Zenith Data Systems ZVM-124 User manual

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LIMITED RIGHTS LEGEND
Contractor is Zenith Data Systems Corporation of St. Joseph,
Michigan 49085. The entire document is subject to Limited Rights
data provisions.
INITIALS
Copyright 1985 Zenith Data Systems Corporation
St. Joseph, Michigan 49085
Printed in the United
States of America

CONTENTS
Cleaning Procedures ................................................. 7.2
Description and Specifications .......................1.1
Adjustmen ts...................................................................7.2
List of Tools, Test Equipment,
Focus Adjustment ...................................................7.2
and Supplies ................................................. 1.1
B+ Voltage Adjustment ........................................7.2
Tools ............................................................................
1.1
CRT Yoke Adjustment ........................................ 7.3
Test Equipment ...................................................... 1.1 Trou bleshooting ........................................................... 7.3
Supplies ...................................................................... 1.1
Main Circuit Board Troubleshooting ........... 7.4
Specifications ............................................................. 1.2
Main Circuit Board Waveforms ...................... 7.4
CRT Socket Board Troubleshooting .............. 7.5
Installation ...................................................... 2.1
Power Supply Troubleshooting ........................7.6
V
ideo Moni tor ............................................................ 2.1
Vol tage Selection ...................................................... 2.2
Reassembly ........................................................8.1
Connections ................................................................. 2.4 Control Panel Assembly Installation ................ 8.1
Signal Cable Interface ............................................ 2.4 Power Switch Assembly Installation ................ 8.1
Main Circuit Board Installation ......................... 8.1
Operation ...........................................................3.1
Fuse Board Installation ........................................... 8.2
Initial Setup of the Operating Power Transformer Assembly Installation .... 8.3
Controls and Monitor ............................... 3.1 Ca thode- Ra y Tube Installation .......................... 8.3
CRT Socket Board Installation ...........................8.4
Theory of Operation ....................................... 4.1
Back Cover Installation .......................................... 8.4
Theory of Operation .............................................. 4.1
Video and Highlight Inputs ..............................4.1 Parts Lists ..........................................................9.1
Vertical Sync Input ............................................... 4.1
Horizontal Sync Input..........................................4.2 Figures
1.1 The ZVM-124 Video Monitor. ............... l.l
Circuit Description ...........................................5.1
2.1 Video Monitor Front View ..................... 2.1
Power Supply ............................................................... 5.1
2.2 Video Monitor Rear View ...................... 2.1
Video and Highlight 2.3 l20-Volt Wiring ..........................................2.2
Driver Circuitry .......................................... 5.1 2.4 Main Board Transformer Leads ...........2.2
Horizontal Circuitry .................................................5.2 2.5
Power Transformer Replacement ....... 2.3
Vertical Sweep Circuit ........................................... 5.3 2.6 Power Switch Replacement... .................2.3
Schematic .......................................................................5.4 2.7 220-
Volt Wiring............................................ 2.3
2.8 Monitor Cable Connections ....................2.4
Disassembly........................................................6.1
3.1 Front Panel Controls .................................3.2
Back Cover Removal ............................................... 6.1
3.2 Video Monitor Rear View ......................3.2
Power Transformer Assembly Removal ......... 6.1
4.1 ZVM-124 Block Diagram .........................4.2
Fuse Board Removal ................................................ 6.2 5.1 Schematic ........................................................ 5.3
CRT Socket Board RemovaL ..............................6.2 6.1 Back Cover Removal................................. 6.1
Main Circuit Board Removal .............................. 6.3 6.2 Transfer RemovaL .................................... 6.1
Power Switch Assembly RemovaL ................... 6.4 6.3 Transformer Disassembly ....................... 6.2
Control Panel Assembly Removal .....................6.4 6.4 Fuse Board ..................................................... 6.2
Cathode-Ray Tube Removal ................................ 6.4 6.5
Main Board .................................................... 6.2
6.6
Fuse Board Removal .................................6.3
Servicing Instruction ........................................7.1 6.7
CR T Socket Board Removal ..................6.3
Safety and Service Guidelines ............................ 7.1
6.8 Main Board Removal,
AC Leakage Test ..................................................... 7.1
Discharging the CRT ....................... 6.3
Other Precautions ................................................... 7.1 6.9 Power Switch Removal ............................6.4
Page iii

6.10 Control Panel RemovaL ......................... 6.4
Listing
6.11 Preparing the Cathode-Ray
3.1 BASIC Program Used to Fill
Tube for Removal ............................. 6.5
Screen with a Character. ................ 3.1
6.12 CRT Yoke Preparation ............................ 6.5
6.13
CRT Removal ................................................6.5
7.1 AC Leakage Test Arrangement ............ 7.1
7.2 Internal Adjustments ................................ 7.2
7.3
Yoke Adjustment ........................................ 7.3
7.4 Waveform at Base of Q601,
Vertical Oscillator .............................7.4
7.S Waveform at Emitter of Q601,
Vertical Oscillator .............................7.4
7.6
Waveform at Collector of Q601,
Vertical Oscillator .............................7.4
7.7
Waveform at Emitter of Q606,
Vertical Output .................................. 7.5
7.8 Waveform at Emitter of Q607,
Vertical Blanking ............................... 7.5
7.9 Waveform at Collector of Q501,
Horizontal Driver ...............................7.5
7.10
Waveform at Base of Q501,
Horizontal Driver ............................... 7.5
7.11 Waveform at Base of Q20S,
Video Input ...........................................7.5
7.12
Waveform at Pin 2 of VX201,
Cathode of the CRT ......................... 7.5
8.1 Control Panel Assembly
Installation ............................................. 8.1
8.2 Power Switch Assembly
Installa tion .............................................. 8.2
8.3
Main Circuit Board
Installa tion .............................................8.2
8.4
Fuse Board Installation ............................ 8.2
8.5
Power Transformer Assembly
Installa tion .............................................8.3
8.6
Installing the CRT in the
Cabinet ....................................................8.3
8.7
Yoke Leads .................................................... 8.3
8.8
CRT Socket and
High Voltage Anode Lead ............. 8.4
8.9
CRT Socket Installation .......................... 8.4
8.10
Back Cover Installation ........................... 8.4
9.1 Exploded View ............................................. 9.1
9.2 Component Location,
Circuit Boards ......................................9.2
Tables
2.1 Signal Cable Connector J201.. ............... 2.4
7.1 General Troubleshooting ........................ 7.3
7.2
Main Circuit Board
Trou bleshooting ..................................7.4
7.3
Power Supply Troubleshooting ............ 7.6
9.1 Major Assemblies........................................ 9.1
9.2 Component Parts List ............................... 9.2
Page iv
Contents

The Zenith Data Systems ZVM-124 Video
Monitor is fitted with signal and power cables
to interface directly with the IBM PC
computer and includes the following features.
Refer to Figure 1.1.
• Major operating controls behind an access
door on the front panel.
• A
12-inch display, featuring a non-glare,
amber phosphor CRT, capable of
displaying 25 rows of 80 characters per
row.
• A
width adjustment accessible from the
rear panel.
• Focus control and video circuits mounted
on the CRT socket board to aid in
servicing.
• A power switch with a power indicator on
the front panel.
Figure 1.1
The ZVM-124 Monitor
List of Tools, Test
Equipment, and Supplies
The following tools, test equipment, and
supplies are recommended for servicing this
product.
DESCRIPTION
AND SPECIFICATIONS
TOOLS
•
1/4" nut driver
•
Standard screwdriver, 1/4" blade
•
Phillips screwdriver, No.1 tip
•
Phillips screwdriver, No.2 tip
•
Diagonal cutters
• Wire
strippers
• Long-nose
pliers
•
Desoldering tool
•
Soldering iron, 25 to 40 watt
•
Power cord, HE-89-60
TEST EOUIPMENT
• Oscilloscope - DC to 35 MHz, triggered
sweep, with low capacitance (3 pF) probe
• Digital voltmeter - High impedance input,
zero to 1000 volts, zero to 1 megohm,
Heath model SM-2215, or equivalent
• High voltage probe - Zero to 40 KV, Heath
model IM-5210, or equivalent
• Signal source - Quantum 801 A or
equivalent in place of an IBM PC computer
SUPPLIES
• Solder, 60/40, HE-331-13
•
Desoldering braid, HE-490-185
•
Cable ties, HE-354-59
•
Lint-free cloths
Page 1.1

Specifications
Operating Voltage: 120 VAC 60 Hz
(ZVM-124);
220 VAC
50 Hz
(ZVM-124-E)
Operating Current: 0.3 ampere
Nominal Power: 28 watts
Nom. High Voltage: 13.0 KV
Fuse (primary):
Fuse (secondary):
Video
Bandwidth:
Rise Time:
Horiz.
Frequency:
Vert. Frequency:
Input Signal:
CRT:
Character Type:
Characters/Line:
Character Block:
Page 1.2
4.0 amp,
type FX320I
2.25 amp,
type FX70 I
18 MHz
20 nanoseconds
18.432
KHz
50.09 Hz
Four TTL-level inputs
12" diagonal, amber
8 x 10-pixel matrix
80 characters per line
7 x 9 pixels
Description and Specifications

The Zenith Data Systems ZVM-124 Video
Monitor is a self -contained unit and is
designed to be connected to an associated
computer using an attached shielded signal
cable and power cord. The monitor receives
four TTL-level video signals (video input,
highlight input, vertical input, and horizontal
sync input) via the signal cable and D-type
connector and 120 VAC (or 220 VAC on the
ZVM-124-E) power via the power cable and
connector.
The monitor must be located in an area that
will provide proper ventilation. There are
vents on the back and bottom of the cabinet
which permit air flow through the monitor.
Verify that these vents are not blocked.
Video Monitor
The following is a description of the controls
and cables for the video monitor. Refer to
Figure 2.1, position the video monitor so the
front of it is facing you, and open the front
door as shown.
• Contrast - The CaNT. control adjusts the
intensity of the displayed data on the
screen.
•
Black Level - The BLACK LEVEL control
adjusts the intensity of the raster
(background ).
• Vertical Size - The VERT. SIZE control
adjusts the vertical size at the top and the
bottom of video display.
• Vertical Hold - The VERT. HOLD control
adjusts the vertical sweep for a stable
display.
• Horizontal Hold - The HORIZ HOLD
control adjusts the horizontal sweep for a
stable display.
• Power Switch - This push-to-latch, push-to-
release switch turns the monitor on or off.
INSTALLATION
• Power Indicator - This LED lights when
power is applied to the monitor and the
power switch is turned on.
CONT
INDICATOR
POWER
V SWITCH
ERT SIZE HORIZ HOLD
VERT HOLD
Figure 2.1
Video Monitor Front View
Refer to Figure 2.2 and position the video
monitor so the back is facing you.
•
Power Cord - This grounded, AC power
cable connects to the 120-volt (for the
ZVM-124) AC output of the computer, or
with the HE-89-60 power cord, to any
standard (120 VAC) AC power source. (The
ZVM-124-E monitor accepts 220 VAC
through this cord.)
•
Signal Cable - his shielded cable connects
to the output of the monochrome video card
of a computer.
• Width Control - This control adjusts the
horizontal size of the video display.
10
ft.4.-4I!+---t-tr WID TH
CONTROL
o
POWERf ~'J.r.r.r.rrrr.r.rrrr.r,
COR~} SIGNAL
(/ CABLE
a ~
~ii
Figure 2:2
Video Monitor Rear View
Page 2.1

Voltage Selection
Before connecting the monitor to a power
source, make sure it is rated for the voltage
available in your area. The ZVM-124 monitor
is normally wired for 120 volts AC. To change
the voltage rating to 220 volts AC, proceed as
follows:
WARNING: Be
sure the signal cable and power
cord are unplugged from the computer or any
other signal and power source before you
att,empt to change the voltage rating of this
unit.
1. Refer to Section 6, "Detailed
Disassembly," and remove the back cover,
power transformer assembly, fuse board,
main board, and power switch assembly.
2. Refer to Figure 2.3 and unsolder the two
pairs of the l20-volt transformer leads at
A, B, C, and D on the fuse board. (These
leads are normally a pair of light tan (or
white) and a pair of gray leads. One lead
of each pair will normally have a brown
stripe.)
3. Unsolder the two l20-volt power line
leads at G and H on the fuse board.
4. Unsolder the 120-volt power switch (S201
- part number 85-1559) leads at I and J
on the fuse board.
•
, 204-11.7:~C;~
G CX208 U3:eN
• 221)'"
C GIII".lU
II ".,. Tel .......
"... ..v.o B
• ex 209
.
r;s
"o~. :~.'
TRANSFORMER GROUND BLACK
120V WHITE/BROWN (NOT REMOVED)
Figure 2.3
120-Volt Wiring
5. Refer to Figure 2.4 and unsolder the two
120-volt transformer leads at E and F on
the main circuit board. Note how these
Page 2.2
leads are routed in relation to the other
wiring.
Figure 2.4
Main Board Transformer Leads
6. Refer to Figure 2.5 and remove the two
6-20 x .312" screws that hold the
transformer cover in place. Remove the
cover.
7. Remove the two 8-18 x 1.25" screws that
hold the l20-volt transformer to the
power transformer frame. Note how the
leads are routed out of this assembly
8. Replace the l20-volt power transformer
(TX201 - part number 95-3388-04) with a
220-volt transformer (part number 95-
3578-03).
9. Replace the two 8-18 x 1.25" screws that
hold the transf ormer to the power
transformer frame and tighten them.
10. Route the leads of the transformer as
they were for the 120-volt transformer
and use the two 6-20 x .312" screws to
replace the transformer cover. Tighten
the screws.
11.
Refer to Figure 2.6 and remove the two
8-18 x .437" screws at F. Remove and
replace the l20-volt power switch with-a-
220-volt power switch (part number 85-
1646).
Replace the two screws at F.
Installation

12. Refer back to Figure 2.4 and solder the
red and brown transformer leads to E and
F on the main board.
Figure 2.5
Power Transformer Replacement
Figure 2.6
Power Switch Replacement
Installation
13. Refer to Figure 2.7 and solder the two
220-volt transformer leads at A (the gray-
brown lead) and J (the gray lead) on the
fuse board.
14. Solder the power line leads at I (the
brown lead) and L (the blue lead) on the
fuse board.
15. Solder the SX201A power switch leads at
B (the gray/brown lead) and M (the
gray /blue lead) on the fuse board.
16. Solder the SX201B power switch leads at
N (the brown/gray lead) and C (the
brown lead) on the fuse board.
17. Refer to Figure 2.7 and remove and
replace the 4 amp fuse at K on the fuse
board (FX201 - part number 136-114-23)
with a .160 amp fuse (part number 136-
133-07).
Figure 2.7
220-Volt Wiring
220V LINE
18. Refer to Section 8, "Reassembly," and
replace the power switch assembly, main
board, fuse board and power transformer
assembly, and back cover. Verify that all
the power and signal leads are routed as
shown in the figures in that section.
NOTE: The ZVM-124-E monitor is wired for
220 volts AC at the factory. To change the
voltage rating to 120 volts AC, follow the
same procedure, but substitute the 120-volt
parts (95-3388-04, 85-1559, and 136-114-23) for
the equivalent 220-volt parts in the
instructions.
Page 2.3

Connections
To install and connect the monitor, refer to
Figure 2.8 and complete the following
procedure.
1. Place the monitor on a solid work surface
near the computer.
2. Rotate the video monitor until the front
is facing you.
3. Make sure the power switch on the front
of the cabinet is off; also check that the
power switch on the computer is off:
4. Plug the shielded signal cable into the
appropriate video connector on the rear
panel of the computer.
5. Plug the power cord into the power
connector on the rear panel of the
computer.
6. Turn the power on.
Signal Cable Interface
The monitor is designed to be used as a
display device for a computer system. The
shielded cable is used to connect the monitor
to the computer.
CAUTION: A shielded cable is required by
FCC regulations to prevent interference with
other equipment.
Table 2.1 provides information on the signal
cable at the D-type connector.
Table 2.1
Signal Cable Connector J201
PIN
NUMBER SIGNAL FUNCTION
1 Shield ground
2 Signal ground
3 Not used - not connected
4 Not used - not connected
5 Not used - not connected
6 Highlight input
7 Video input
8 Horizontal sync input
9 Vertical input
ZVM-124 MONITOR
tt rrt E: t rcttlC"LtttttEltLLLcLctttLL
POWER
CORD
o
.r'J'J'Jrrr'J'Jrrrr
SIGNAL
CABLE ~--...I
11111111111111111 11111111111111
Figure 2.8
Monitor Cable Connections
Page 2.4 Installation

This monitor uses the latest in solid-state
technology for displaying video signals. The
four TTL-level video signals (video input,
highlight input, vertical input, and horizontal
sync input) are received from the computer
via the signal cable. This section covers the
initial setup of the operating controls.
Initial Setup of the Operating
Controls and Monitor
The following discussion assumes that you will
be
connecting the monitor to a computer, such
as the IBM PC. Since the monitor requires
TTL-level signals to drive it, the normal
composite signals of the Zenith Data Systems
Z-100
and Z-100 PC computers cannot be used
as a
signal source. However, in lieu of a
computer, you may use a Quantum 801 A or a
similar signal source to make your
adjustments.
The location and function of each control is
discussed in Section 2, "Installation."
l. Connect the ZVM-124 to a suitable signal
source, such as an IBM PC.
The power switch is located on the front of
the cabinet and turns the monitor on or off.
The operating controls are located behind a
door below the CRT screen in the front of the
cabinet and on the back cover.
2. Turn on the computer (or test equipment)
to which the ZVM-124 is connected.
3. Locate the power switch on the monitor
and press it to turn it on. Verify that the
power indicator, an LED, lights.
4. Assuming you are using a computer, use
the BASIC program shown in Listing 3.1
to fill the screen with any character as
follows:
a.
Enter the program shown in Listing
3.1 into the computer. You may want
OPERATION
to save this program on a disk for
later use.
b. Run the program by typing RUN and
pressing the RETURN key. The
screen will be filled with the letter
Z or any other character inserted in
line 20.
c.
To end the program, press the CTRL
and BREAK keys at the same time.
Listing 3.1
BASIC Program Used to Fill Screen
with a Character
10 FOR 1=1 TO 2000
20
PRINT "Z"j
30 NEXT I
40
GOTO 40
'replace .the "Z" with the
'character of your choice
With the monitor connected to a computer (or
other signal source) and with a normal video
display on the CRT screen, adjust the front
panel controls. Refer to Figure 3.1 for the
location of the controls during the following
discussion.
l. Adjust the black level control, labeled
BLACK LEVEL, counter-clockwise until
the sweep raster is visible on the screen;
then back off the control until the raster
just disappears. Note that this control
interacts with the contrast control.
2. Adjust the contrast control, labeled
CONT., until the video display is
comfortable to the eye. Note that this
control interacts with the black level
control.
3. Adjust the horizontal hold control,
labeled HORIZ HOLD, as required for a
stable horizontal display on the screen.
4. Adjust the vertical hold control, labeled
VERT. HOLD, as required for a stable
vertical display on the screen. Note that
this control interacts with the vertical
size control.
Page 3.1