Tatung VM-14AF User manual

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VM-14AF
SERVICE MANUAL

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CONTENTS
1 SPECIFICATION
2 OPERATING INSTRUCTIONS
3 IMPORTANT SAFEGUARDS
4 ADJUSTMENT PROCEDURE
5 BLOCK DIAGRAM
6 SERVICE NOTES
7 CIRCUIT DIAGRAM
8 LAYOUT DIAGRAM
9 EXPLODED DRAWING
10 PARTS LIST

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1 SPECIFICATION
14” Mono Chrome Monitor
CRT SIZE : 14” 90 DEGREES
PHOSPHOR : H68AU
FACEPLATE : NON-GLARE
SCAN FREQ : HOR. 31.5 KHz, 35.5 KHz, 35.2 KHz, 38 KHz
VER. 40 – 75 Hz
RESOLUTION : 640 x 480, 800 x 600, 1024 x 768
BANDWIDTH : 26 MHz, 35 MHz, 45 MHz
VIDEO SIGNAL : ANALOG R.G.B. INPUT, 1 Vp-p MAX
SYNC INPUT TYPE : H-SYNC, V-SYNC TTL
INPUT CONNECTOR : 15 PIN D SHELL
USER CONTROL : BRI, CON, POWER SW, V- SIZE, H-PHASE
INPUT VOLTAGE : AC 100 – 240V, 50/60 Hz (AUTO)
POWER CONSUMPTION: 33W MAX
DIMENSION : 385W x 370H x 385D mm
NET WEIGHT : 7.5 Kg
SAFETY : UL, CSA, DHHS, CE (LVD)
EMI : FCC – B, CE (EMC)

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2 OPERATING INSTRUCTIONS
2-1 POWER SWITCH
Power on/off switch is a push button. To turn on the power of the unit,
press this switch. To turn off the unit, press it again.
2-2 POWER-ON INDICATOR
The power-on indicator is lit when the power is turned on.
2-3 BRIGHTNESS CONTROL
Turn the brightness control clock-wise to increase the brightness and
counter clock-wise to decrease it.
2-4 CONTRAST CONTROL
Turn the contrast control clock-wise to increase the contrast and counter
clock-wise to decrease it.
2-5 HORIZONTAL PHASE CONTROL
Turn the control clock-wise to adjust the screen to the left and counter
clock-wise to adjust the screen to the right.
2-6 VERTICAL SIZE CONTROL
To adjust vertical size for all modes: turn the control clock-wise or
counter clock-wise until a suitable height is achieved.

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3 IMPORTANT SAFEGUARDS
For your own safety read all instructions and retain them for further
reference.
3-1 POWER PLUG
This display monitor is equipped with a 3-wire grounding type power
plug. The third pin provides a safety ground for the display frame and
will only fit into the power outlet of compatible configuration.
Contact your technician to replace an obsolete outlet. Do not defeat the
safety purpose of the grounding plug.
3-2 POWER INPUT
This display should be operated only from the types of power source
indicated on the label. If there is any question about the type of power
supplied to the outlet consult your technician or dealer.
3-3 VENTILATION
Openings on the cabinet back and bottom are provided for ventilation.
To insure reliable operation and to protect the display from overheating
these openings must not be blocked or covered. Do not place the display
near or over a radiator or heating vent. If this unit is installed within
another enclosure be sure that adequate ventilation has been provided.
Never push objects of any kind through the cabinet openings as they may
come into contact with dangerous voltage points or cause short circuits
that could result in fire or electrical shock.
3-4 ATTACHMENTS
Signal sources must be of approved types and properly grounded. If
safety standards are to be maintained a service technician should perform
routine safety tests to determine that all the equipment are in safe
operating condition.
Overloaded or poorly grounded AC power systems can cause severe
difference in ground potential between the display and the signal source.
This is the case particularly on long video lines where the display and the
source are plugged into different AC power circuits. Besides causing
signal instability, ground potential may be great enough to present a
shock hazard. Ground potential tests should be part of routine safety
check carried out by a service technician.

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3-5 INSTALLATION
Do not place the display on an unstable cart, stand or shelf where it may
fall and injure personnel or cause damage to the equipment. Install the
unit on a solid firm base whenever possible.
Route the power cord and all cables so they will not be walked on or
tripped over. Do not allow anything to rest on the power cord.
Do not install this display in wet areas or wherever it may be exposed to
rain or water. Do not spill liquid of any kind on the unit.
3-6 CLEANING
Unplug the power cord from the outlet before cleaning the display. Use
only a damp cloth and mild detergent.
Do not use strong liquid cleaner or aerosol sprays. Do not attempt to
clean the interior of the unit; this action must be performed by the service
technician as required during normal maintenance.
3-7 SERVICING
Removal of the back by an unauthorised person may expose the user to
dangerous voltage or other hazards.
Refer all servicing to qualified service personnel. Unplug the display
from the power outlet and notify the service technician.
(a) If liquid has been spilt into the display.
(b) If the display has been exposed to rain or water.
(c) If the display has been dropped or the cabinet damaged.
(d) If fuse continue to blow.
(e) If the power cord is damaged or frayed.
(f) If a distinct change from normal operation is apparent.

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4 ADJUSTMENT PROCEDURE
This alignment procedure is for adjusting/testing picture performance. In
order to obtain the optimum result, the following adjustment sequence
must be followed step by step:
4-1 Check B+ voltage
(a) Test pattern: cross hatch
(b) Set up external brightness and contrast VR to central position
(c) Make sure 30Vdc = 0.1 Vdc use digital multimeter positive lead
test D913 negative point, negative lead to ground.
4-2 Vertical linearity adjustment:
(a) Test pattern: cross hatch
(b) Set up external brightness and contrast VR to central position
(c) Adjust VR300 to make equal distance between top-centre and
bottom-centre.
4-3 Horizontal-hold adjustment:
(a) Test pattern: cross hatch
(b) Set up external brightness and contrast VR to central position
(c) Turn off horizontal-sync (pin to ground)
(d) Adjust VR400 to make pattern upright.
4-4 Geometric distortion pattern adjustment:
(a) Test pattern: cross hatch
(b) Set up external brightness and control VR to central position
(c) Adjust eight magnets on the deflection yoke make picture to the
best condition.
4-5 Video Centering adjustment
(a) Test pattern: cross hatch
(b) The video is centered by rotating the two small magnetic rings at
the rear of the yoke.
4-6 Horizontal-width adjustment
(a) Test pattern: cross hatch
(b) Set up external brightness and contrast VR to central position
(c) Adjust L401 to make picture width within 228 + 4 mm.
4-7 Vertical height adjustment:
(a) Test pattern: cross hatch
(b) Set up external brightness and contrast VT to central position
(c) Adjust VR301 to make height to 170 = 4 mm.

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4-8 Vertical hold (Free-run 52Hz) adjustment:
(a) Disconnect video signal
(b) Use frequency counter O lead, measure vertical yoke point,
adjustment VR302 make frequency value to 52Hz.
4-9 Raster adjustment:
(a) Disconnect video signal
(b) Set up external brightness VR to maximum, external contrast VR
to maximum
(c) Adjust VR403 have luminance equal to over 55FL
4-10 Brightness check:
(a) Test pattern: full white
(b) Set up external brightness and contrast VR to maximum position
(c) Over 55FL
4-11 Focus adjustment:
(a) Test pattern: “H” character pattern
(b) Set up external brightness and contrast VR to central position
(c) Adjust VR402 have central picture and 4 corners to be
distinguished.

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