOSEPH, MICHIGAN 49085
585-23
First Printing
Printed
in the United States of America

II
•
•
•
•
•
CAUTIONS ... WARNINGS
When you are servicing the ZVM-134 Moni-
tor,
under no circumstances should you alter
or modify its design without permission from
ZenithData System.
Replace all components with the original
parts listed
in Replacement Parts List in this
Manual.
The
CRT uses integral implosion protection.
The yoke is permanently bonded to
the CRT.
Do not attempt to separate the yoke from the
neckof the
CRT.
NOTE: Reference to Hot Ground and Cold
Ground are madethroughout thetext.
Hot Ground is an AC hot ground. It is taken
from the metal plate located
on the right side
of the monitor that holds the sweep assembly
together.
Cold Ground is a DC cold ground. It is taken
from the
main chassis across the top of the
monitor.
•
•
Discharge the high voltage lead going to the
anode of the
CRT. One method of discharging
it is to use a screwdriver
and a 12" jumper
wire with an alligator clip on each end. Clip
one alligator clip to the chassis
or to the DAG
connector on the CRT, and place the otherone
on your screwdriver. Then slide the end of
the screwdriver
under the high voltage cap
at the anode of the
CRT. Refer to the illustra-
tion below.
We recommend that you use an isolation
transformer
when you are working on this
Monitor.
Illustration 1
High Voltage lead discharge

III
Table of Contents
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . .. 1-1
SPECIFICATIONS
.... . . . . . . . . . . . . . . . . . . .. 2-1
INSTALLATION AND START UP
.......... 3-1
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-1
Cable Description ........................ 3-1
Cable Connection . . . . . . . . . . . . . . . . . . . . . .
.. 3-3
GreenIWhite Switch . . . . . . . . . . . . . . . . . . . .
.. 3-3
On-Off Switch . . . . . . . . . . . . . . . . . . . . . . . . .
.. 3-4
THEORY OF OPERATION
................ 4-1
Input Voltage ........................... 4-1
Degaussing Coil
......................... 4-1
Horizontal
Output Transistor .............. 4-1
Modules
................................ 4-2
Main Board
........................... 4-2
Sweep Assembly . . . . . . . . . . . . . . . . . . . . .
.. 4-2
Video
Output Board . . . . . . . . . . . . . . . . . . .. 4-2
RGB Input Signal . . . . . . . . . . . . . . . . . . . . . . .. 4-2
DISASSEMBLY
.......................... 5-1
Back Cover ............................. 5-1
Video Output Board . . . . . . . . . . . . . . . . . . . . .. 5-2
Main Board . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 5-3
Sweep Module
and High Voltage Section ... 5-4
CRT
................................... 5-6
On-Off
Switch. . . . . . . . . . . . . . . . . . . . . . . . . .. 5-8
SERVICE PROCEDURES .................. 6-1
Quick Checks
........................... 6-1
Conditions Symptoms
and Checks ......... 6-2
Adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-3
Measurements
.......................... 6-16
REPLACEMENT PARTS LIST
.............. 7-1
Exploded View . . . . . . . . . . . . . . . . . . . . . . . . .. 7-1
Horizontal Width Sweep Assembly ......... 7-3
Main Board . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 7-4
CIRCUIT BOARD X-RAYS VIEWS
........................ fold-out from 8-1
SCHEMATIC DIAGRAMS
.............. fold-in

IV

Introduction
The ZVM-134 is a high resolution Color Monitor
which accepts direct RGB video inputs, displays
twenty-five 80-character lines, has
20 MHz
bandwidth and 20 ns rise time, and uses modular
chassis designfor ease of service.
This Monitor is certified to comply
with the limits
for a class B computing device
pursuant to subpart
Jofpart 15 of the FCC rules.
Service of
the ZVM-134 is to board level. When you
determine that a circuit board is at fault, it
must
be replaced. Return the defective board to your Ze-
nith Data Systems Distributor.
Page 1-1
Tools and test equipment required for servicing the
ZVM-134 monitor:
•
1/4" nut driver
•
1/4" long shank nut driver
• 1/4"flat screwdriver
• Needle-nose pliers
• Digital voltmeter
• Oscilloscope
• Isolation transformer
• Software-ZDOS
with VMEMTEST
• ZBASIC

Page 1-2

Specifications
Operating Voltage .......................... .
Operating Current
.......................... .
Normal Power
............................. .
Nominal High Voltage
...................... .
Fuse Protection
............................ .
Input
..................................... .
CRT ..................................... .
Pixel Display
.............................. .
ColorlMonochrome Display
.................. .
Size
...................................... .
Page
2-1
120 V AC 60 Hz.
"E" version: 240 VAC, 50 Hz.
.87 Amps maximum.
69 Watts.
33kV.
4 Amp, type FX3201.
DB-15 type connector.
RGB signals-TTL positive (Analog, 0-5 V).
Composite sync -TTL positive or negative (Analog,
1-5 V).
Horiz sync -TTL positive or negative (Analog,
1-5 V).
Vert sync - TTL Positive or negative (Analog,
1-5 V).
Ground.
13",90 degree, .43
mm fine pitch dot mask.
26 kV
at 0 beam.
450jJ.A max beam current.
100 voltcutoff.
Internalmagnetic
shield .
.7
mm maxconvergence error.
Sealed systemtube, yoke, beam-bender.
640 x 250.
GreenlWhite switch.
13.5"H x 20"W x 15"D
Zenith Data Systems reserves the right to discon-
tinue products
and to change specifications at any
time
without incurring any obligation to incorporate
new features in products previouslysold.

Page 2-2

Page 3-1
Installation and Start Up
LOCATION
The ZVM-134 Monitor should be located near an
AC power source, and in an arfla which will provide
proper ventilation. There are vents on the bottom,
back, and top of the cabinet
which permit air to flow
through the cabinet, keeping the components cool.
Be sure these vents are notblocked.
CABLE DESCRIPTION
The following two RGB cables are available for the
ZVM-134 Monitor.
CABLE
ZVM-134-1
ZVM-134-Z
ZVM-134-3
COMPUTER
Z-100 family ofcomputers
IBM
Apple
CAPt./!- /I
-z,VII"'/1¥-/
PIN SIGNAL 'I
Plr( T~ J"1JI8IJ
1
-H
8
2
+H
3 not used
4
+V
'I- 2. 4 OJ/.~""
5 G To
6 B 5 z0
().J7- G It J)
7 R 3
:Z () I) J(.,
8 not used
9
-V
9
10 not used
11 GND
2.
12 not used
13
not used
14
not used
15
not used
.j"HEi.C.-(SHI6I.ijJ----- S/f1Z tL
NOTE: Composite sync can be used. However, nega-
tive composite sync
must be applied to both pins
1
and 9, or positive composite sync must be applied
to both pins 2
and 4. This will require a modified
cable.
The connectorpinout for the
RGB cable is as follows. ~ ~
Refer to Figure 3-1. ~ ~ \l ~ ~ ~ ~ ~ \\ \\ \\ \\
Figure3-1
Connector pinout
I !j
,-~.-
FROM COMPUTER
t..o==='" .•

Page 3-1
Installation and Start Up
LOCATION
The ZVM-134 Monitor should be located near an
AC power source, and in an area which will provide
proper ventilation. There are vents
on the bottom,
back,
and top of the cabinet which permit air to flow
through the cabinet, keeping the components cool.
Be sure these vents are not blocked.
CABLE DESCRIPTION
The following two RGB cables are available for the
ZVM-134 Monitor.
CABLE
ZVM-134-1
ZVM-134-2
ZVM-134-3
COMPUTER
Z-100 family ofcomputers
IBM
Apple
PIN SIGNAL
1 -H
2 +H
3 not used
4 +V
..... f\'M.o- 5 G
.............. - 6 B
R
not used
9 -V
10 not used
Z6tf IrH CA".e 1:/
7-(11'13,-21
Fo~ V.cp IJ/"f .IBn PC
9iJiff 0 TfJ.,t'Bi/
,
9
~
--11 GND 2-
12 notused
13
not used
14 not used
~ ;'\
15 not used , {£", ft-", "" IIfS1'NU"J
.rtlGt~ (S"/I&,(.IJ SHetl
NOTE: Composite sync can be used. However, nega-
tive composite sync must be applied to both
pins
1 and 9, or positive composite sync must be applied
to both pins 2
and 4. This will require a modified
cable.
The connector pinoutfor the
RGB cable is as follows. \\ \\
Refer to Figure 3-1. ~ ~ ~ \\ \\ \\\\ \\\\ \\ \\ \\
Figure 3·1
Connector pinout
I
'I
,- ....
FROM COM PUTER
'-="'~"-

Page 3-2
CABLE CONNECTION
Refer to Figure 3-2 and connect your RGB cable to
}9, located at the rear of the Z-100 Computer. Con-
nect the other
end of the RGB cable to the back of
the ZVM-134 Monitor.
GREENIWIDTE SWITCH
Position the rear panel GreenIWhite switch to White
if you want a color display, or to GREEN if you want
a monochrome (green) display. Refer to Figure 3-2.
ON·OFF SWITCH
With the Monitor plugged into a power source and
the RGB cable properly connected, turn the On-Off
switch, located on the front panel, clockwise to the
Onposition.
Figure 3·2
Cable connection

Theory of Operation
Refer to the fold-in schematic diagrams when read-
ing the following section.
INPUT VOLTAGE
The input line voltage enters the main module at
connector 3R8, where
it goes through a line fuse and
an LCI (line-conducted interference) choke. The LCI
prevents monitor-generated noises from feeding
backinto
the AC line.
Line voltage is applied across the bridge rectifier,
which is referenced to
hot (AC) ground. Hot ground
is considered as
the hot part of the chassis. (Use
an isolation transformer when you are working on
this Monitor.) The output of the bridge rectifier then
goes through a pie-type filter, where it supplies
power to various circuits.
DEGAUSSING COIL
Any external magnetic force may magnetize the
mask of
the CRT. Therefore, it becomes necessary
to degauss the
CRT every time the Monitor is turned
on. The CRT is degaussed by the line voltage which
is applied to a coil wrapped around the the tube.
The degaussing circuit includes thermistor R3245,
which is located across
the AC line. Due to the posi-
tive temperature coefficient
on the thermistor, its re-
sistance is very low
when the Monitor is off. When
the Monitor is
turned on and current begins to flow
through
the thermistor, the thermistor heats up, and
Page 4-1
its resistance increases to several megohms. This in-
creased resistance decreases the current through
diodes CR3210
and CR3211, which causes the de-
gaussing coil to become inactive.
HORIZONTAL OUTPUT TRANSISTOR
When the Monitor is turned on, the first voltage to
come
up in the sweep module is the 150 VDC sup-
ply. This is
the B+ voltage for the H.D.T. (horizontal
outputtransistor).
In order for
the power supply system to work, the
horizontal oscillator must be running so that it can
drive the H.D.T. and other voltage pulses from the
sweep assembly.
Transformer T3201
on the main board provides the
26 VAC SU and 12 VAC SU (SU=start up) voltages
necessary to start the oscillator running. At start up,
these voltages are closer to 12-15 VAC and 6-8 VAC
respectively.
These voltages are applied to various points
on the
sync processor chip to start the horizontal drive os-
cillator running.
When the oscillator is running, the
horizontal drive output is generated. You can mea-
sure this
output drive at pin 5 of sync processor
IC3401, located on the main board.
When you are taking measurements from
the various
supplies, we recommend that you sync-lock
the
Monitor to a signal source.

Page 4-2
MODULES
The ZVM-134 consists of three primary modules
havingvarious sub-assemblies:
• Mainboard
• Video
output board
• Sweep assembly
MainBoard
The main board's primary function is to generate
horizontal
and vertical drive outputs for the scan
signals.
All sync processing uses the sync processor
IC
(#221-264). This processor contains horizontal and
vertical oscillators, horizontal and vertical output
drivers, horizontal APC, and accepts positive or
negative horizontal
and vertical sync.
The vertical output is
on pin 14 and drives a stacked
pair of transistors for vertical scan generation. The
vertical
output also goes to connector 3G3 on the
mainboard
which is fed to thesweep assembly.
The horizontal
output on pin 5 drives the horizontal
output transistor. The horizontal output also goes
to connector 3G3 on the main board, and is then
fed to thesweep assembly.
There are two grounds to be considered,
hot ground
(AC), and cold ground (DC). AC hot ground is refer-
enced to the low side of the line. The potential
on
AC ground may be rather large relative to earth
ground.
DC ground is isolatedthrough the horizontal
drivertransformer.
Sweep Assembly
The high voltage is generated by the sweep trans-
former, which is driven by the horizontal
output
transformer. The sweep transformer also has several
pulse windings
on it. These secondary windings
generate different pulse amplitudes thatare fed back
to the main module, where they are rectified and
filtered to provide supply voltages. The transformer
is also tapped to provide
G2 and focus voltage for
the
CRT.
Video Output
The video output board is located on the neck of
the
CRT. This board consist of the video output driv-
ers that drive the
CRT.
RGB INPUT SIGNAL
The RGB input signals enter the Monitor through
a
DB-15 connector located at the rear of the unit.
Next to this connector is a two-position slide switch
that is labled GreenlWhite. When the switch is
in
the Green position, the red and blue signals are dis-
abled for monochrome (green) display. When the
switch is
in the White position, all red, green, and
blue signals willbe displayed.

Disassembly
BACK COVER (Referto Figure 5-1.)
The back cover is secured to main chassis
with six
screws across the rear of the cabinet. To remove the
backcover:
• Remove the power cord from the power
source.
~
[ [[[[[[[[[
•
•
•
•
•
Figure 5-1
Back coverremoval
Page 5-1
Disconnectthe RGB cable.
Remove the two short hex screws near
the top
(A).
Remove the three long hex screws near
the bottom
(B).
Remove the one short hex screw next to
the
RGB IN connector (C).
Remove theback cover.

Page 5-2
VIDEO
OUTPUT
BOARD
(Refer to Figure 5-2.)
The video
output
board
is connected to
the
CRT
by
the
socket connector.
To remove
the
driverboard:
• Remove thebackcover.
• Carefully remove
the
board
from the
CRT
neck.
VIDEO
OUTPUT
BOARD
•
•
•
•
Remove cable 5A2 from the video
output
board.
Remove cable
5C2
from
the
video
output
board.
Disconnect
the
focus voltage
lead
by
twisting
the
two plastic
leads
about
1/8
turn,
and
then
pulling
them
apart.
Disconnect the gray grounding
wire
that
goes to
the
grounding strap
on
the
CRT.
GRAY
GROUNDING
WIRE
Figure
5-2
Video
output
board
removal

MAINBOARD (Refer to Figure 5-3.)
The main board is fastened to the chassis with two
screws, four plastic tabs,
and two plastic pins. To
remove the
main board:
•
•
•
•
•
•
•
•
Remove theback cover.
Remove screws A
and B.
Remove cables at 2A5, 2B5, and 3F3 on
the main board.
Remove cables at 3T8, 3S8,
and 3R8.
Remove cables at D
and E.
Remove cables at 3D3 and 3G3.
Remove cables at 3W3
and 3V3.
Pull
out on the two tabs (X,X) in front
and lift the board until it passes the
notch on the tabs.
•
•
•
Page 5-3
Pull out on the two tabs on the sides and
lift the board until it passes the notch
on the tabs.
Free the board from
the two pins (Z), lo-
cated
on each side toward the rear, by
pulling up on theboard.
Remove the
main board.
WARNING: Due to a large
power supply
filter capacitor, there may be 150 VDC
residual voltage present at connectors
3W3
and 3V3. Use caution in this area.
dR a " c D~, __ ~
Figure 5-3
Mainboard removal

Page 5-4
SWEEP MODULE and HIGH VOLTAGE SECTION
• Remove connector 3F3 from the
main
(Refer to Figure 5-3 and 5-4.) board (green,whitelblue).
• Remove connector
5X3 from the video
The sweep module
and high voltage section are con- outputboard (whitelbrown).
tained
in one assembly. To remove this assembly: • Remove connector 5H3 from the video
outputboard (gray,brown).
• Remove the backcover. • Remove connector 3S3 from the sweep
• CAUTION -Before you
go any further, moduleboard (red,blue).
discharge the high voltage lead going to • Remove connector 2A3 from the high
the anode of the
CRT. For discharge pro- voltage board (yellow,white).
cedures, refer to the following para- • Remove the ground wire from the
CRT
graphs. groundingstrap.
• Remove hex
nut screw B.
One method of dischargingthe high volt- • Remove hex
nut screw C.
age lead is to use a screwdriver and a • Remove
hex nut screw D (a long shank
12" jumperwire with an alligator clip on
or short shank 1/4" nut driver is
each end. Connect one alligator clip to necesssary).
the chassis, or to the
DAG connector on
• Pull outthe highvoltage assembly.
the
CRT, and place the other alligator • Remove connector
3V3 from the main
clip on your screwdriver. Slide the end
board (gray,red).
of the screwdriver
under the rubber high • Remove connector 3W3 from the main
voltage cap at the anode of the CRT.
board (white,violet,yellow).
• Remove connector
3G3 from the main
You may or may not see a discharge board (white,violet,yellow,red,white/
spark depending
on how much charge yellow).
is builtup. • Remove connector
3D3 from the main
board (whitelblack, violet,white/green,
• Remove the red
and white focus voltage orange,white/violet,white,orange).
lead by twisting the two white plastic • Remove the complete high voltage as-
pieces 1/8 turn. sembly.
Figure5-4
Sweepmodule, high voltage assemblyremoval

CRT (Referto Figure 5-5.)
The CRT is fastened to the chassis with four screws
located inside the cabinet. To remove
the CRT:
• Remove the backcover.
• CAUTION -Before you
go any further,
discharge the High Voltage lead going to
the anode of the
CRT. For discharge pro-
cedures, refer to
the following para-
graphs.
One method of discharging
the highvolt-
age lead is to use a screwdriver
and a
12" jumper wire with an alligator clip on
each end. Connect one alligator clip to
the chassis, or to the DAG connector on
the CRT, and place the otherclip on your
screwdriver. Slide
the end of the screw-
driver
under the high voltage cap at the
anode of the
CRT.
You may or may not see a discharge
spark depending
on how much charge
is builtup.
Figure 5-5
CRT removal
•
•
•
•
•
•
•
•
•
Page 5-5
Remove the driver board from the neck
oftheCRT.
Remove connector 3T8 from
the main
board (red,red).
Remove connector 2A3 from
the high
voltage board (yellow,white).
Remove connector 3S3 from
the sweep
moduleboard (red,blue).
Place
the Monitor so the front is lying
face down
on a padded or protected sur-
face.
Remove hex
nut screws A,B,C.
Remove hex nut screw D (this nut will
require a long
shank nut driver).
Carefully lift
out the CRT by grasping it
on its sides. Do not lift the CRT by the
neckoryoke.
Remove the degaussing coil.

PageS-6
ON-OFF SWITCH (Refer to Figure 5-6.)
The On-Off switch is fastened to a bracket which
is mounted to the inside front chassis. To remove
the On-Off switch:
• Remove the backcover.
• Pull the switch knob off from the front
ofthe cabinet.
• Remove the hex
nut screws (X) from the
switchmountingbracket.
• Remove the large hex
nut holding the
switchto the bracket.
Figure 5-6
On-Off switchremoval
o

Page 6-1
Service Procedures
QUICK CHECKS
Make the following preliminary checks to confirm
the operatingconditionof the Monitor.
•
•
Check all connectors for good connec-
tions.
Check the GreenIWhite switch position.
Refer to Page 3-2.
•
•
•
Check the RGB connectorfor a good con-
nection. Refer to Page 3-2.
Check the
CRT filament for filament
light.
When power is applied, check for high
voltage static
on the face of the CRT by
rubbingyour hand on the screen.