LITE-ON C1786PNS Service Manual

MEDION

Service Manual

17-inch Color Monitor
C1786PNST (MD 1786LH)

Service Manual Versions and Revision

No. Version Release Date Revision

1. 1.0 July 31, 2001 Original release

Copyright

Copyright 2001 LiteOn Technology Corp.

All Rights Reserved

This manual may not, in whole or in part, be
copied, photocopied, reproduced, translated, or
converted to any electronic or machine readable
form without prior written permission of LiteOn
Technology Corp.

C1786PNST (MD 1786LH) Service Manual.

Printed in Taiwan.

Trademarks

LiteOn is a registered trademark of LiteOn
Technology Corp.

All other trademarks are the property of their
respective owners.

MEDION

MD 1786LH (C1786PNST)

Table of Contents

1. Precautions.........................................................................................................2

2. Product Specifications .......................................................................................5

3 Control Location and Functions ...................................................................... 10

4. Operation Theory.............................................................................................. 11

5. Alignments and Adjustments ........................................................................... 16

6. Troubleshooting............................................................................................... 20

7. Recommended Spare Parts List ....................................................................... 27

8. Block Diagram ................................................................................................ 29

9. Exploded Diagrams .................................................................................. Inserted

10. PCB Diagrams ......................................................................................... Inserted

11. Schematic Diagrams ................................................................................ Inserted

Page 1

MEDION

MD 1786LH (C1786PNST)

1 Precautions

Follow these safety and servicing precautions to prevent damage and to protect against potential hazards
such as electrical shock and X-rays.

1-1 Safety Precautions

1-1-1 Warnings

1. For safety purpose, do not attempt to modify
the circuit board, and always disconnect the AC
power before performing servicing on the
monitor.

2. Operation of the monitor outside its cabinet or
with the cover removed involves the risk of
shock hazard. Repair work on the monitor
should only be attempted by service personnel
who are thoroughly familiar with all necessary
safety precautions and procedures for working
on high voltage equipment.

3. Do not lift the CRT by the neck. After
completely discharging the high voltage anode,
handle the CRT only when wearing shatterproof
goggles. Try to keep the CRT away from the
body during handling.

4. High voltage should always be kept at the rated
value, no higher. Only when high voltage is
excessive are X-rays capable of penetrating the
shell of the CRT. Operation at high voltages
may also cause failure of the CRT or high
voltage circuitry.

nonmetallic control knobs, insulating materials,
cabinet backs, adjustment and compartment
covers or shields, isolation resistor-capacitor
networks, mechanical insulators, etc.

3. AC Leakage Current Check

Always perform the AC Leakage Current
Check on the exposed metal parts, including
metal cabinets, screwheads and control shafts,
as follows:

a) Plug the AC line cord directly into a rated

AC outlet. Do not use an isolation
transformer during the check.

b) Use an AC voltmeter with at least 5000

ohms per volt sensitivity as follows:

Connect a 1500 ohms, 10 watt resistor
paralleled by a 0.15uF AC capacitor in series
with all exposed metal cabinet parts and a
known earth ground, such as electrical
conduct or electrical ground connected to
earth ground, as shown in the Figure 1-1.
Measure the AC voltage across the
combination of resistor and capacitor.

Figure 1-1. Set Up For AC Leakage Current Check

5. The CRT is especially constructed to limit X­ray emission to 0.5mR/HR at 300 microamperes
anode current. To ensure continued X-ray
protection, replace the CRT with only the same
or equivalent type as the original, and adjust the
anodes voltage to the designated maximum
rating, never to exceed.

1-1-2 Safety Checks

Before returning the monitor to the user, perform
the following safety checks:

1. Inspect to make certain that each lead dress is
not pinched or that hardware is not lodged
between the chassis and other metal parts in
the monitor.

2. Inspect all protective devices such as

To kn o w n

earth ground

0.15ufd

1500 ohm 10 watt

To ex posed m e tal

cabinet part

c) Reverse the AC plug at the AC outlet and

repeat the steps for AC voltage
measurements for each exposed metal part.

d) Voltage reading must not exceed 0.3 volts

RMS, equivalent to 0.2 milliampere AC. Any
value exceeding this limit ill constitute a
potential shock hazard and must be
corrected immediately.

PrecautionsPage 2

MEDION

MD 1786LH (C1786PNST)

1-1-3 Product Safety Notices

Many electrical and mechanical parts in this chassis have special safety-related characteristics which are
often not evident from visual inspection, the protection afforded by them may not be obtained by replacing
them with components rated for higher voltage, wattage, etc. Before replacing any of these components,
consult the Recommended Spare Parts List given at the end of this manual. Any of the replacements that do
not provide the same safety characteristics may result in shock, fire, X-ray emission or other hazards.

1-2 Servicing Precautions

Warning: An electrolytic capacitor installed with the wrong polarity might explode.

Caution: Before performing servicing covered by this service manual, read and follow the Safety Precautions

section of this manual.

Note: If unforeseen conflict between the following servicing precautions and any of the safety

precautions, always follow the safety precautions

1. Follow closely the servicing precautions printed on the monitor cabinet and chassis.

2. Always unplug the AC power cord from the AC power source before removing or installing any component

or assembly, disconnecting PCB plugs or connectors and connecting a test component in parallel with a
capacitor.

3. When replacing parts or circuit boards, clamp the lead wires around the component before soldering.

4. When replacing a high wattage resistor (>0.5W metal oxide film resistor) in the circuit board, keep the

resistor about 1 cm (1/2 inch) away from the circuit board.

5. Keep wires away from the high voltage or high temperature components.

6. Keep wires in their original positions so as to minimize interference.

7. Always connect a test instruments ground lead to the instrument chassis ground before connecting the

positive lead; always remove the instruments ground lead last.

After putting the rear cover back and make sure the monitor is working properly, the Hi-Pot &
Ground Continuity tests MUST BE performed before the monitor is returned to user.

1-3 Hi-Pot Test

1. Test Equipment

Puncture test model PM5530 ADT or KIKUSU TOS-8750 voltage tester or equivalent approved equipment.

Note : The test equipment must be calibrated in regular period.

2. Test Setup

a) Apply voltage : DC 2100 VDC

b) Test duration : 3 seconds

c) Cutoff current should be set to 3 mA

3. Test Procedure

a) Unplug power cord from AC source.

b) Put the power switch of the monitor in the ON position.

c) Leave signal cable un-connected.

Precautions

Page 3

MEDION

d) Plug monitor power cord to the Hi Pot tester terminals.

e) Turn on tester and watch the indicator or beeper.

f) If the indicator lamp lighten, or beeper beeps, the test fails.

1-4 Ground Continuity Test

1. Test Equipment

AC low ohm tester TOS-6100 or equivalent approved equipment.

Note : The test equipment must be calibrated in regular period.

2. Test Setup

a) Test duration : 3 seconds

b) Set current limit at 25 A

c) The grounding resistance must be less than 0.1 ohm.

3. Test Procedure

a) Plug the monitor power cord to the tester terminals.

MD 1786LH (C1786PNST)

b) Make sure all connections are well-contacted.

c) Turn on monitor power and tester power.

d) Press Test button.

e) If green light shows up, means test OK.

If red light shows up, means test fails.

f) If the Tester has a digital display, the resistance value must not exceed 0.1 ohm.

Note : Be sure not to touch the metal portion of the signal cable head during testing.

PrecautionsPage 4

MEDION

2 Product Specifications

2-1 Specifications

17-inch (15.8-inch Visual image area), sloted mask, 90 degrees

Picture Tube

deflection, dot type black matrix, medium short persistence
phosphor, dark tint, non-glare/ anti-static screen,

0.27 mm dot pitch

MD 1786LH (C1786PNST)

Sc anning Frequency

Maximum Resolution 1280 dots (H) x 1024 lines (V) @75Hz refresh rate

Display Area 310 mm (H) x 230 mm (V) typical

Display Characters 80 char. x 60 rows on a 10 x 10 matrix

Disp la y C olors Analog
Input

Sync hronizatin Signals Se parate Sync: horizontal/vertical, TTL, positive or negative

Sync hronization
Frequencies

Signal Connectors 15-pin, D-shell connector

Video Signals Analog : 0.7 Vp-p, RGB positive

Power Input 75 Watts (maximum) AC rated voltage, 100VAC to 240VAC

Misconvergence Center Area : <

User Contro ls Po wer On/O ff, C o ntrast, Brightness, Horizontal Size, Horizontal

VGA, Super VGA, 1024x768@60/75/85/100 Hz

1280x1024@60/75 Hz

Unlimited Colors

Horizontal : 30 to 86 kHz
Vertical : 50 to 120 Hz

0.25 mm; Corner Area : < 0.3mm

Position, Vertical Size, Vertical Position, Pincushion, Trapezoid,
Rotation, C olor tempera ture, Language, Display Frequency,
Degauss, Recall, H. Moire,V. Moire, Pincushion Balance,
Parallel, OSD Position, Top Corner, Bottom Corner

Service Controls PWB-1613

PWB-1611 : power voltage adjust (VR801), high voltage adjust

Preset Modes 14 (see Table 2-2. Timing Chart)

o

Environmental
Considerations

Operation temperature : 10
Operation Humidity : 20% to 80% ambient
Storage temperature : -40
Storage Humidity : 10% to 90% (non-condensing)
Altitude : Non operating 40,000 feet sea level
operating 10,000 feet sea level

C to 40oC ambient

o

C to 65oC ambient

Note: Above specifications are subject to change without prior notice.

Product Specifications

Page 5

MEDION

2-2 Signal Cable Pin Connections

Table 2-2. Signal Cable Pin Assignment

Pin Signal Pin Signal

1 Red video 9** +5V

2 Green video 10 Digital Ground

3 Blue video 11 Ground

4 Ground 12 S DA

5* NC 13 H-Sync

6 Red gro und 14 V- Sync/VCL

7 Green gro und 15 S C L

MD 1786LH (C1786PNST)

8Blue ground

Note * This pin is used for selftest detection. Connect this pin to ground at the PC end.

** For PC 99: This pin will provide +5V from PC side.

Product SpecificationsPage 6

MEDION

MD 1786LH (C1786PNST)

2-3 Timing Chart

This section describes the timings that the computer industry recognizes as standard for computer-generated
video signals.

Table 2-3. Timing Chart

MODE 1234567891011121314

H. Dots 720 640 800 640 800 1024 800 1024 800 1280 1024 1024 1280 1280

V. Lines 400 480 600 480 600 768 600 768 600 1024 768 768 1024 960

H. Freq. (KHZ) 31.47 31.47 37.88 43.27 46.8 48.36 53.67 60.02 62.966 64.34 68.68 80 80 85.938

V. Freq. (HZ) 70.08 59.95 60.32 85 75 60 85 75.03 99.472 60 85 100 75 85

A Period (us) 31.78 31.78 26.4 23.11 21.333 20.68 18.63 16.66 15.876 15.55 14.56 12.376 12.504 11.636

B Blking (us) 6.356 6.356 6.4 5.33 5.172 4.923 4.409 3.657 4.028 3.589 3.725 3.624 3.022 3.017

C Sync. (us) 3.81 3.81 3.2 1.556 1.616 2.092 1.138 1.219 1.185 0.972 1.016 1.231 1.067 1.077

D B.P. (us) 1.907 1.907 2.2 2.22 3.232 2.462 2.702 2.235 2.37 2.248 2.201 2.12 1.837 1.508

E Active (us) 25.42 25.42 20 17.78 16.162 15.75 14.22 13 11.848 11.96 10.836 8.752 9.481 8.62

F F.P. (us) 0.636 0.636 1 1.556 0.323 0.369 0.569 0.203 0.473 0.374 0.508 0.273 0.119 0.431

G Peroid (ms) 14.27 16.68 16.58 11.76 13.333 16.67 11.76 13.33 10.05 16.67 11.77 9.988 13.329 11.764

H Blking (ms) 1.557 1.43 0.739 0.67 0.533 0.786 0.578 0.533 0.544 0.642 0.582 0.483 0.525 0.593

I Sync. (ms) 0.064 0.064 0.106 0.069 0.064 0.124 0.056 0.05 0.048 0.047 0.044 0.074 0.038 0.035

J B.P. (ms) 1.08 1.02 0.607 0.578 0.448 0.6 0.503 0.466 0.48 0.501 0.524 0.397 0.475 0.547

K Active (ms) 12.71 15.25 15.84 11.09 12.8 15.88 11.18 12.8 9.526 16.03 11.18 9.505 12.804 11.171

L F.P. (ms) 0.413 0.35 0.026 0.023 0.021 0.062 0.019 0.017 0.016 0.094 0.015 0.013 0.013 0.012

CLOCK(MHZ) 28.3 25.1 40 36 49.5 65 56.25 78.75 67.5 107 94.5 117 135 148.5

Sync H

Polarity V

- - + - ++++++++++

+ - + - ++++++++++

Horizontal

C

E

Vid eo

D

Sync

A

H.Parameters:

A: Period B: Blanking Time

C: Sync Width D: Back Porch

E: Active Time F: Front Porch

Product Specifications

Seperate Sync

Ve r t i c a l

B

F

I

K

Vid eo

J

Sync

G

H

L

V.Parameters:

G: Period H: Blanking Time

I: Sync Width J: Back Porch

K: Active Time L: Front Porch

Page 7

MEDION

MD 1786LH (C1786PNST)

2-4 Display Power Management Signal (DPMS)

Note: These power-saving states exceed the Environmental Protection Agency (EPA) Energy Star

requirements.

Table 2-4. Display Power Management Signal (DPMS)

State LED Color H-Sync V-Sync Power

Cons umption

ON Green Pulse Pulse Normal

*

OFF Amber No Pulse No Pulse <5 watts

* For power consumption : 75W Max. (@ 230V AC, preset size and maximum light output condition)

2-5 TCO Version

The monitor meets the TCO 95/99, NUTEK energy saving, electric and magnetic field requirements.
Also it is compliant with TCO 95/TCO 99 labelling scheme.

The emission from magnetic and electric field must comply with the limits specified by the Swedish Board
for Measurement and Testing, commonly known as MPR 1990 recommendations. These limits are sum­marized in the Table 2-4.

Table 2-5. TCO 95 Emission Requirements

OCT/FLVOCT/FLE

dleiFcitengaMTn52Tn002

dleiFcirtcelEm/V1m/V01

egnaRycneuqerFzHk004~2zH0002~5

eulaVSMRSMR

ecnatsiDmc03mc03

citatsortcelE

laitnetoP

V005-/+V005-/+

The monitor is designed with selected CRT and carefully routed wires around CRT, make sure exactly the
same routing scheme is used when doing CRT replacement.

Product SpecificationsPage 8