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Service Manual
17-inch Color Monitor
S1770NSL/T
Service Manual Versions and Revision
N o. Ve rs ion R e le as e D ate R e vis ion
1. 1.0 June 19, 2000 Original release
2. 1.1 Aug. 8, 2000 P. 12, 16, 18, 24, 28, 29
3 1.2 Aug. 16, 2000 P. 13 4-4-3
P. 17 5-2-2
Copyright Trademarks
Copyright 2000 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.
S1770NSL/NST Service Manual.
Printed in Taiwan.
S1770NSL/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
S1770NSL/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 ta l
ca bin et p art
or equivalent type as the original, and adjust the ea rth g ro un d
0.15 ufd
anode's voltage to the designated maximum
rating, never to exceed.
1500 ohm 10 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
S1770NSL/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.
Page 3
S1770NSL/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
S1770NSL/NST
2 Product Specifications
2-1 Specifications
1 7 - i nc h ( 1 5 . 8 - i nc h Vi s ua l i ma ge a r e a) , s l o te d ma s k, 9 0
Pi c tur e Tub e
d e gr e e s d e fl e c ti o n, d o t typ e b l a ck ma tr i x, me d i um s ho r t
p e r s i s te nc e p ho s p ho r, d a r k ti nt, no n- gl a r e / a nti - s ta ti c s c r ee n
VGA, Sup e r VGA, 1 0 2 4 x7 6 8 @6 0 / 7 0 / 7 5 / 8 5 Hz,
Sc a nni ng Fr e q ue nc y
1 2 8 0 x1 0 2 4 @6 0 Hz
Ma xi mum Re s o l uti o n 1 2 8 0 d o ts ( H) x 1 0 2 4 l i ne s ( V) @6 0 Hz r efr e s h r a te
Di s p l a y Ar e a 3 0 0 mm ( H) x 2 2 5 mm ( V) typ i c a l
Di s p l a y Cha r a c te r s 8 0 c ha r. x 6 0 r o w s o n a 1 0 x 1 0 ma tr i x
Di s p l a y Co l o r s Ana l o g
Unl i mi te d Co l o r s
Inp ut
Sync hr o ni za ti n Si gna l s Se p a r a te S ync : ho r i zo nta l / v er ti c a l , TTL, p o s i ti v e o r nega ti v e
Sync hr o ni za ti o n Ho r i zo nta l : 3 0 to 7 0 kHz
Fr eq ue nc i e s Ve r ti c a l : 5 0 to 1 6 0 Hz
Si gna l Co nne cto r s 1 5 - p i n, D- s he l l co nne c to r
Vi d e o Si gna l s Ana l o g : 0 . 7 Vp - p , RGB p o s i ti v e
Po w e r Inp ut 1 0 0 Wa tts ( ma xi mum) AC r ated v o l ta ge , 1 0 0 VAC to 2 4 0 VAC
Mi s c o nv e r ge nce Ce nte r Ar e a : < 0 .3 mm; Co r ne r Ar e a : < 0 . 4 mm
Po w e r On/ Off, Co ntr a s t, Br i ghtne s s , Ho r i zo nta l Si ze ,
Ho r i zo nta l Po s i ti o n, Ve r ti ca l Si ze , Ver ti c a l Po s i ti o n,
Us e r Co ntr o l s
Pi nc us hi on, Tr a p e zoi d, Ro tati on, Co l o r te mp e r a tur e ,
La ngua ge , Di s p l a y Fr e q ue nc y, De ga us s , Re c a l l , H. Mo i r e ,
V. Mo i r e
Se r v i c e Co ntr o l s PWB- 1 5 2 6 : R- b i a s ( VR9 0 1 ) , G- b i a s ( VR9 3 1 ) ,
B- b i a s ( VR9 6 1 ) ,
PWB- 1 5 1 9 / 1 5 3 9 : p o w e r v o l ta ge a d j us t ( VR8 0 1 ) ,
hi gh v o l ta ge a d j us t ( VR4 0 1 ) , fo c us 1 , fo c us 2
Pr e s e t Mo d e s 1 3 ( s e e Tab l e 2 - 2 . Ti mi ng Cha r t)
Env i r o nme nta l
Op er a ti o n temp e r a tur e : 5 o C to 4 0 o C a mb i ent
Co ns i d e r ati o ns
Op e r a ti o n Humi d i ty : 2 0 % to 8 0 % a mb i e nt
Sto r a ge te mp e r atur e : - 4 0 o C to 6 5 o C a mb i ent
Sto r a ge Humi d i ty : 5 % to 9 5 % ( no n- co nd e ns i ng)
Al ti tud e : up to 3 0 0 0 m a b o v e s e a l ev e l
Note: Above specifications are subject to change without prior notice.
Page 5
S1770NSL/NST
2-2 Signal Cable Pin Connections
Table 2-1. Signal Cable Pin Assignment
Pin Signal Pin Signal
1 Red vi de o 9** PC
2 Gr een vi deo 10 Di gi tal Gr ound
3 Bl ue vi de o 11 Gr ound
4 Gr ound 12 SDA
5* NC 13 H- Sync
6 Red gr ound 14 V- Sync / VCL
7 Gr een gr ound 15 SCL
8 Bl ue gr ound
Note: * This pin is used for selftest detection. Connect this pin to ground at the PC end.
** For PC99 : this pin will provide +5V from PC side.
Page 6
S1770NSL/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. Dots 720 640 640 800 640 640 800 1024 800 1024 1024 1280 1024
V. D o t s 400 480 480 600 480 480 600 768 600 768 768 1024 768
H - f re q ( k H z ) 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
- - - + - - + - + - + + +
P o la rit y
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 2.03 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 A c t iv e us 25.42 25.42 21.164 20 20.32 17.778 16.162 15.75 14.22 13.65 13 11.96 10.836
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 - f re q ( H z ) 70.08 59.95 66.667 60.32 75 85 75 60 85 70.07 75.03 60 85
S y nc
+ - - + - - + - + - + + +
P o la rit y
O P e 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 0.427 0.578 0.448 0.6 0.503 0.513 0.466 0.501 0.524
S A c t iv 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 era te S y n c
K
H o rizo n tal E Vertic al
B H
Vid e o Vid e o
D F J L
Sync Sync
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
Page 7
S1770NSL/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)
State LED Co lo r H- S y nc V- Sy nc Po we r
Co ns umpt io n
ON Gr e e n P ul s e P ul s e No r ma l
S TANDBY Ye l l o w No P ul s e P ul s e <1 5 w a tts
S US P END Ye l l o w P ul s e No P ul s e <1 5 w a tts
OF F Amb e r No P ul s e No P ul s e <5 w a tts
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/TCO 99 labelling scheme.
2-6-1 TCO 92 Version (Optional)
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 when doing CRT replacement.
Page 8
S1770NSL/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 .
2-6-3 TCO 99 Version (Optional)
TCO 99 will append the color temperature specification.
Page 9
S1770NSL/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.
3. To select a user control, press (2) or (3) key repeatedly until the control is highlighted.
4. To adjust the value for a 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.
Note: To enter the "Internal Adjustment" mode, press (1) & (4) keys simultaneously then press (6).
Page 10
S1770NSL/NST
4 Operation Theory
This is a fully digital controlled multi-sync color monitor that is compliant with DDC1/2B Plug and Play VESA
standard and offers the following main features.
4-1 Main Features
1. Simplified design with minimum components.
2. The NOVATEK NT68P61AU processor-- that has I2C bus and PWM function 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 switching for linearity and size compensation.
3. Stores up to 14 factory preset modes and offers 7 user modes. There are 16 function icons in OSD. They
are controlled by 1 2 keys on the front panel.
4. Powerful SAMSUNG KB2512 and NS LM1279AN 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 (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 > = 73 kHz.
6. Full range AC input and simplified line filter design.
4-2 Microcontrol Section
1. This monitor uses NOVATEK NT68P61AU 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
41 and pin 42, 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 KB2512 and some DAC in CPU, above
operation takes about 500 ms.
2. There allows 14 factory preset modes and 7 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 25 and pin 26 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, R743, R741 to pin 14 and 15 of I701.
4-3 Deflection Section
1. I2C -- autosync deflection controller is KB2512.
2. The KB2512 is a high performance and efficient solution for autosync monitors. All functions are controllable
by I2C bus and PWM port. SDA and SCL signals coming from microprocessor feed to pin 31 and pin 30 to
control all functions.
Page 11
S1770NSL/NST
4-3-1 Horizontal Section
1. The oscillator is driven by the currents in R471. The oscillator frequency is determined by R471 and C449.
2. Horizontal sync goes into pin 1 through R422. And horizontal flyback pulse goes into pin 12 through Q438
and bypass filter C457 from Emitter of Q403 and C406, C407, C461, R407, D432, R404, R402 for AFC
loop.
3. Horizontal driver (pin 26) output to Q401 via C403, Q401 switching to drive T401 provide IB1/IB2
current then turn on/off Q402 and switching the yoke current.
4-3-2 Vertical Section
1. Vertical sync goes into pin 2 through R448.
2. The free running frequency is determined by C438.
4-3-3 Vertical O/P section
1. The differential output currents from pin 23 of I401 can be directly coupled to the vertical deflection
booster pin 1 of TDA8172.
2. The TDA8172 operate in combination with the deflection coil in a half bridge configuration.
3. This IC is powered by two sets of voltages. (+11.5V at pin 2, -11.5V at pin 4).
4-3-4 E-W/Trapezoid and H. Width Controls
1. The scan current is determined by B+ (the voltage of C470) that is obtained from step-up circuit output.
Step-up circuit include Q405, R414, T403, D407, R411, R412.
2. I401 KB2512 pin 28 (B DRV) will drive the step-up circuit to change H. width.
3. EW DRV (pin 24) provides a complete EW drive waveform including parabola, corner and trapezoid
correction and feed to BIN (pin 15 of I401) to get a good control for pincushion / trapezoid / corner.
4. The top and bottom corner correction can be adjusted seperately.
4-3-5 X-Ray Protection
1. To avoid X-ray hazard, a DC voltage generated at pin 6 of FBT and rectified by D417, C431 and go
through R855, Q823 and ZD802 come into base of Q816 to control 12V switch transistor Q813.
2. If anode voltage is higher than 29KV, Q813 will be activated through Q816. 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 6 of I301 (TDA8172), the other is
from vertical sync (pin 33 of I701). These two positive vertical pulses through Q421 amplified and converted
into negative pulse and sent to G1 for vertical blanking.
2. In protection mode or an out-of- range situation, the mute will send 5 V pulse to saturate Q429 and cutoff
Q420, then G1 will go down to -130V.
3. The brightness is controlled by CPU pin 3 through PNP transistor Q420. Q420 is a switch in conducted
(ON) status normally. The lower or higher control voltage will get low brightness or high brightness.
4-3-7 Contrast Section
Page 12
S1770NSL/NST
1. Contrast is controlled by I701 through pin 32 PWM to I501 (LM1279AN) directly.
2. Beam current is detected through T402 (FBT) pin 7, C432, Q418, VR402, R453, Q419 and detected
voltage feeding into R505 to control I501 pin 10 voltage.
4-3-8 Dynamic focus circuitry
The dynamic focus is applied to improve the corner focus performance, it includes horizontal and vertical
dynamic focus.
1. Vertical dynamic comes from I401 pin 10 and is amplified through C427, R450, Q414, R498 and feed to
FBT dynamic focus pins.
2. This amplifier need 200V voltage supply, it comes from FBT pin 2 and rectified through L406, D414 and
C426.
3. Horizontal dynamic comes from T405 through C476, R446 and feed to FBT dynamic focus pins.
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, C820, C823, 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
states. It is controlled by CPU.
2. Normal : Green light
Amber LED is off because CPU pin 18 is low nd pin 17 is high, only green LED is turned on.
3. Standby / Suspend : Yellow light
CPU pin 17 and pin 18 are high, then green and amber LED are turned on. That is yellow.
4. Off Mode : Amber light
CPU pin 17 is low and pin 18 is high, then green is off and amber is illuminated.
4-4-4 Auto Degaussing
When S801 turns on, pin 10 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 (MC3843) gets power from R847, R848, C806 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 D821 auxiliary voltage.
2. Regulation
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The DC O/P voltage is proportional to the auxiliary voltage, so I801 pin 2 senses the feedback voltage
from the divider R802, R823 and VR801 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 R816 and C814 and the
feedback voltage change by Q822 and Q820, they are controlled by I805 and I806.
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 High Voltage Generation with F.B.T.
1. The H. V generation circuit combines T402 F.B.T. with I402 TL494/KA7500 PWM control circuit.
2. When I402 Vcc(pin12) reaches at 5V, pin 5,6 gets a freerun sawtooth waveform about 25KHz, and
approximately 9.5 Vp-p, when voltage at pin 15 is higher than pin 16 (5V reference) then release pin 3 to be
controlled by pin 1 feedback signal and compare with pin 5 to output PWM.
3. HFLB1 is used to trigger pin 5 via Q412, to synchronize the deflection circuit.
4. PWM output will drive Q411 and T402 to gererate high voltage (25KV), T402 pin 11, 12 becomes DC/
AC feedback, with the voltage link to I402 non-inverting input pin 1 to stabilize H.V (25KV) and VR401
can be adjusted to control H.V value.
5. When X.R.P occur, Q813 will switch off the 12V for I402 and shut down PWM output.
4-5 Video Amplifier Section
1. RGB signal inputs are terminated by R525, R526 and R527 then pass through the coupling capacitors
C502, C504 and C506 to IC501 LM1279AN preamplifier.
2. The amplifier RGB signals (0~3 Vpp) are adjusted by I2C bus from I501, pin 11 is for clamp pulse which
comes from pin 34 of I701 to set up equal clamp level.
3. The video output stages are amplified by Q963, Q964, Q903, Q904, Q933, Q934, Q962, Q965 Q902,
Q905, Q932, Q935.4. The RGB cathodes cut off are adjusted by VR961, VR901 and VR931.
5. Under override condition, "CHECK SIGNAL" will show up on the screen.
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4-6 OSD (On Screen Display) Circuit
1. The I502 HTV021-02 is OSD IC. The OSD signals are worked by positive vertical pulse from I701 pin 32
that goes through R521 to I502 pin 10, and positive horizontal pulse from HFLB1 through R513 to I502
pin 5. CPU I701 pin 27, 28 (I 2C bus) transfers information to I502 pin 7, 8.
2. The OSD R. G. B signals and blanking signal are terminated at I502 pin 15, 14, 13, and 12 to I501 pin 2,
3,4, and 1, then the OSD picture appears.
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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 = 68 kHz, FV = 85 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 R428-TP001 end, and adjust VR801 for 11.5 + 0.2/-0 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. Press both 1 key and 2 key simultaneously then power ON.
2. After turn the power off, monitor will go back to normal mode.
3. When you use ATE adjustment fixture, you should switch S705 to ATE (Factory) position, after you
finish the adjustment, please switch S705 to DDC (normal) position to return to normal mode.
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5-2 Alignment Procedures
5-2-1 High Voltage Adjustment
CONDITION
Display image : Crosshatch pattern
PROCEDURE
Connect DC meter to TP5 and adjust VR401 to obtain a DC voltage of -134