LITE-ON A1770 Service Manual

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Service Manual

17-inch Color Monitor A1770NSL/NST

Page 2

Service Manual Versions and Revision

No. Version Rele ase Date Revision

1. 1.0 July 17, 1998 Original release

copied, photocopied, reproduced, translated, or converted to any electronic or machine readable form without prior written permission of LiteOn T echnology Corp.

A1770NSL/NST Service Manual.

Printed in Taiwan.

T rademarks

LiteOn is a registered trademark of LiteOn Technology Corp.

All other trademarks are the property of their respective owners.

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A1770NSL/NST

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............................................................................................... 21

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

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

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

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

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

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A1770NSL/NST

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 own

earth

round

0.15ufd

1500 ohm 10 w att

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

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A1770NSL/NST

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

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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.

A1770NSL/NST

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

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2 Product Specifications

2-1 Specifications

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

Picture Tube

degrees deflection, dot type black matrix, medium short

persistence phosphor, dark tint, non-glare/ anti-static screen,

0.27 mm dot pi tch

A1770NSL/NST

Sc anning F req uency

Maximum Resolution 1280 dots (H) x 1024 li nes (V) @60Hz refresh rate Display Area 300 mm (H) x 225 mm (V) typical Display Characters 80 char. x 60 rows on a 10 x 10 matrix Display Colors Analog

Input Sync hroni zati n Signa ls Se par ate Sync: hori zonta l/verti ca l, T TL, posi tiv e or negati ve Sync hroni zati on

Fr eque ncies Si gnal Conne ctor s 15 -pi n, D- shel l connector Video Si gnals Anal og : 0.7 Vp-p, RGB positi ve Power Input 95 Watts (maximum) AC rated voltage, 100VAC to 240VAC Misconvergence Center Area : <

Us er Control s

VGA, Super VGA, 1024x768@60/70/75/85 Hz,

1280x1024@60 Hz

Unlimited Colors

Horizontal : 30 to 69 kHz Vertical : 55 to 120 Hz

0.3 mm; Corner Area : < 0.4mm

Power On/Off, Cont ras t, Br ightne ss, Horizonta l Si ze, Horizontal Position, Vertical Size, Vertical Position, Pincushion, Trapezoid, Rotation, Color temperature, Langua ge, Di spl ay Freque ncy, Dega uss, Recall, H. Moire, V. M o i r e

Service Controls PWB-1410 : R-bias (VR910), G-bias (VR940),

B-bias (VR970), PWB-1440 : power voltage adjust (VR801),

high voltage adjust (VR802), focus1, focus2 Preset Modes 13 (see Table 2-2. Timing Chart) Envir onmental

Considerations

Operation temperature : 5 Operation Humidity : 20% to 80% ambient Storage temperature : -40 Storage Humidity : 5% to 95% (non-condensing)

Altitude : up to3000m above sea level

C to 4 0oC ambient

C to 6 5oC ambient

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

Product Specifications

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2-2 Signal Cable Pin Connections

Table 2-1. Signal Cable Pin Assignments

Pin S ignal Pin Signal

A1770NSL/NST

1 Red video 9

2 Green video 10 Digital Ground 3 Blue video 11 Ground 4 G r o und 12 SDA 5

13 H - Sync 6 Re d gr ound 14 V- Sync/ VCL 7 Gre en gr ound 15 SCL 8 Bl ue g ro und

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

Product SpecificationsPage 6

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A1770NSL/NST

2-3 Timing Chart

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

T able 2-2. Timing Chart

Mode 1 2 3 4 5 6 7 8 9 10 11 12 13

H. D ots 720 640 640 800 640 640 800 1024 800 1024 1024 1280 1024

V. D o t s

H-freq (kHz) 3 1. 47 31.47 3 5 37.88 37.5 43. 3 46.8 4 8. 36 53.67 56.48 60.02 64.34 68.68

Sync Polarity ---+ - - + ++++++

A pe riod us 31.78 31.78 28.57 2 6.4 26. 666 23.111 21.33 3 2 0.68 18.63 17. 71 1 6.66 15.55 14.56

B Blking us 6.356 6.356 7.407 6.4 6.35 5.33 5.172 4.923 4.409 4.053 3.657 3.589 3.725

C S ync us 3.81 3.81 2.116 3.2 2.07 1.556 1.616 2.092 1.138 1.813 1.219 0.972 1.016

D B.P. us 1.907 1.907 3.175 2.2 3.81 2.222 3.232 2.462 2.702 1.92 2.235 2.248 2.201

E Acti ve us

F F. P. us 0.636 0.636 2.116 1 0.51 1.556 0.323 0.369 0.569 0.32 0.203 0.374 0.508

V-freq (Hz) 70.08 59.95 66.667 60.32 75 85 75 60 85 70.07 75.03 60 85

Sync Polarity +--+- - + + +++++

O Period ms 14.27 16.68 1 5 16.58 13.33 11.764 13. 333 16.67 11.76 1 4.27 13.33 16.67 11.77

P B lking ms 1.557 1.43 1.286 0.739 0.533 0.67 0.533 0.786 0.578 0.673 0.533 0.642 0.582

Q Sy nc ms 0.064 0.064 0.086 0.106 0.08 0.069 0.064 0.124 0.056 0.106 0.05 0.047 0.044

400 480 480 600 480 480 600 768 600 768 768 1024 768

25.42 25.42 21. 164 20 20.32

17.778

16.162 15.75 14.22 13.65 13 11.96

10.836

R B.P. us 1.08 1.02 1.14 0.607 0.407 0.578 0.448 0.6 0.503 0.513 0.466 0.501 0.524

S Active us 12.71 1 5.25 13. 714 15. 84 12.8 11.09 3 1 2.8 15.88 11.18 1 3.6 12.8 1 6.03 11. 18

T F.P. us 0.413 0.35 0.086 0.026 0.026 0.023 0.021 0.062 0.019 0.053 0.017 0.094 0.015

Seperate Sync

H orizontal

Video

Sync

H.Parameters:

A: Period B : Blanking Time C: Sync Width D: Back Porch E: Active T ime F : Front Porch

Product Specifications

Vertical

V.Parameters:

G: Period H :Blanking Time I: Sync Width J: Back Porch K: Active T ime L : Front Porch

Video

Sync

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A1770NSL/NST

2-4 Display Power Management Signal (DPMS)

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

requirements and the Video Electronics Standard Association (VESA) for Display Power Management Signal (DPMS) .

T able 2-3. Display Power Management Signal (DPMS)

State LED Color H-Sync V-Sync Power

Co nsumpti o n

ON Green Pulse Pulse Normal

STANDBY Yellow No Pulse Pulse <15 watts

SUS PEN D Ye llow Puls e N o P ulse < 15 wa tts

O FF Amb er N o Puls e No Puls e <8 wa tt s

2-6 TCO Version (Optional)

The monitor meets the TCO 92, NUTEK energy saving, electric and magnetic field requirements. Also it is compliant with TCO 95 (optional) labelling scheme.

2-6-1 TCO 92 Version

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

T able 2-4. TCO 92 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 for CRT replacement.

Product SpecificationsPage 8

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A1770NSL/NST

2-6-2 TCO 95 Version (Optional)

The TCO 95 scheme is for international and environmental labelling of personal computers. The labelling scheme was developed as a joint effort by the TCO (The Swedish Confederation of Professional Employ ees), Naturskyddsforeningen (The Swedish Society for Nature Conservation) and NUTEK (The National Board for Industry and T echnical Development in Sweden).

1) Scope TCO 95 touches on ergonomic qualities, emissions (electrical and magnetic fields), energy efficiency and

ecology (with demands for environmental adaptation for both the product and the production processes at the manufacturing plant).

2) Environmental Requirements The monitor abides by the environmental demands concerning restrictions on the presence and use of

heavy metals, brominated and chlorinated flame retardants, CFCs (freons), and chlorinated solvents, among other things. The monitor is also recyclable.

3) Energy Requirements The monitor also follows the energy requirements that, after a certain period of inactivity, the monitor

shall reduce its power consumption to a lower level in one or more stages.

4) Others The monitor meets the strict environmental demands for the reduction of electric and magnetic fields,

physical and visual ergonomics and good usability.

Table 2-5. TCO 95 Visual Ergonomics

erutaeFdradnatSnoitpircseD

ytiraeniLsselro%1 ehtotderapmocsworrosnmulocfohtgnelniecnereffiD

ecnanimuLyalpsiD)tsaelta(2m/dc001

ecnanimuL ytimrofinU

sselro1:7.1 ehtnihtiwecnanimulnimotxamehtneewtebsioitarehT

.aeraevitcaelohw

.rotinomehtforetnecehthguorhtshtgnelgnidnopserroc

Product Specifications

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3 Control Location and Functions

(1) (2) (3) (6)(5)(4)

3-1 Front Panel

A1770NSL/NST

(1) Function Key (2) Decrease Key (3) Increase Key (4) Select Key (5) Power LED (6) Power ON/OFF

3-2 Front Panel Keys Functions

1. Function Key: Display the main menu, and exit the adjustment screen and save adjustments.

2. Decrease Key: Scroll across main menu, highlighting control to be adjusted. Decrease value of selected control. Toggle between Contrast and Brightness adjustment screens.

3. Increase Key: Scroll across main menu, highlighting control to be adjusted. Increase value of selected control. Toggle between Contrast and Brightness adjustment screens.

4. Select Key: Press once to display adjustment screen. Press again, for some controls, to toggle between controls shown in pairs on main menu.

5. Power LED: Display different modes (ON, standby, suspend or OFF) of the monitor by showing different color for each mode.

6. Power ON/OFF: To turn the monitor ON and OFF.

3-3 Adjustment Procedure

1. Press (6) key to turn on the monitor.

2. At normal condition, press (1)on the front panel to activate the on-screen manager (OSM) menu. But to enter the internal adjustment menu, keep pressing (1) & (4) key simultaneously and then press (6) key.

3. To select a user control, press (2) or (3) key repeatedly until the control is highlighted.

4. To adjust the value for particular control, press (4), then press the (2) or (3) key to obtain the desired value. There are a few parameters that do not require any adjustment, like Manual Degauss, Memory Recall.

5. Some controls are grouped in pairs on the main menu. Press (4) key to toggle between them.

6. To save your adjustments and exit screen, press (1) key. The menu will automatically clear out from the screen if no keys are pressed within 30 seconds.

Page 10 Operation Theory

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A1770NSL/NST

4 Operation Theory

This is a fully digital controlled multi-sync color monitor that is compliant with DDC1 and 2B Plug and Play VESA standard and offers the following main features.

4-1 Main Features

1. Simplified design with minimum components.

2. The NOVATEK NT68P61A processor-- that has I

brightness-- offers the functions for: (a) Contrast, (b) Brightness, (c) H-size, (d) H-position, (e) V-size, (f) V-position, (g) Pincushion, and (h) Trapezoid.

C BUS controlled geometric correction, contrast and

In addition, it also offers more functions as: (a) Sync. processor, I/P and O/P, (b) Mute, (c) Power saving

- Suspend & Stand-By, (d) Power saving override, (e) DDC1/2B, (f) I

C Bus for auto-alignment through

signal cable (g) CS1/CS2/CS3/CS4 for linearity and size compensation.

3. Stores up to 14 factory preset modes and offers 8 user modes. There are 16 function icons at OSD. They

are controlled by

2 keys on front panel.

4. Powerful PHILIPS TDA4854 and TDA4866 present the following useful functions: (a) Pincushion, (b)

Trapezoid, (c) V-Position, (d) V-Size, (e) Vertical’ s “C” and “S” correction -- factory adjust, (f) Pincushion’ s V. position correction, (g) Corner correction -- factory adjust, (h) Pincushion unbalance correction -factory adjust, (i) Parallelogram distortion -- factory adjust, (j) Moire cancellation -- factory adjust, (k) Xray protection, and (l) Full horizontal and vertical auto sync capability.

5. Software controlled auto shut off function activated if fH < = 29 kHz and fH > = 70 kHz.

6. Full range AC input and simplified line filter design.

4-2 Microcontrol Section

1. This monitor uses NOVATEK NT68P61 CPU. It contains a 6502 8-bit CPU core, 256 bytes of RAM

used as working RAM and stack area, 24k bytes of OTP ROM, 14-channel 8 bit PWM D/A converter, 2-channel A/D converters for key detection saving I/O pins, internal H. sync and V. sync signals processor providing mode detection, and an I2C bus interface. When H/V sync through D-Sub signal cable enter pin 39 and pin 40, the CPU performs frequency / polarity detection and calculate and send to H/V sync OUT. Then CPU reads the data from I703 and transfer to device 4854 and some DAC in CPU, above operation takes about 500 ms.

2. There allowed 14 factory preset modes and 8 user modes. There are 8 functions, Contrast, Brightness, H.

Size, H. Position, V. Size, V. Position, Pincushion, and Trapezoid, all controlled by OSD icon which can be adjusted by user.

3. The pin 24 and pin 25 are used for A TE function. When CPU receives C6 as slave address, it will operate

in ATE mode which is used for auto-alignment. After alignment the data will be stored in I703.

4. The user control parameters are selected by OSD icons, through

2 keys, they are detected by

sensing the voltage through R710, R740, R711, R743, R741, R711 to pin 13 and 14 of I701.

4-3 Deflection Section

1. I2C -- autosync deflection controller is TDA4854.

2. The TDA4854 is a high performance and efficient solution for autosync monitors. All functions are

controllable by I control all functions.

Operation Theory Page 11

C bus. SDA and SCL signals come from microprocessor feed to pin 19 and pin 18 to

Page 14

A1770NSL/NST

4-3-1Horizontal Section

1. The oscillator is driven by the currents in R419 and R420. The minimum oscillator frequency is determined by R419 and the maximum frequency is determined by R420.

2. Horizontal sync comes into pin 15 through R318. And horizontal flyback pulse comes into pin 1 through R401 and by pass filter C403 from pin 9 of FBT and C453, R4C2, Q414, R4C3 for AFC loop.

3. Horizontal driver (pin8) O/P to Q401 via C410.

4-3-2 Vertical Section

1. V ertical sync comes into pin 14 through R317.

2. The free running frequency is determined by R301 and C301.

4-3-3 Vertical O/P section

1. The differential output currents from pin 13 of Vout1 and pin 12 of Vout2 can be directly coupled to the vertical deflection booster pin 1 and pin 2 of TDA4866.

2. The TDA4866 has two output stages which are current driven in opposite phase and operate in combination with the deflection coil in a full bridge configuration.

3. This IC is powered by two sets of positive voltage. (+12V at pin 3, +50V at pin 7).

4-3-4 E-W/T rapezoid and H. Width Contr ols

1. The horizontal O/P stage uses diode modulator D419, D423, C411, C412, L409 and C418 for East-West (Pincushion) Trapezoid and H. width controls.

2. The scan current is determined by B is accomplished by Darlington pair Q418 and Q419 by coupling a parabola waveform from pin 11 of TDA4854. The H. width / corner and trapezoid correction are also accomplished by this pin 11. The DC level controls H. size. The AC level is combined with side pin and trapezoid corners functions.

minus Vm ( the voltage of C418) values and the pincushion control

4-3-5 X-Ray Protection

1. To avoid X-ray hazard, a DC voltage generated by pin 6 of FBT and rectified by D408, C432 and divided by R403, R404 and R405 come into pin 2 of TDA4854.

2. If this voltage is higher than 6.39 V, then TDA4854 will be activated to float HUNLOCK (pin17), H. DRV( pin 8), B DRV (pin 6), VOUT1 (pin 12), VOUT2 (pin13). After that all deflection circuit stop working.

4-3-6 G1, Blanking and Brightness

1. The vertical blanking signal comes from two ways. One is from pin 8 of I301 (TDA4866), the other is from vertical sync (pin 32 of I701). These two positive vertical pulses through Q406 amplified and converted into negative pulse and sent to G1 for vertical blanking.

2. In protection mode or an out-of- range situation HUNLock will send 5 V pulse to saturate Q406 and to cutoff Q407, then G1 will go down to -140V. During the mode change, Mute acts as same as HUNLock’s.

3. The brightness is controlled by CPU pin 1 through PNP transistor Q407. The lower control voltage causes Q407 conducts harder to get brighter raster and a higher control voltage causes Q407 conducts lighter to get lower brightness.

Page 12 Operation Theory

Page 15

A1770NSL/NST

4-3-7 Contrast Section

1. Contrast is controlled by I701 through I2C bus to I501 (TDA4886) directly.

2. Beam current is detected through T402 (FBT) pin 7, C429, VR401, R460, and detected voltage feeding

into R461, R4F1, Q410, R430, R469, R524 to control I501 pin 24 voltage. When I501 pin 24 voltage drops below 5V, the ABL function will happen.

4-3-8 H/V size breathing compensation

1. Beam current is sensed as above section (4-3-7 item 2) and this voltage routes through R458, C460,

Q409, R436, R459, then through R418 to I401 pin 31 for H. size compensation, through R302 to I401 pin 21 for V size compensation.

4-3-9 Dynamic focus circuity

The dynamic focus is applied to improve the corner focus performance, it includes horizontal and vertical dynamic focus.

1. Horizontal and vertical dynamic comes from I401 pin 32 and amplified through C450, R499, Q431, Q404,

Q403, R437 and feed to FBT dynamic focus pins.

2. This amplifier need 800V voltage supply, it comes from FBT pin 2 and rectified through R4C6, D422 and

C448.

4-4 Power Supply Section

4-4-1 AC Rectifier

The circuit can accept 90 V to 264 V AC input through D801~D804 bridge diodes and C808 filtering to get DC 126 V~364 V for power conversion in T802.

4-4-2 Line Filter

It consists of C801, C802, C803, C816, C852, C853, C807 and T801 and meets EMI regulation.

4-4-3 Power LED Status

1. The LED has 3 leads with common cathode to emit green and amber color light for different power

saving indications. It is controlled by CPU.

2. Normal : Green light

Amber LED is off because CPU pin 35 is high and pin 34 is low, only green LED is turned on.

3. Standby / Suspend : Y ellow light

CPU pin 34 and pin 35 are low, then green and amber LED are turned on. That is yellow.

4. Off Mode : Amber light

CPU pin 34 is high and pin 35 is low, then green is off and amber is illuminated.

Operation Theory Page 13

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A1770NSL/NST

4-4-4Auto Degaussing

When S701 turns on, pin 19 of I701 will send a signal to Q802 and turns on RL801 for degaussing. After 4 seconds, it will turn off RL801 automatically.

4-4-5 PWM Control

1. Start Up The I801 (MC3842) gets power from R807, R873, C812 and pin 7 voltage reaches 16 V for starting up.

The I801 starts oscillation at 22 kHz, sawtooth on pin 4 and pin 6 output to drive Q803/T802. Once Q803 switching on, D806, C804 set up an 15 V to keep I801 working through D808 auxiliary voltage.

2. Regulation The DC O/P voltage is proportional to the auxiliary voltage, so I801 pin 2 senses the feedback voltage

from the divider R802, R823, VR801 and R821 to compare with the built-in 2.5 volts reference voltage for error amplifier operation. Finally pin 6 can modulate the different duty cycle by VR801 setting to achieve regulation purpose.

4-4-6 Synchronization

1. Normal Mode The sync pulse from FBT (31 kHz~69 kHz) via C815, R826, D824, C814 and R816 to pin 4 of I801 to

keep I801 synchronized with horizontal sync input frequency.

2. Power Saving Modes: Standby/Suspend Because there is no pulse from FBT, so the free-run frequency is decided by R815 and C814 and the

SMPS works at 22 kHz.

3. Override The horizontal free run frequency is about 62.5 kHz under override condition, SMPS is synchronized to

this frequency.

4-4-7 O.V.P.

If the auxiliary voltage is higher than zener voltage ZD807 (18 volts) and makes pin 3 of I801 higher than 1 V, pin 6 duty cycle is limited to have the OVP activated.

4-4-8 O.P.P.

The excess current of T802 through R813, R865 and R864 can develop enough voltage on pin 3 then limit the power delivered because the pin 6 duty cycle is limited too.

4-4-9 Step Up Power Supply For FBT

1. The B+ of FBT is proportional to horizontal frequency, that is the higher frequency, the higher voltage. The basic voltage is 55 volts from T802 pin 3 via D840, L812 and the gate control of Q807 comes from I401 pin 6 via Q808, Q809 and D821. The duty cycle is controlled by C843, C462, R489, R846 and R856, R857, R858 VR802 combination ratio.

2. The regulation and boost up (from 68 V to 155 V or more, on demand). The H.V. is set at 25 kV (zero beam) by VR802 which senses the secondary O/P from FBT. The booster comprises Q807, L801, D820, C425 and I802 to offer the required B+ for different frequency modes.

Page 14 Operation Theory

Page 17

A1770NSL/NST

4-5 V ideo Amplifier Section

1. RGB signal inputs are terminated by R501, R531 and R561 then pass through the coupling capacitors

C503, C533 and C563 to the IC501 TDA 4886 preamplifier.

2. The amplifier RGB signals (0~3 Vpp) are adjusted by I

comes from pin 16 of TDA4854 to set up the equal clamp level.

3. The video output stages are amplified by I901 (LM2407).

4. The RGB cathodes cut off are adjusted by VR910, VR940 and VR970.

5. Under override condition, “NO SIGNAL” will show on the screen.

C bus from I501, pin 5 is for clamp pulse which

4-6 OSD (On Screen Display) Circuit

1. The I502 HTV018-08 is OSD IC. The OSD signals are worked by positive vertical pulse from I701 pin 32

that goes through R517 to I502 pin 10, and positive horizontal pulse from T402 pin 9 goes through C453, R422, Q414, R4C3 to I502 pin 5. CPU I701 pin 26, 27 (I2C bus) transfers information to I502 pin 7, 8.

2. The OSD R. G. B signals and blanking signal are terminated at I502 pin 15,d 14, 13, and 12 to I501 pin 2,

3,4, and 1, then the OSD picture appears.

Operation Theory Page 15

Page 18

A1770NSL/NST

5 Alignments and Adjustments

This section of the service manual explains how to make permanent adjustments to the monitor settings.

5-1 General Adjustments

5-1-1Adjustment Conditions

a) Power Supply

Apply AC 115 V or 220 V

b) Warm-up Time

The monitor must be powered on for 15 minutes before starting any alignment, but requires 30 minutes of warm-up time for convergence adjustment.

c) Signal Input

1. Video: RGB Analog, 0.7 Vp-p, positive

2. Synchronization: Horizontal and vertical TTL signal, separate, positive or negative

3. All adjustments should be made using a signal of FH = 31.468 kHz, FV = 60 Hz, unless otherwise

defined.

5-1-2 Equipment Required

The following equipments are necessary for adjustment procedures:

1. Volt-ohm-A meter (Sanwa FD-750C or equivalent)

2. 30 kV high voltage probe (HP34111A)

3. Oscilloscope (TEK2235 or equivalent)

4. Minolta Color Analyzer II

5. Signal generator (IBM PC with proper display cards or Chroma 2000)

6. Screwdriver

5-1-3 Switching Power Supply and Regulator Adjustment

a. The regulated B+ control has been preset in the factory and needs no adjustment. However, if any repair

is made on the power supply section, the following readjustment procedures are recommended:

1. Allow the monitor to warm-up for about 15 minutes.

2. Apply XGA (1024 x 768 @ 68 kHz/85 Hz) signal to the monitor.

3. Connect a DC voltage meter to D814 “-” (on the control PCB), and adjust VR801 for 12.8 +

0.2 V DC

4. If a fuse is broken during adjustment, remember to replace it with the exact same type of fuse.

b. If necessary, follow the following procedures to enter the factory mode.

1. Short ATE pin to GND wire and put COM wire short COM and A TE 1 at power off condition.

2. Press both

Now, we are in the factory preset mode.

3. When turns the power off, this monitor will go back to normal mode (user mode).

4. When finish the normal alignment. Open ATE pin and change GND wire to GND 1, put COM wire to

short COM and DDC.

key and 2 key simultaneously then power on.

Page 16 Alignments and Adjustments

Page 19

A1770NSL/NST

5-2 Alignment Procedures

5-2-1 High Voltage Adjustment

CONDITION

Display image : Crosshatch pattern

PROCEDURE

Connect DC meter to TP3 and adjust VR802 to obtain a DC voltage of 152 ± 1V DC for CPT CRT M41AGE 93x46C or M41AGE83x46C.

5-2-2 Screen and White Balance Adjustment

CONDITION

Press

and 2 buttons simultaneously when switching the power On.

Bias VRs : VR910, VR940, VR970 Display image : No video

PROCEDURE

1 Raster color setting 1-a. Set brightness (OSD Icon) to -30 V at G1 and 600 V at G2. 1-b Adjust VR910, VR940 and VR970 to maximum. 1-c Adjust VR940 to y=0.9 ± 0.2 FL. 1-d Adjust VR910 to get x=280 ± 5 and VR970 to get y=280 ± 5 1-e Adjust brightness to raster just distinguish.

CONDITION

Display image : 50 mm x 50 mm white block pattern

PROCEDURE

2 6500

K color temperature setting 2-a. Set brightness to cutoff and contrast to maximum. 2-b Move cursor on OSD to choose color temperature icon. 2-c. Press

key to G gain then adjust G gain = 68 value, then adjust B, R to y=329±5, x=313±5.

2-d Adjust contrast to set y=40±2FL 2-e Check x=313±5, y=329±5.

3 9300

K color temperature setting 3-a. Set brightness to cutoff and contrast to maximum. 3-b Move cursor on OSD to choose color temperature icon. 3-c. Press

key to G gain then adjust G gain = 71 value, then adjust B, R to y=311±5, x=281±5.

3-d Adjust contrast to set y=40±2FL 3-e Check x=281±5, y=311±5. 4 Full white ABL setting

CONDITION

Display image : full white pattern 4-a Set brightness to cutoff and contrast to maximum.

Alignments and Adjustments

Page 17

Page 20

A1770NSL/NST

4-b. Adjust VR 401 to y=28FL ±2FL. 4-c. Check the white balance at 5FL and 28FL. 4-d. Repeat all the procedures in 5-2-2 section until the best white balance is obtained, then power off.

5-2-3Focus Adjustment

CONDITION

Display image : “e” character pattern

PROCEDURE

1. Set brightness to cutoff and contrast to maximum.

2. Adjust top VR at T402 (static focus VR) to make vertical line clear.

3. Adjust center VR at T402 (dynamic focus VR) to make horizontal line clear.

4. Repeat above procedures to get best focus.

5-2-4Dynamic focus Adjustments

1. Horizontal dynamic focus set Hf=340V in phase (compare with video signal).

2. V ertical dynamic focus set Vf=160V in phase.

5-2-5Static Convergence Adjustments

Static convergence involves alignment of the red, blue and green lines in the center area of the display. Note : The monitor requires 30 minutes of warm-up time for convergence adjustment.

CONDITION

Display image : Crosshatch pattern Warm-up Time : 30 minutes

PROCEDURE

1. Set brightness and contrast to display a well-defined pattern.

2. Ensure the convergence magnet rings are correctly positioned on the CRT.

Page 18 Alignments and Adjustments

Page 21

Figure 4-1. Convergence Magnets on the CRT

A1770NSL/NST

CRT

FRONT

8 7 6 5 4 3 2

1) Setup Bolt 2) Bow Magnet 3) Band 4) 2-Pole Magnet

5) Spacer 7) Spacer

9) Holder

6) 4-Pole Magnet

8) 6-Pole Magnet

11) Tabs10) Band

3. Rotate the individual rings of 4-pole convergence magnets by changing the spacing between the 2 tabs to

converge the vertical red and blue lines at the center of the screen.

4. Rotate the pair of rings of 4-pole convergence magnets by maintaining spacing between the 2 tabs to

converge the horizontal red and blue lines at the center of the screen.

5. Rotate the individual rings of 6-pole convergence magnets by changing the spacing between the 2 tabs to

converge the vertical red, blue and green lines.

6. Rotate the pair of rings of 6-pole convergence magnets by maintaining spacing between the 2 tabs to

converge the horizontal red, blue and green lines.

7. Repeat the steps from 3~6 until the best convergence is obtained.

Figure 4-2. 4-pole and 6-pole Magnets Movement

Red/ Blue Gree n

6-pole magn ets movement

Blue Red

Red/ Blue

Green

4-pole magn ets movement

Note : The 4-pole magnets and the 6-pole magnets interact, making dot movement complex.

Alignments and Adjustments

Page 19

Page 22

A1770NSL/NST

5-2-6 Degaussing

Degaussing is required when poor color impurity appears on the screen. This monitor uses an automatic degaussing circuit that is activated when the power is on. The automatic degaussing will be fully functional again after the monitor has been in operation for 20 minutes.

The degaussing effect is confined to the picture tube since the coils are mounted at the back of the tube. Should any part of the chassis or cabinet becomes magnetized, it is necessary to degauss the affected area with a manual degaussing coil.

5-2-7 Manual Degaussing

1. Apply line voltage to the degaussing coil and move it in a rotary motion over the front, sides, and top of the monitor. The coil should be kept away from the rear of the monitor to avoid damaging the magnetic neck components.

2. Slowly rotate and move the coil away from the monitor to about 6 feet beyond the point where no effect on the CR T will be noticeable.

For proper degaussing, it is essential that the field be gradually reduced by moving the coil slowly away from the monitor. The degaussing coil must never be shut off or disconnected while near the monitor, as this would introduce a strong field instead of canceling the effect of the stray fields.

Page 20 T roubleshooting

Page 23

6 T roubleshooting

6-1 No Raster

A1770NSL/NST

No Raster

Measure

voltage of B+ at

T402 pin 3 on

PWB-MAIN

0 V

Short Circuit

at load?

Yes

Check DC B+ line,

Q808, Q809, Q402

(68 V, 31.5 kHz)

Check voltage of

Check AC I/P

on C808

I801, Q803, R814, R813, R818, R811,

ZD807, ZD801

cathode, heater,

Grid 1, Grid 2,

Yes

Check

Normal

etc.

D801, D802,

D803, D804,

T801, R804

High

(75 V or more)

Check I401,

R858, R857,

R856, VR802

Check

T roubleshooting

Page 21

Page 24

6-2 OSD Abnormal

A1770NSL/NST

OSD Abnormal

Check I502

missing?

Check R520,

R578, R579

OK?

Yes

Check P502B

OK?

Yes

Put on

I502

Replace them

Replace it

Replace I502

Page 22 T roubleshooting

Page 25

6-3 Function Key Abnormal

Function Key Abnormal

A1770NSL/NST

Check I701 and

I703 missing?

Power

ON/OFF again and

check X701,

oscillator OK?

Yes

Check

I703 EEPROM

content OK?

Yes

Put on

I701, I703

Replace X701

Replace I703 or

do ATE again

T roubleshooting

Replace I701 and

check uP OK?

Check

pin 5 of I701

is 5V?

Replace R842, Q805

Yes

Replace I701

Check

Q703, Q704

Page 23

Page 26

6-4 No Vertical Scan (Raster is one horizontal line)

No Vertical Scan

A1770NSL/NST

Check voltage of

pin 3 is 12V, pin 7

is 50V?

Yes

Check

pin 6 O/P waveform

at I301

Normal

Check

pin 1, 2, 9 of I401

waveform

Abnormal

Ckeck or replace

I301.

Replace I301

Still no vertical scan

Check or replace CRT

Page 24 T roubleshooting

Page 27

6-5 Out of Horizontal Synchronization

Out of Horizontal

Synchronization

A1770NSL/NST

Horizontal

sync present at

pin 15 of I401

Yes

Check

I401 pin 8 H output

frequency

Yes

Check Q401, T401,

Q402, R424,

R425, D401

6-6 Out of Vertical Synchronization

Out of Vertical

Synchronization

Ckeck or replace

the signal cable

or I701

Check or

replace the

signal cable

or I701

Vertical sync

present at

pin 14 of I401

Yes

Check

I401 pin 24 ramp

frequency

Check C301

Recommended Spare Parts List

Ckeck signal cable

& vertical sync

input & I701

Page 25

Page 28

6-7 R.G.B. Video Amplifier Abnormal

RGB Video AMP Abnormal

A1770NSL/NST

Check

waveform at I501 pin 16, 19

and 22

Yes

Check

I901 pin1, 3 & 5 collector

voltage (normally about 72V)

& waveform

Yes

Video signal present at the

pin of the CRT R.G.B.

Cathode

Yes

Check or replace the

signal cable or I501

Check I901

Defective cut-off circuit

(DC restore)

Page 26 T roubleshooting

Page 29

A1770NSL/NST

7 Recommended Parts List

Note: The components identified by “ “ mark are critical for X-ray safety. Replace these with

only the same parts specified.

No. Locat ion Part Number Desc ription

1 C417 6326215442 MPP uF 0.15 250V J F P=15 HJ C

2 C808 6312622126 ALU uF 220 400V F 85C 25x40

4 D814 6412017900 DIODE RL3 3.5A/350V SANKEN 5 D815 6412004117 DIODE UF2004M T52 2A/ 400V 50nS 6 D820 6412002017 DIODE UF3004M T52 3A/400V 50nS 7 F801 6851004050 FUSE TIME LAG 5ST4 4A/250V 8 I301 6442012300 IC TDA4866 9P (PHILIPS) 9 I401 6442020700 IC TDA4854 32P SDIP (PHILIPS)

10 I501 6442021500 IC TDA4886 24P SDIP (PHILIPS)

11 I701 6448012200 IC NT68P61A 40P PDIP OTP NOVAT

12 I703 6448007900 IC 24C04A/P (MICROCHIP)

13 I801 6442006020 IC UC3842BN 8P PDIP ( ST)

14 L404 6111504130 COIL CHOKE 5mH K DR10x16 LY3B

D801 D802 D803 D804

6412011307 DIODE 1N5406 T52 3A/600V

15 L405 6119005200 COIL LINEAR TLN-1052 16 L406 6111686131 COIL CHOKE 68uH K DRWW10x16 17 L409 6111105131 COIL CHOKE L=105uH K DRWW16x18 18 Q402 6421004400 TR NPN 2SC5386 (TOSHIBA) 19 Q420 Q421 6426001800 FET N-CHNL IRFS630 TO-220F 20 Q430 Q807 6426006400 FET N- CHNL IRFS630A SAMSUNG 21 Q803 6426006800 FET N-CHNL SS S10N60A SAMSUNG 22 R403 6224211024 MF KOHM 11 1/4W F T2 6 23 R404 6224213024 MF KOHM 13 1 /4 W F T26

Recommended Spare Parts List

Page 27

Page 30

No. Location Part N umbe r De s cription

A1770NSL/NST

30 T801

31 T802

32 X701

R405 6224130114 MF KOHM 3.01 1/8W F T26 R803 6203090002 POSISTOR 9 O HM Q 2PINPITC H=10 R804 6201100012 THERMISTOR 10 OHM 3A P=7.5 TKS R818 6220327852 FS OHM 0.27 1W J HO R T401 6135000801 XFRMR HOR DRIVE THD- 1008A EI19 T402 6133070020 FBT TFB-7002 FEA766 SAMPO

6138001601 LINE FILTER TLF- 1016A 16mHET28 6131060700 XFRMER PWR TPW- 1065 EE42/15DEI 6449000710 CRYSTAL 8MHz TOP8.000 30pF TOP

Page 28 Recommended Spare Parts List

Page 31

8 Block Diagram

P501

SDA

SCL

O/R

LED

DDC I704

OSD BLK

KEY

CONTROL

S702

RGB

O/R

SDA

SCL

I501 PRE AMP TAD4886

12V

I701

NT68P61A

OSD

MTV018

ABL

I901

Video AMP

LM 2407

SDA 1

SCL 1

A1770NSL/NST

Q901

R BUFFER &

DC RESTORE

Q931

G BUFFER &

DC RESTORE

12V

B BUFFER &

DC RESTORE

BLANKING

CKT Q302

I401

TDA4854

Q961

ABL

BRIGHTNESS

CONTROL &

SPOT KILLER

DRIVER

SCL1

SDA1

V-LBL

V-TTL

OUT

H-TLB

GND

6.3V

12V

80V

145V

GND

P503

24.5KV

HFLB

-130V

570V

FBT

6.6KV 145V

DIODE

MODULATE

RESET

CKT

E2PROM

I703

LINE

FILTER

BRIGHTNESS

DEG CKT

BRIDGE

DIODE

Q805

LOW VOLTAGE

DROP DOWN

SMPS

POWER

O/P

TRANS

T802

VERTICAL

O/P I301

STEP

CKT

dynamic

foucus

I802

-H

D.Y

-V

800V

TDA4866

XRP

12.5V

Q813

Q811

80V

Block Diagram

Page 29

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