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Service Manual
17-inch Color Monitor
C1770NSL/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 May 4, 2001 O riginal release
2. 1.1 Aug. 10, 2001 append section
5- 8 Blank EEPRO M Trouble- shooting
Copyright Trademarks
Copyright 2001 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.
C1770NSL/T Service Manual.
Printed in Taiwan.
C1770NSL/T
Table of Contents
1. Precautions.........................................................................................................2
2. Product Specifications .......................................................................................5
3. Operation Theory............................................................................................. 10
4. Alignments and Adjustments ........................................................................... 15
5. Troubleshooting ...............................................................................................19
6. Recommended Spare Parts List .......................................................................25
7. Block Diagram .................................................................................................27
8. Exploded Diagrams.................................................................................. Inserted
9. PCB Diagrams ......................................................................................... Inserted
11. Schematic Diagrams ................................................................................ Inserted
Page 1
C1770NSL/T
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
or equivalent type as the original, and adjust the ea rth g ro un d ca bin et p art
0.15 ufd
anodes 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 Precautions
C1770NSL/T
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 instruments ground lead to the instrument chassis ground before connecting the
positive lead; always remove the instruments 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
C1770NSL/T
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
C1770NSL/T
2 Product Specifications
2-1 Specifications
1 7 - inch (16 - inch Visual image area), slo ted mask , 9 0 d egrees
P icture Tub e d eflection, d o t typ e b lack matrix, medium sho rt p ersistence
p hosp ho r, d ark tint, no n- glare/ anti- static screen,
0 .2 8 mm d o t p itch
VGA, S uper VGA, 1 0 24 x7 6 8@ 6 0 /7 0 /7 5 /8 5 Hz
S canning F req uency
1 2 80 x1 0 24 @ 60 Hz
Maximum Reso lutio n 1 2 80 do ts (H) x 1 0 2 4 lines (V) @ 6 0Hz refresh rate
Disp lay Area 3 0 6 mm (H) x 2 3 0 mm (V) typ ical
Disp lay C haracters 8 0 char. x 60 ro ws on a 1 0 x 10 matrix
Disp lay C o lors Analo g
Unlimited C o lo rs
Input
S ynchro nizatin S ignals S ep arate S ync: ho rizontal/vertical, TTL, po sitive or negative
S ynchro nizatio n Ho rizo ntal : 3 0 to 7 0 k Hz
F requencies Vertical : 5 0 to 1 6 0 Hz
S ignal C onnecto rs 1 5 - p in, D- shell co nnecto r
Video S ignals Analog : 0 .7 Vp- p , RGB p o sitive
P o wer Inp ut 7 5 Watts (maximum) AC rated vo ltage, 1 00 VAC to 2 40 VAC
Misco nvergence C enter Area : < 0. 3 mm; C orner Area : < 0. 4 mm
User C o ntro ls P o wer O n/O ff, C o ntrast, Brightness, Ho rizo ntal S ize, Ho rizo ntal
P o sitio n, Vertical S ize, Vertical P o sitio n, P incushio n, Trap ezo id ,
Ro tatio n, C o lo r temp erature, Language, Disp lay F requency,
Degauss, Recall, H. Mo ire,
V. Mo ire
S ervice C ontrols P W B- 1 5 52
P W B- 1 5 63 : p ower voltage adjust (VR8 0 1), high vo ltage ad just
P reset Mo d es 8 (see Table 2 - 2 . Timing C hart)
Enviro nmental O p eratio n temp erature : 1 0 o C to 4 0 o C amb ient
C o nsid eratio ns O p eratio n Humidity : 2 0% to 8 0 % ambient
S torage temp erature : - 4 0 o C to 6 5 o C amb ient
S torage Humid ity : 1 0 % to 90 % (non- co ndensing)
Altitud e : N on o perating 4 0 ,0 0 0 feet sea level
o p erating 10 , 00 0 feet sea level
Note: Above specifications are subject to change without prior notice.
Product Specifications Page 5
C1770NSL/T
2-2 Signal Cable Pin Connections
Table 2-1. Signal Cable Pin Assignment
Pin S ig na l Pin Sig na l
1 Red vi de o 9** +5V
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 PC 99: This pin will provide +5V from PC side.
Page 6 Product Specifications
C1770NSL/T
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
H. D o ts 640 640 640 800 800 1024 1280 1024
V. D o ts 480 480 480 600 600 768 1024 768
H-fre q (k Hz) 31.47 37.5 43.3 46.8 53.67 60.02 63.98 68.68
S y nc Po la rity - - - + + + + +
A pe rio d us 31.78 26.666 23.111 21.333 18.63 16.66 15.63 14.56
B B la nk ing us 6.356 6.35 5.33 5.172 4.409 3.657 3.778 3.725
C S y nc us 3.81 2.03 1.556 1.616 1.138 1.219 1.037 1.016
D B .P. us 1.907 3.81 2.222 3.232 2.702 2.235 2.296 2.201
E Activ e us 25.42 20.32 17.778 16.162 14.22 13 11.852 10.836
F F.P. us 0.636 0.51 1.556 0.323 0.569 0.203 0.444 0.508
V-fre q (Hz) 59.95 75 85 75 85 75.03 60 85
S y nc Po la rity - - - + + + + +
O Pe rio d ms 16.68 13.33 11.764 13.333 11.76 13.33 16.661 11.77
P B lank ing ms 1.43 0.533 0.67 0.533 0.578 0.533 0.656 0.582
Q S y nc ms 0.064 0.08 0.069 0.064 0.056 0.05 0.047 0.044
R B .P. us 1.02 0.427 0.578 0.448 0.503 0.466 0.594 0.524
S Activ e us 15.25 12.8 11.093 12.8 11.18 12.8 16.005 11.18
T F.P. us 0.35 0.026 0.023 0.021 0.019 0.017 0.016 0.015
Seperate Sync
Horizontal E Vertical K
B H
Video Video
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
Product Specifications Page 7
C1770NSL/T
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)
S ta te LED Co lo r H-S y nc V-S y nc Po we r
Co ns umptio n
ON Gre en P ulse P ulse N o rmal*
OFF Amb e r N o P ulse P ulse < 5 watts
OFF Amb e r P ulse N o P ulse < 5 watts
OFF Amb e r N o P ulse N o P ulse < 5 watts
* For power consumption : 75W Max. (@ 230V AC, preset size and maximum light output condition)
2-5 TCO Version (Optional)
The monitor meets the TCO 95/99, NUTEK energy saving, electric and magnetic field requirements.
Also it is compliant with TCO 95/TCO 99 labelling scheme.
The emission from magnetic and electric field must comply with the limits specified by the Swedish Board
for Measurement and Testing, commonly known as MPR 1990 recommendations. These limits are sum-
marized in the Table 2-4.
Table 2-4. TCO 95 Emission 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
Page 8 Product Specifications
C1770NSL/T
same routing scheme is used when doing CRT replacement.
2-5-1 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 .
2-5-2 TCO 99 Version (Optional)
TCO 99 will append the color temperature and energy efficiency specification, also cover the environmental
requirement.
Product Specifications Page 9
C1770NSL/T
3 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.
3-1 Main Features
1. Simplified design with minimum components.
2. The MYSON MTV212 M(A) 32 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 10 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 TDA4863 and TDA4841 present the following useful functions: (a) Pincushion, (b)
Trapezoid, (c) V-Position, (d) V-Size, (e) Verticals C and S correction -- factory adjust, (f) Pincushions
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 > = 70 kHz.
6. Full range AC input and simplified line filter design.
3-2 Microcontrol Section
1. This monitor uses MYSON MTV212 M(A) 32 CPU. It contains a 8051 8-bit CPU core, 256 bytes of
RAM used as working RAM and stack area, 32k bytes of OTP ROM, 13-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 4841 and some DAC
in CPU, above operation takes about 500 ms.
2. There allowed 8 factory preset modes and 8 user modes. There are 11 functions, Contrast, Brightness, H.
Size, H. Position, V. Size, V. Position, Pincushion, and Trapezoid, Rotation, H. Moire, V Moire, all controlled
by OSD icon which can be adjusted by user.
3. The pin 27 and pin 28 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, R741, R743, R716, R717 to pin 25 and 26 of I701.
3-3 Deflection Section
1. I2C -- autosync deflection controller is TDA4841.
2. The TDA4841 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 Operation Theory
C1770NSL/T
3-3-1 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 goes into pin 15 through R318. And horizontal flyback pulse goes into pin 1 through R401
and bypass filter C403 from pin 6 of FBT and R496 for HFLB loop.
3. Horizontal driver (pin8) O/P to Q401 via C410.
3-3-2 Vertical Section
1. Vertical sync goes into pin 14 through R317.
2. The free running frequency is determined by R301 and C301.
3-3-3 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 TDA4863.
2. The TDA4863 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 and one set of negative voltage. (+12V at pin 1, -12V
at pin 4, +35V at pin 2).
3-3-4 E-W/Trapezoid and H. Width Controls
1. The horizontal O/P stage uses diode modulator D419, D433, 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 TDA4841.
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.
3-3-5 X-Ray Protection
1. To avoid X-ray hazard, a DC voltage generated at pin 6 of FBT and rectified by D408, C432 and divided
by R403, R404 and R405 come into pin 2 of TDA4841.
2. If this voltage is higher than 6.39 V, then TDA4841 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.
3-3-6 G1, Blanking and Brightness
1. The vertical blanking signal comes from two ways. One is from pin 8 of I301 (TDA4863), the other is
from vertical sync (pin 32 of I701). These two positive vertical pulses through Q405 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 cutoff Q407, then G1
will go down to -150V. During the mode change, Mute acts as same as HUNLocks.
3-3-7 Contrast Section
1. Contrast is controlled by I701 through I 2C bus to I501 (LM1267) directly.
2. Beam current is detected through T402 (FBT) pin 7, C429, R449 and detected voltage feeding into Q432,
Operation Theory Page 11
C1770NSL/T
Q433, R436, R497, R459, C482 to control I501 pin 22 voltage. When I501 pin 22 voltage drops
below 4.1 V, the ABL function will happen.
3-3-8 H/V size breathing compensation
1. Beam current is sensed as above section (3-3-7 item 2) and this voltage routes through R451, R468, C470
then through R437 to I401 pin 31 for H. size compensation.
2. HV voltage is detected through T402(FBT) pin 11. C481, R4F4, R4F8, R4F9, Q428, R4G0, Q431, R4G1,
then through R302 to I401 pin 21 for V. size compensation.
3-3-9 Dynamic focus circuitry
The dynamic focus is applied to improve the corner focus performance, it includes horizontal and vertical
dynamic focus.
1. Horizontal dynamic comes from C413 through R435, C450, T401, R434, C448 and feed to FBT dynamic
focus pin (T401 pin 12).
2. Vertical dynamic comes from I401 pin 32 through C315, R322, R326, R321, R323, Q301, R324, R325 and
feed to FBT dynamic focus pin.
3-4 Power Supply Section
3-4-1 AC Rectifier
The circuit can accept 90 V to 264 V AC input through D801~D803 bridge diodes and C808 filtering to get
DC 126 V~364 V for power conversion in T802.
3-4-2 Line Filter
It consists of C803, T801, C804, C805, C808, C819, C807, C817 and meets EMI regulation.
3-4-3 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 30 is 1.96V and pin 31 is 0.45V, only green LED is turned on.
3. Off Mode : Amber light
CPU pin 30 is 1.87V and pin 31 is 0.46V, then green is off and amber is illuminated.
3-4-4 Auto Degaussing
When S801 turns on, pin 14 of I701 will send a signal to Q802 and turns on RL801 for degaussing. After 4
seconds, it will turn off RL801 automatically.
3-4-5 PWM Control
1. Start Up
Page 12 Operation Theory
C1770NSL/T
The I801 (5S0765C) gets power from R807, R808, C830 and pin 3 voltage reaches 15 V for starting up.
The I801 starts oscillation at 20 kHz, pin 1 output to drive T802. Switching on, R819 set up an 15 V to
keep I801 working through D809 auxiliary voltage.
2. Regulation
The DC O/P voltage is proportional to the auxiliary voltage, so I801 pin 4 senses the feedback voltage
from the divider D806, R809, C810, VR801, Q803, Q801 and R821 to compare with the built-in 1.5 volts
reference voltage for error amplifier operation. Finally pin 6 can modulate the different duty cycle by
VR801 setting to achieve regulation purpose.
3-4-6 Synchronization
1. Normal Mode
The sync pulse from FBT (31 kHz~69 kHz) via R812, R811 and C815 to pin 5 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 SMPS works at 20 kHz by I801 itself.
3. Override
The horizontal free run frequency is about 63.2 kHz under override condition, SMPS is synchronized to
this frequency.
3-4-7 O.V.P.
If the auxiliary voltage is higher than 25 volts makes pin 3 of I801 is limited to have the OVP activated.
3-4-8 O.P.P.
The excess current of T802 through I801 pin 1, 2, make Vs>1.1V internal of I801, then limite the power.
3-4-9 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 58 volts from T802 pin 10 via L811, D813, C824 and the gate control of Q451 comes
from I401 pin 6 via Q450, Q434, D435 and R4E5. The duty cycle is controlled by I701 pin 33 (PWM pin
Adj.) via R719, C741, R4F6, R4F5, R4F1.
2. The regulation and boost up (from 68 V to 160 V or more, on demand). The H.V. is set at 25.6 kV (zero
beam) by I301 pin 33 which senses the secondary O/P from FBT. The booster comprises Q451, L410,
L411, D450, C425 and T802 to offer the required B+ for different frequency modes.
3-5 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 LM1267 preamplifier.
2. The amplifier RGB signals (0~3 Vpp) are adjusted by I2C bus, I501 pin 23 is for clamp pulse which comes
from pin 16 of TDA4841 to set up equal clamp level.
3. The video output stages are amplified by I502 (LM2469).
4. The RGB cathodes cut off are adjusted by I503 (LM2479) pin 8, 7, 6, which comes from I501 pin 16, 15,
14 to adjust cut iff voltage level by I2C bus.
Operation Theory Page 13
C1770NSL/T
5. Under override condition, NO SIGNAL will show up on the screen.
3-6 OSD (On Screen Display) Circuit
1. The I504 MTV021-21 is OSD IC. The OSD signals are worked by positive vertical pulse from I701 pin
34 that goes through R720 to I502 pin 10, and positive horizontal pulse from T402 pin 5 goes through R496
to I502 pin 5. CPU I701 pin 13, 12 (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 1,
2, 3 and 4 then the OSD picture appears.
Page 14 Operation Theory
C1770NSL/T
4 Alignments and Adjustments
This section of the service manual explains how to make permanent adjustments to the monitor settings.
4-1 General Adjustments
4-1-1 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 = 68.68 kHz, FV = 85 Hz, unless otherwise
defined.
4-1-2 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
4-1-3 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 VGA (1024 x 768 @ 68.68 kHz/85 Hz) signal to the monitor.
3. Connect a DC voltage meter to TP001 (on the Main board), and adjust VR801 for 11.7