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Service Manual
17-inch Color Monitor
A1770NSL/NST
Service Manual Versions and Revision
No. Ve rsion Re le as e Date Re vision
1. 1.0 July 17, 1998 Original release
Copyright Trademarks
Copyright 1998 LiteOn Technology Corp. LiteOn is a registered trademark of LiteOn
Technology Corp.
All Rights Reserved
All other trademarks are the property of their
This manual may not, in whole or in part, be
respective owners.
copied, photocopied, reproduced, translated, or
converted to any electronic or machine readable
form without prior written permission of LiteOn
Technology Corp.
A1770NSL/NST Service Manual.
Printed in Taiwan.
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
Page 1
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 nonmetallic control knobs, insulating materials,
cabinet backs, adjustment and compartment
covers or shields, isolation resistor-capacitor
1-1-1 Warnings networks, mechanical insulators, etc.
1. For safety purpose, do not attempt to modify 3. AC Leakage Current Check
the circuit board, and always disconnect the AC Always perform the AC Leakage Current
power before performing servicing on the Check on the exposed metal parts, including
monitor. metal cabinets, screwheads and control shafts,
2. Operation of the monitor outside its cabinet or as follows:
with the cover removed involves the risk of a) Plug the AC line cord directly into a rated
shock hazard. Repair work on the monitor AC outlet. Do not use an isolation
should only be attempted by service personnel transformer during the check.
who are thoroughly familiar with all necessary
b) Use an AC voltmeter with at least 5000
safety precautions and procedures for working
ohms per volt sensitivity as follows:
on high voltage equipment.
Connect a 1500 ohms, 10 watt resistor
3. Do not lift the CRT by the neck. After
paralleled by a 0.15uF AC capacitor in series
completely discharging the high voltage anode,
with all exposed metal cabinet parts and a
handle the CRT only when wearing shatterproof
known earth ground, such as electrical
goggles. Try to keep the CRT away from the
conduct or electrical ground connected to
body during handling.
earth ground, as shown in the Figure 1-1.
4. High voltage should always be kept at the rated Measure the AC voltage across the
value, no higher. Only when high voltage is combination of resistor and capacitor.
excessive are X-rays capable of penetrating the
shell of the CRT. Operation at high voltages Figure 1-1. Set Up For AC Leakage Current Check
may also cause failure of the CRT or high
voltage circuitry.
5. The CRT is especially constructed to limit X-
ray emission to 0.5mR/HR at 300 microamperes
anode current. To ensure continued X-ray
protection, replace the CRT with only the same To kn ow n To ex pos ed m e tal
ca bin et part
or equivalent type as the original, and adjust the earth g ro und
0.15 ufd
anode's voltage to the designated maximum
rating, never to exceed.
15 00 o hm 1 0 w att
1-1-2 Safety Checks
Before returning the monitor to the user, perform
c) Reverse the AC plug at the AC outlet and
the following safety checks:
repeat the steps for AC voltage
1. Inspect to make certain that each lead dress is measurements for each exposed metal part.
not pinched or that hardware is not lodged
d) Voltage reading must not exceed 0.3 volts
between the chassis and other metal parts in
RMS, equivalent to 0.2 milliampere AC. Any
the monitor.
value exceeding this limit ill constitute a
2. Inspect all protective devices such as potential shock hazard and must be
corrected immediately.
Page 2 Precautions
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 Page 3
A1770NSL/NST
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.
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.
Page 4 Precautions
A1770NSL/NST
2 Product Specifications
2-1 Specifications
17- i nc h ( 15.8- i nch Vi s ua l i ma ge a r e a ) , s l ote d ma s k, 90
Pi c tur e Tube de gr e es de fl e c ti on, dot type bl ac k ma tr i x, me di um s hor t
pe r s i s te nc e phos phor, da rk ti nt, non-gl a r e / a nti - s ta ti c s c r e en,
0. 27 mm dot pi tc h
VGA, Supe r VGA, 1024x768@60/ 70/ 75/ 85 Hz,
Sc a nni ng Fr e que nc y
1280x1024@60 Hz
Ma xi mum Re sol uti on 1280 dots ( H) x 1024 l i ne s ( V) @60Hz r e fre s h ra te
Di s pl ay Ar e a 300 mm ( H) x 225 mm ( V) typi c a l
Di s pl ay Cha r a c te r s 80 c har. x 60 row s on a 10 x 10 ma tr i x
Di s pl ay Col or s Ana l og
Unl i mi te d Col ors
Input
Sync hr oni za ti n Si gna l s Se pa r a te Sync : hor i zonta l / ve r ti c a l , TTL, pos i ti ve or ne ga ti ve
Sync hr oni za ti on Hor i zonta l : 30 to 69 kHz
Fr e que nci e s Ve r ti c a l : 55 to 120 Hz
Si gna l Conne c tor s 15- pi n, D- s he l l c onne c tor
Vi de o S i gna l s Ana l og : 0.7 Vp- p, RGB pos i ti ve
Pow er Input 95 Wa tts ( ma xi mum) AC ra te d vol ta ge , 100VAC to 240VAC
Mi s c onve r genc e Ce nte r Ar e a : < 0.3 mm; Cor ne r Ar e a : < 0.4mm
Pow er On/ Off, Contra s t, Br i ghtne s s, Hor i zonta l Si ze ,
Hor i zonta l Pos i ti on, Ver ti c a l Si ze , Ve r ti c a l Pos i ti on,
Us e r Contr ol s
Pi nc ushi on, Tr a pe zoi d, Rota ti on, Col or te mpe r a tur e ,
La ngua ge , Di s pl a y Fre que nc y, De ga us s , Re c a l l , H. Moi r e ,
V. Moi re
Se r vi c e Control s PWB- 1410 : R- bi a s ( VR910) , G-bi a s ( VR940),
B- bi a s ( VR970) ,
PWB- 1440 : pow e r vol ta ge a dj us t ( VR801) ,
hi gh vol ta ge a dj us t ( VR802) , foc us 1, foc us 2
Pr e s e t Mode s 13 (s e e Ta bl e 2- 2. Ti mi ng Char t)
Envi r onme nta l
Ope r a ti on te mpe ra tur e : 5 o C to 40 o C a mbi e nt
Cons i de ra ti ons
Ope r a ti on Humi di ty : 20% to 80% a mbi e nt
Stora ge te mpe ra tur e : -40 o C to 65 o C a mbi e nt
Stora ge Humi di ty : 5% to 95% ( non-c onde ns i ng)
Al ti tude : up to3000m a bove s e a l e ve l
Note: Above specifications are subject to change without prior notice.
Product Specifications Page 5
A1770NSL/NST
2-2 Signal Cable Pin Connections
Table 2-1. Signal Cable Pin Assignments
Pin Signal Pin Signal
1 Red video 9 NC
2 Green video 10 Digital Gr ound
3 Bl ue video 11 Ground
4 Ground 12 SDA
5 NC 13 H-Sync
6 Red ground 14 V- Sync/ VCL
7 Green gr ound 15 SCL
8 Bl ue ground
Note: This pin is used for selftest detection. Connect this pin to ground at the PC end.
Page 6 Product Specifications
A1770NSL/NST
2-3 Timing Chart
This section describes the timings that the computer industry recognizes as standard for computer-generated
video signals.
Table 2-2. Timing Chart
M o de 1 2 3 4 5 6 7 8 9 10 11 12 13
H. D o ts 720 640 640 800 640 640 800 1024 800 1024 1024 1280 1024
V. D o ts 400 480 480 600 480 480 600 768 600 768 768 1024 768
H-fre q (k Hz) 31.47 31.47 35 37.88 37.5 43.3 46.8 48.36 53.67 56.48 60.02 64.34 68.68
S y nc Po la rity - - - + - - + + + + + + +
A pe rio d us 31.78 31.78 28.57 26.4 26.666 23.111 21.333 20.68 18.63 17.71 16.66 15.55 14.56
B B lk ing 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 y nc 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
17.77- 10.83-
E Ac tiv e us 25.42 25.42 21.164 20 20.32 16.162 15.75 14.22 13.65 13 11.96
8 6
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-fre q (Hz) 70.08 59.95 66.667 60.32 75 85 75 60 85 70.07 75.03 60 85
S y nc Po la rity + - - + - - + + + + + + +
O Pe rio d ms 14.27 16.68 15 16.58 13.33 11.764 13.333 16.67 11.76 14.27 13.33 16.67 11.77
P B lk ing 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 S y 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
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 Ac tiv e us 12.71 15.25 13.714 15.84 12.8 11.093 12.8 15.88 11.18 13.6 12.8 16.03 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
S ep erate Sy nc
K
H o riz o n t a l E Ve rtic a l
B H
V id e o V id e o
D F J L
S y nc S y nc
C A I G
H.Parameters: V.Parameters:
A: Period B: Blanking Time G: Period H: Blanking Time
C: Sync Width D: Back Porch I: Sync Width J: Back Porch
E: Active Time F: Front Porch K: Active Time L: Front Porch
Product Specifications Page 7
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) .
Table 2-3. Display Power Management Signal (DPMS)
Sta te LED Co lor H-Sy nc V-Sy nc Po we r
Co ns umptio n
ON Green Pulse Pulse N ormal
STAN DBY Yello w N o Pulse Pulse <1 5 watts
SUS PEN D Yello w Pulse N o Pulse <1 5 watts
O FF Amb er N o Pulse N o Pulse <8 watts
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 Testing, commonly known as MPR 1990 recommendations. These limits are
summarized in the Table 2-4.
Table 2-4. TCO 92 Requirements
VL F /T C O E L F /T C O
M a g n e t ic F ie ld 2 5 nT 2 0 0 nT
E le c t r ic F ie ld 1 V/m 1 0 V/m
F r e q ue nc y R a nge 2 ~ 4 0 0 k Hz 5 ~ 2 0 0 0 Hz
Va lu e RM S RM S
D is t a n c e 30 cm 30 cm
E le c t r o s t a t ic
+ /- 5 0 0 V + /- 5 0 0 V
P o t e n t ia l
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.
Page 8 Product Specifications
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 Technical 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
Fe a t ur e St a nda r d D e s c r ip t io n
L in e a r it y 1 % o r le s s D if f e r e n c e in le n g t h o f c o lu mn s o r r o w s c o mp a r e d t o t h e
c o r r e s p o n d in g le n g t h s t h r o u g h t h e c e n t e r o f t h e mo n it o r .
D is p la y L u min a n c e 1 0 0 c d / m2 ( a t le a s t )
L u min a n c e 1 . 7 :1 o r le s s T h e r a t io is b e t w e e n t h e ma x t o min lu min a n c e w it h in t h e
U n if o r mit y w h o le a c t iv e a r e a .
Product Specifications Page 9
A1770NSL/NST
3 Control Location and Functions
(1) Function Key
(2) Decrease Key
(3) Increase Key
(4) Select Key
(5) Power LED
(6) Power ON/OFF
(1) (2) (3) (4) (5) (6)
3-1 Front Panel
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
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 I2C BUS controlled geometric correction, contrast and
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.
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) I2C 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 1 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) X-
ray 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 ATE 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 1 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 I2C bus. SDA and SCL signals come from microprocessor feed to pin 19 and pin 18 to
control all functions.
Operation Theory Page 11
A1770NSL/NST
4-3-1 Horizontal 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. Vertical 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/Trapezoid and H. Width Controls
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+ minus Vm ( the voltage of C418) values and the pincushion control
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.
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
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 : Yellow 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
A1770NSL/NST
4-4-4 Auto 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
A1770NSL/NST
4-5 Video 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 2C bus from I501, pin 5 is for clamp pulse which
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.
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
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
5-1-1 Adjustment 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 ATE 1 at power off condition.
2. Press both 1 key and 2 key simultaneously then power on.
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.
Page 16 Alignments and Adjustments
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