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Service Manual
17-inch Color Monitor
B1770NSLD
Service Manual Versions and Revision

N o. Ve rs i o n R e le a s e D a te R e v is io n

1. 1. 0 Sep. 1, 2000 Original release

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.
B1770NSLD Service Manual.
Printed in Taiwan.
B1770NSLD

Table of Contents

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

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

3 Control Location and Functions ........................................................................ 9

4. Operation Theory ............................................................................................10

5. Alignments and Adjustments ...........................................................................15

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

7. Recommended Spare Parts List .......................................................................26

8. Block Diagram .................................................................................................28

Page 1
B1770NSLD

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
B1770NSLD

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.

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B1770NSLD

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
B1770NSLD

2 Product Specifications

2-1 Specifications

17- inch (16- inch Visual image area), sloted mask, 90 degrees
P icture Tube deflectio n, dot type black matrix, medium short persistence
phosphor, dark tint, no n- glare/ anti- static screen,
0 . 2 5 mm p itch

VGA, S up er VGA, 1 0 2 4 x7 6 8 @ 6 0 /7 0 /7 5 /8 5 Hz,
S canning F req uency
1 2 8 0 x1 0 2 4 @ 6 0 Hz

Maximum Reso lutio n 1 2 8 0 d o ts (H) x 1 0 2 4 lines (V) @ 6 0 Hz refre sh rate

Disp lay Are a 3 0 0 mm (H) x 2 2 5 mm (V) typ ic a l

Disp lay C ha ra c te rs 8 0 c ha r. x 60 ro ws on a 10 x 10 matrix

Disp lay C o lo rs Analo g Inp ut Unlimited C o lo rs

S ynchro nizatin S ignals S ep arate S ync: ho rizo ntal/vertical, TTL, p o sitive o r negative

Ho rizo nta l : 3 0 to 7 0 k Hz
S ynchro nizatio n F req uencies
Vertic a l : 5 0 to 1 6 0 Hz

S ignal C o nne c to rs 1 5 - p in, D- she ll c onne c tor

Vid e o S ignals Ana lo g : 0 . 7 Vp - p , RGB p o sitive

P o wer Inp ut 11 0 Watts (ma ximum) AC rated vo lta ge , 1 0 0 VAC to 2 4 0 VAC

Misconvergence C enter Area : < 0.25 mm; C o rne r Are a : < 0 . 3 5 mm

P o wer O n/O ff, C o ntrast, Brightness, Ho rizo ntal S ize, Ho rizo ntal
P o sition, Vertical S ize, Vertical P o sition, Vertical Linearity
User C o ntro ls C enter, Vertical Linearity S ymmetry, P incushion, Trapezoid,
Ro tatio n, C o lo r temp erature, Language, Disp lay F req uency,
Degauss, Recall, H. Mo ire,V. Mo ire,
O S D P o sitio n

S e rvic e C o ntro ls P W B- 1 4 7 6 : R- b ia s (VR9 0 1 ), G- b ia s (VR9 3 1 ),
B- b ia s (VR9 6 1 ),
P W B- 1 4 7 8 : p o we r vo lta ge a d just (VR8 0 1 ),
high vo ltage adjust (VR401), fo cus1 , fo cus2

Preset Modes 13 (see Table 2- 2. Timing C hart)

Enviro nmental
O p eratio n temp erature : 0 o C to 4 0 o C ambient
C o nsid eratio ns
O p eratio n Humidity : 20% to 80% ambient
S torage temp erature : - 4 0 o C to 6 0 o C ambient
S to ra ge Humid ity : 5 % to 9 5 % (no n- co nd e nsing)
Altitud e : - 4 0 0 m to 3 0 0 0 m a b o ve se a level

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

Page 5
B1770NSLD

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
B1770NSLD

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

H. D ots 640 640 640 832 640 640 800 1024 800 1024 1024 1280 1024

V. D ots 400 480 480 624 480 480 600 768 600 768 768 1024 768

H-fre q (k Hz) 31.47 31.47 35 49.73 37.5 43.3 46.8 48.36 53.67 56.48 60.02 63.98 68.68

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

A pe riod us 31.78 31.78 28.57 14.32 26.666 23.111 21.333 20.68 18.63 17.71 16.66 15.63 14.56

B B lk ing us 6.356 5.72 7.407 5.59 6.35 5.33 5.172 4.923 4.409 4.053 3.657 3.778 3.725

C S ync us 3.81 3.81 2.116 1.12 2.03 1.556 1.616 2.092 1.138 1.813 1.219 1.037 1.016

D B .P. us 1.907 1.589 3.175 3.91 3.81 2.222 3.232 2.462 2.702 1.92 2.235 2.296 2.201

E Active us 25.42 25.42 21.164 20.111 20.32 17.778 16.162 15.75 14.22 13.65 13 11.852 10.836

F F.P. us 0.626 0.318 2.116 0.56 0.51 1.556 0.323 0.369 0.569 0.32 0.203 0.444 0.508

V-fre q (Hz) 70.08 59.95 66.667 74.55 75 85 75 60 85 70.07 75.03 60.02 85

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

O Pe riod ms 14.27 16.68 15 13.44 13.33 11.764 13.333 16.67 11.76 14.27 13.33 16.661 11.77

P B lk ing ms 1.557 0.922 1.286 0.865 0.533 0.67 0.533 0.786 0.578 0.673 0.533 0.656 0.582

Q S ync ms 0.064 0.064 0.086 0.06 0.08 0.069 0.064 0.124 0.056 0.106 0.05 0.047 0.044

R B .P. us 1.112 0.794 1.14 0.784 0.427 0.578 0.448 0.6 0.503 0.513 0.466 0.594 0.524

S Active us 12.71 15.25 13.714 12.55 12.8 11.093 12.8 15.88 11.18 13.6 12.8 16.005 11.18

T F.P. us 0.381 0.064 0.086 0.02 0.026 0.023 0.021 0.062 0.019 0.053 0.017 0.016 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
B1770NSLD

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 - S y nc Powe r
C o n s u mp t i o n

ON Gr e e n P ul s e P ul s e N o r ma l

S TA N D B Y Ye l l o w N o P ul s e P ul s e <1 5 w a tts

S US P E N D Ye l l o w P ul s e N o P ul s e <1 5 w a tts

OFF A mb e r N o P ul s e N o P ul s e <3 w a tts

Page 8
B1770NSLD

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. Increase Key: Scroll across main menu, highlighting control to be adjusted. Increase value of selected
control. Toggle between Contrast and Brightness adjustment screens.
3. Decrease Key: Scroll across main menu, highlighting control to be adjusted. Decrease 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 articular 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 Ajustment" mode, press (1) & (4) keys simultaneously then press (6).

Page 9
B1770NSLD

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 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, (h) Trapezoid, (i) Rotation, (j) Vertical Linearity Center, (k) Vertical Linearity
Symmetry and (l) OSD Position.
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 keys on the front panel.
4. Powerful PHILIPS TDA4856 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, (l) Full horizontal and vertical auto sync capability and (m) Vertical Linearity Center and
Symmetry - factory adjust.
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 4856 and some DAC in CPU, above operation
takes about 500 ms.
2. There allows 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 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 keys, they are detected by sensing
the voltage through R710, R740, R711, R743, R741, R742 to pin 14 and 15 of I701.

4-3 Deflection Section
1. I2C -- autosync deflection controller is TDA4856.
2. The TDA4856 is a high performance and efficient solution for autosync monitors. All functions are
controllable by I2C bus. SDA and SCL signals coming from microprocessor feed to pin 19 and pin 18 to
control all functions.
Page 10
B1770NSLD

4-3-1 Horizontal Section
1. The oscillator is driven by the currents in R467 and R468. The minimum oscillator frequency is determined
by R467 and the maximum frequency is determined by R468.
2. Horizontal sync goes into pin 15 through R494. And horizontal flyback pulse goes into pin 1 through R479
and bypass filter C446 from Emitter of Q403 and C406, C407, C415, C461, R407, cD432, R404, R402 for
AFC loop.
3. Horizontal driver (pin8) 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 14 through R313.
2. The free running frequency is determined by R314 and C312.

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. (+12.5V at pin 3, +48V at pin 7).

4-3-4 E-W/Trapezoid and H. Width Controls
1. The scan current is determined by B+ (the voltage of C410) that is obtained from step-up circuit output.
Step-up circuit include Q808, Q807, T803, D801, R829, R847.
2. I401 TDA4856 pin 6 (B DRV) will drive the step-up circuit to change H. width.
3. EW DRV (pin11) provides a complete EW drive waveform including parabola, corner and trapezoid
correction and feed to BIN (pin 5 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 divided
by R476, R477 and R478 come into pin 2 of TDA4856.
2. If this voltage is higher than 6.39 V, then TDA4856 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 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 HUNLock will send 5 V pulse to saturate Q429 and
cutoff Q420, then G1 will go down to -145V. During the mode change, Mute acts as same as HUNLock's.
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.

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B1770NSLD

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, C432, Q418, VR402, R487 and Q419 to control I501
pin 24 voltage. When I501 pin 24 voltage drops below 5V, the ABL function will happen.

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. Horizontal and vertical dynamic comes from I401 pin 32 and is amplified through C427, R450, Q416,
Q415, Q414, R498 and feed to FBT dynamic focus pins.
2. This amplifier need 700V voltage supply, it comes from FBT pin 2 and rectified through L406, D414 and
C426.

4-4 Power Supply Section

4-4-1 AC Rectifier
The circuit can accept 90 V to 264 V AC input through D808 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 R830, R831, R851, Q807, I802.
2. Normal : Green light
Amber LED is off because Q807 turned on. R830, R831 voltage is low, only green LED is turned on.
3. Standby / Suspend : Yellow light
Both of Q807 and I802 are off, then green and amber LED are turned on. That is yellow.
4. Off Mode : Amber light
I802 is on and R851 voltage is low, 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 (MC3842) gets power from R831, R830, 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 D821 auxiliary voltage.

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B1770NSLD

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 R816 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 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 9.5Vp-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 & 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, the Hunlock will keep high to pull down I402 pin 2 and shut down PWM output.

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 IC501 TDA 4886 preamplifier.
2. The amplifier RGB signals (0~3 Vpp) are adjusted by I2C bus from I501, pin 5 is for clamp pulse which
comes from pin 16 of TDA4856 to set up equal clamp level.
3. The video output stages are amplified by I901.
4. The RGB cathodes cut off are adjusted by VR910, VR940 and VR970.

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B1770NSLD

5. Under override condition, "CHECK SIGNAL" will show up on the screen.

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 R517 to I502 pin 10, and positive horizontal pulse from HFLB1 to I502 pin 5. CPU
I701 pin 27, 28 (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, 14, 13, and 12 to I501 pin 2,
3,4, and 1, then the OSD picture appears.

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B1770NSLD

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 R512-TP001 end, and adjust VR801 for 12.5 + 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. 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.

Page 15
B1770NSLD

5-2 Alignment Procedures

5-2-1 High Voltage Adjustment
CONDITION
Display image : Crosshatch pattern
PROCEDURE
Connect DC meter to TP2 and adjust VR401 to obtain a DC voltage of -145