Service Manuals, User Guides, Schematic Diagrams or docs for : LITE-ON CRT monitors B1997pns B1997
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Service Manual
19-inch Color Monitor
B1997NST
Service Manual Versions and Revision
No. Ve rsion Re le ase Date Re vision
1. 1.0 July 15, 2000 Original release
2. 1.1 July 28, 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.
B1997NST Service Manual
Printed in Taiwan.
B1997NST
Table of Contents
1. Precautions.........................................................................................................2
2. Product Specifications .......................................................................................5
3. Operation Theory............................................................................................. 10
4. Alignments and Adjustments ........................................................................... 14
5. Troubleshooting ............................................................................................... 18
6. Recommended Spare Parts List ....................................................................... 22
7. Block Diagram ................................................................................................ 24
8. Exploded Diagrams.................................................................................. Inserted
9. PCB Diagrams ......................................................................................... Inserted
10. Schematic Diagrams ................................................................................ Inserted
Page 1
B1997NST
1 Precautions
Please 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 Precautions
B1997NST
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 unconnected.
Precautions Page 3
B1997NST
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
B1997NST
2 Product Specifications
2-1 Specifications
Picture Tube 19-inch (18-inch Visual image area), 95 degrees deflection, dot type
black matrix, medi um short per sistence phosphor, dark bulb,direct
etch, Flat square screen with Invar Mask, 0.26 mm dot pitch
VGA, Super VGA, 1024x768@60/70/75/85/100 Hz,
Scanni ng Frequency
1280x1024@60/75/85 Hz, 1600x1200@60/ 75 Hz
Maximum Resoluti on 1600 dots (H) x 1200 lines (V) @75 Hz refresh rate
Display Area 360 mm (H) x 270 mm (V) typi cal
Display Characters 80 char. x 60 rows on a 10 x 10 matrix
Display Colors Analog
Unlimi ted Colors
Input
Synchr onizatin Signals Separate Sync: hor izontal/verti cal, TTL, positive or negative
Synchr onization Horizontal : 30 to 95 kHz
Frequencies Vertical : 50 to 120 Hz
Signal Connectors 15-pin, D-shell connector
Video Signals Analog : 0.7 Vp-p, RGB positi ve
Power Input 150 Watts maximum (PHILIPS CRT) AC rated voltage, 90VAC to
264VAC
Misconvergence Center Area : < 0.2 mm; Corner Area : < 0.35 mm
User Controls Power On/Off, Contrast, Brightness, Horizontal Size, Horizontal
Position, Vertical Size, Vertical Position, Pincushion, Trapezoid,
Rotation, Unbalance, Parallelogram, Degauss, Top Corner, Bottom
Corner, Recall, V. Moire, H. Moire
Service Controls PWB1498 : power voltage adjust (VR801), high voltage adjust
(VR102), F1/F2/G2 (FBT)
Preset Modes 10 (see Table 2-2. Timing Chart)
Environmental Operation temperature : 10 o C to 35 o C ambient
Considerations Humidity : 20% to 80% ambient
Storage temperatur e : -40 o C to 65 o C ambient
Storage Humidity : 10% to 90% (non-condensing)
Altitude : up to3000m above sea level
Note: Above specifications are subject to change without prior notice.
Product Specifications Page 5
B1997NST
2-2 Signal Cable Pin Connections
Table 2-1. Signal Cable Pin Assignment
Pin Signal Pin Signal
1 Red vi de o 9 +5V ( fr om PC)
2 Gr een vi deo 10 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
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.
Page 6 Product Specifications
B1997NST
2-3 Timing Chart
This section describes the timings that the computer industry recognizes as standard for computer-generated
video signals.
Table 2-2. B1997NST Timing Chart
Mode 1 2 3 4 5 6 7 8 9 10
H. Dot s 640 640 720 800 800 1024 1024 1280 1280 1600
V. Dot s 480 480 400 600 600 768 768 1024 1024 1200
H- f re q ( kHz ) 31.47 43.27 37.93 46.885 53.67 60.03 68.67 80 91.146 93.75
Sync
- - - + + + + + + +
Polarit y
A pe riod us 31.78 23.11 26.366 21.333 18.631 16.66 14.561 12.504 10.971 10.667
B Blking us 6.356 5.33 6.085 5.172 4.409 3.657 3.725 3.022 2.844 2.765
C Sync us 3.81 1.556 2.028 1.616 1.138 1.219 1.016 1.067 1.016 0.948
D B.P. us 1.907 2.22 3.042 3.232 2.702 2.235 2.201 1.837 1.422 1.501
E Ac t ive us 25.42 17.78 20.282 16.162 14.222 13 10.836 9.481 8.127 7.901
F F.P. us 0.636 1.556 1.014 0.323 0.569 0.203 0.508 0.119 0.406 0.316
V- f re q ( Hz ) 59.94 85 85.04 75 85 75.03 84.99 75 85 75
Sync
- - + + + + + + + +
Polarit y
O Pe riod ms 16.68 11.76 11.759 13.33 11.756 13.33 11.765 13.329 11.761 13.333
P Blking ms 1.43 0.67 1.213 0.533 0.578 0.533 0.582 0.525 0.527 0.533
Q Sync ms 0.064 0.069 0.079 0.064 0.056 0.05 0.044 0.038 0.033 0.032
R B.P. us 1.02 0.578 1.107 0.448 0.503 0.466 0.524 0.475 0.483 0.491
S Ac t ive us 15.25 11.09 10.546 12.8 11.179 12.8 11.183 12.804 11.235 12.8
T F. P. us 0.35 0.023 0.026 0.021 0.019 0.017 0.015 0.013 0.011 0.011
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
Product Specifications Page 7
B1997NST
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 <8 w a tts
2-6 TCO Version
The monitor meets the TCO 92, NUTEK energy saving, electric and magnetic field requirements. Also it
is compliant with TCO 95 and TCO 99 labelling scheme.
2-6-1 TCO 92
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
B1997NST
2-6-2 TCO 95
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.
Product Specifications Page 9
B1997NST
3 Operation Theory
This is an I2C-bus fully digital controlled multi-sync color monitor, compliant with VESA DDC1/2B and
DPMS standards. Besides, it also meets TCO95 and MPRII requirements. It provides user friendly OSM
(On-Screen display Menu) controls, and offers the following main features.
3-1 Main Features
1. Simplified chassis design with minimum components.
2. Fully digital controlled via 8-bit microcontroller NT6861AU.
3. Auto switching to off mode under "OUT OF RANGE" (Fh < 29KHz or Fh > 99KHz).
4. Reliable chassis design through various internal circuit protections.
5. Universal full range AC input and low power consumption.
6. Five-country OSM language available for easy user controls.
7. Adjustable OSM display time and position.
8. Twelve preset modes up to 1600 x 1200 75Hz (Fh =93.75KHz).
3-2 Microcontrol Section
1. The microcontroller provides I2C bus (pin 27 & 28) for geometric controls via I401 TDA4856 and video
controls via I501 M52743. The geometric controls include H-size, H-position, V-size, V-position, Pincushion,
Pin-balance, Trapezoid, Corner, Parallelogram, H-focus, V-focus, H-moire and V-moire. The video controls
cover Contrast, Brightness, R/G/B gain and cutoff control alignments. Through 8-bit PWM's (pin 1, 2, 3,
32, 36, 40) it provides factory controls for G1, NS-trapezoid, H-linearity, ABL, user control for Rotation
and one F/V for H-frequency driver compensation . Two I/O's (pin 27, 28) are provided for I2C bus used
for I502 MTV021N-21 on-screen display.
2. In addition, the microcontroller offers Auto Mode detection via Hsync (pin 41) and Vsync (pin 42) inputs.
According to Auto Mode detection, VESA DPMS power saving (pin 29, 30) will limit the output power
under 15W for Standby or Suspend mode, under 8W for OFF mode. VESA DPMS mode indication is
done via I/O pin 17 & 18 to drive LED display on the front cover. Normal mode displays green LED,
Standby or Suspend modes displays Yellow LED while OFF mode displays Amber LED.
3. Auto factory alignment (ATE) and VESA DDC2B communication are through DDC I2C bus (pin 27, 28),
I704 24LC211 is dedicated for DDC EDID E2PROM. In order to get optimal H-linearity performance for
the full range frequency (31KHz - 95KHz), 4-channel CS are used at pin 20, 21, 22, 23, 24. F1, F2, UP
and DOWN function keys' scanning are through 2 ADCs on pin 14 & 15. Q701 and Q702 delay circuits
are used for power-on reset at pin 4. In order to avoid I2C interference during H-size, H-position, V-size,
V-position, Contrast and Brightness alignments, the HUNLK from I401 TDA4856 is applied from Q703
inverter to IRQ at pin 16.
4. There are 12 factory preset modes and 8 user modes available. Related information data of those modes
are stored at 2 EEPROM's (I702, I703) 24LC04.
3-3 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
Page 10 Operation Theory
B1997NST
controllable by I2C bus. SDA and SCL signals coming from microprocessor feed to pin 19 and pin 18 to
control all functions.
3-3-1 Horizontal Section
1. The oscillator is driven by the currents in R424 and R423. The minimum oscillator frequency is determined
by R424 and the maximum frequency is determined by R423.
2. Horizontal sync goes into pin 15 through R314. And horizontal flyback pulse goes into pin 1 through C455,
C437, R404, C458, R40E and bypass filter C401 from Vcp of Q424 collector for AFC loop.
3-3-2 Horizontal O/P Section
1. Horizontal driver (pin8) signal is sent to Q402 via R496, C451.
2. Signal from Q427 direct drive T403, through R493 (shunt with R4A4, R40F, R40G) and L405 to horizontal
output transistor Q424.
3-3-3 Vertical Section
1. Vertical sync signal from micro controller is connected to pin 14 through R313.
2. The free running frequency is determined by R319 and C312.
3-3-4 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 TDA8351.
2. The TDA8351 has two output stages which are current driven in opposite phase and operate in combination
with the deflection coil in a full bridge configuration.
3-3-5 E-W/Trapezoid and H. Size Controls
1. The B+ driver for step down circuit is from pin 6, it provides 20~80% duty cycle outputs according
to H-frequency.
2. The E/W / Trapezoid and H-size controls are through B+ modulation at I401 TDA4856. The EW output
signal is from pin 11, it's not tracking with H-frequency.
3-3-6 X-Ray Protection
1. To avoid X-ray hazard, a DC voltage generated at pin 3 of FBT and rectified by D108, C121 is divided by
R126, R129 and C402 filter go into pin 2 of TDA4856.
2. If this voltage is higher than 6.39 V, then TDA4856 will be activated to float HUNLOCK (pin 17), H. DRV
( pin 8), B DRV (pin 6), VOUT1 (pin 12), VOUT2 (pin 13). After that all deflection circuit stop working.
3-3-7 G1, Blanking and Brightness
1. The vertical blanking signal comes in two ways. One is from pin 8 of I301 (TDA8351), the other is from
HUNLK (pin 17 of I401). These two positive vertical pulses through Q42A, Q42C, Q42E amplified and
converted into negative pulse and sent to G1 for vertical blanking.
Operation Theory Page 11
B1997NST
2. In protection mode or out-of-range situation, HUNLock will send 5 V pulse to saturate Q706, then pin 8 of
I902 will be low state and open Q509, so 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 27 and pin 28 comes into pin 20 and pin 21 of I501, DC level can
be changed by I2C bus from 0~5V of D/A output at pin 23 of I501, high voltage causes high current to get
brighter raster, low voltage gets lower brightness.
3-4 Power Supply Section
3-4-1 AC Rectifier
The circuit can accept 90 V to 264 V AC input through D801 bridge diode and C810 filtering to get DC 126
V~364 V for power conversion in T805.
3-4-2 Line Filter
It consists of C803, C804, C805, C806, C807, C871, C80A, C80C, C80E, T801 and T802 and meets EMI
regulation.
3-4-3 Power LED Status
1. The LED has 3 leads common cathode with green and amber color for different power saving states. It is
controlled by CPU.
2. Normal : Green light
Amber LED is off because CPU pin 17 is high and pin 18 is low, only green LED is turned on.
3. Standby / Suspend : Yellow light
CPU pin 17 and pin 18 are low, then green and amber LED are turned on. That is yellow.
4. Off Mode : Amber light
CPU pin 18 is high and pin 17 is low, then green is off and amber is on.
3-4-4 Auto Degaussing
When SMPS works, the 6.6 V power source is applied to Q801 and CPU let Q801 turn on a few seconds,
then drive the armature of RL801 to perform the degaussing function.
3-4-5 PWM Control
1. Start Up
The I802 gets power from C874, C841, R834, ZD807, D802, C859, R806 and pin 7 voltage reaches 9 V
for starting up. The I802 starts oscillation at 20 kHz, sawtooth on pin 4 and pin 6 output to drive Q802/
T805. Once Q802 switches on, D812, C840 set up an 17 V to keep I802 working through D828 auxiliary
voltage.
2. Regulation
The DC O/P voltage is proportional to the auxiliary voltage, so I802 pin 2 senses the feedback voltage from
the divider R895, R888, R868, R897 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.
Page 12 Operation Theory
B1997NST
3-4-6 Synchronization
1. Normal Mode
The sync pulse from FBT (31 kHz~93.75 kHz) via R820, C833, D806, R818 and C832 to pin 4 of I802 to
keep I802 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 R817 and C832 and the
SMPS works at 20 kHz.
3. Override
The horizontal free run frequency is about 62 kHz under override condition, SMPS is synchronized to this
frequency.
3-4-7 O.V.P.
If the auxiliary voltage is higher than zener voltage ZD806 (22 volts) and makes pin 3 of I802 higher than
1 V, pin 6 duty cycle is limited to have the OVP activated.
3-4-8 O.P.P.
The excess current of T805 through R819 can develop enough voltage on pin 3 then limit the power delivered
because the pin 6 duty cycle is limited too.
3-5 HV Supply
1. HV (High Voltage) start up is triggered by H-pls at pin 4 via R107. I103 3843 provides the PWM output
control (pin 6) to drive the step up B+ supplier Q103 via D105 and C108.
2. The time constant is dependent on the H-DRIVER through R140 via inverter I101 and buffer Q106 /Q107
to drive Q104.
3. I401 pin 32 provides the H+V composite signals to drive the two-stage dynamic focus amplifier. Output
of vertical amplitude is around 150 Vpp, while output of horizontal amplitude is around 670 Vpp.
Vertical dynamic focus Horizontal dynamic focus
3-6 Video Amplifier Section
1. RGB signal inputs are terminated by R501, R531 and R561 then pass through the coupling capacitors
C502, C532 and C562 to I501 M52743BSP preamplifier.
2. The amplifier RGB signals (0~3 Vpp) are adjusted by I2C bus, pin 19 is for clamp pulse which comes from
pin 16 of TDA4856 to set up equal clamp level.
3. The video output stages is I901 LM2402, the output resistors R904, R934 and R964 are 47 ohm, R913,
R943 and R973 are 56 ohm for arcing protection and the power dissipation is minimized.
4. The RGB cathodes cut off are adjusted by D/A output pins 24, 25, 26 of I501.
Operation Theory Page 13
B1997NST
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 = 93.75 kHz, FV = 75 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 2250 or equivalent)
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 (1600 x 1200 @ 93.75Khz / 75 Hz) / crosshatch pattern to the monitor.
3. Connect a DC voltage meter to D820, Heat Sink and adjust VR801 for 17.5 ◦ Jabse Service Manual Search 2026 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo