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Service Manual
15-inch Color Monitor
C1570MNSL/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 Aug. 30, 2001 O riginal release
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.
C1570MNSL/T Service Manual.
Printed in Taiwan.
C1570MNSL/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
C1570MNSL/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
C1570MNSL/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 2121 VDC
b) Test duration : 3 seconds
c) Cutoff current should be set to 10 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
C1570MNSL/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
C1570MNSL/T
2 Product Specifications
2-1 Specifications
1 5 - inc h (1 3 . 8 - inc h Visua l ima ge a re a ), s lo te d ma s k , 9 0 d e gre e s
P ic ture Tub e d e fle c tio n, d o t typ e b la c k ma trix, me d ium sho rt p e rs iste nc e
p ho s p ho r, d a rk tint, no n- gla re / a nti- s ta tic sc re e n, mini- ne c k gun
0 . 2 8 mm d o t p itc h
S c a nning F re q ue nc y VGA, S up e r VGA, 1 0 2 4 x7 6 8 @ 6 0 /7 0 /7 2 /7 5 /8 5 Hz
M a ximum Re s o lutio n 1 2 8 0 d o ts (H) x 1 0 2 4 line s (V) @ 6 0 Hz re fre s h ra te
Dis p la y Are a 2 6 2 mm (H) x 1 9 6 mm (V) typ ic a l
Dis p la y C ha ra c te rs 8 0 c ha r. x 6 0 ro ws o n a 1 0 x 1 0 ma trix
Dis p la y C o lo rs Ana lo g
Unlimite d C o lo rs
Inp ut
S ync hro niza tin S igna ls S e p a ra te S ync : ho rizo nta l/ve rtic a l, TTL, p o s itive o r ne ga tive
S ync hro niza tio n Ho rizo nta l : 3 0 to 6 9 k Hz
F re q ue nc ie s Ve rtic a l : 5 0 to 1 2 0 Hz
S igna l C o nne c to rs 1 5 - p in, D- she ll c o nne c to r
Vid e o S igna ls Ana lo g : 0 . 7 Vp - p , RGB p o sitive
P o we r Inp ut 7 5 Wa tts (ma ximum) AC ra te d vo lta ge , 1 0 0 VAC to 2 4 0 VAC
M is c o nve rge nc e C e nte r Are a : < 0 . 3 mm; C o rne r Are a : < 0 . 4 mm
Use r C o ntro ls P o we r O n/O ff, C o ntra st, Brightne s s , Ho rizo nta l S ize , Ho rizo nta l
P o s itio n, Ve rtic a l S ize , Ve rtic a l P o s itio n, P inc ushio n, Tra p e zo id ,
Ro ta tio n, C o lo r te mp e ra ture , La ngua ge , Dis p la y F re q ue nc y,
De ga us s, Re c a ll, H. M o ire ,
V. M o ire
S e rvic e C o ntro ls P W B- 1 6 0 3 : p o we r vo lta ge a d jus t (VR8 0 1 ), high vo lta ge a d just,
F o c us a d just F BT o n up VR.
To a d just R- b ia s , G- b ia s, B- b ia s , High vo lta ge a nd ABL, must
e nte r the fa c to ry mo d e .
P re s e t M o d e s 1 0 (s e e Ta b le 2 - 2 . Timing C ha rt)
Enviro nme nta l O p e ra tio n te mp e ra ture : 5 o C to 4 0 o C a mb ie nt
C o nsid e ra tio ns O p e ra tio n Humid ity : 2 0 % to 9 0 % a mb ie nt
S to ra ge te mp e ra ture : - 4 0 o C to 6 5 o C a mb ie nt
S to ra ge Humid ity : 1 0 % to 9 0 % (no n- c o nd e ns ing)
Altitud e : up to 1 0 0 0 0 fe e t a b o ve se a le ve l
Note: Above specifications are subject to change without prior notice.
Product Specifications Page 5
C1570MNSL/T
2-2 Signal Cable Pin Connections
Table 2-1. Signal Cable Pin Assignment
Pin S ig na l Pin S ig na l
1 Re d vid e o 9** +5V
2 Gre e n vid e o 10 Digita l Gro und
3 Blue vid e o 11 Gro und
4 Gro und 12 S DA
5* NC 13 H- S ync
6 Re d gro und 14 V- S ync
7 Gre e n gro und 15 SCL
8 Blue gro und
Note * This pin is used for selftest detection. Connect this pin to ground at the PC end.
** For PC 99: This pin will obtain +5V from PC side.
Page 6 Product Specifications
C1570MNSL/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 ode 1 2 3 4 5 6 7 8 9 10
H . D o ts 720 640 800 640 640 800 1024 800 1024 1024
V. D o t s 400 480 600 480 480 600 768 600 768 768
H -fre q (k H z) 3 1 .4 7 3 1 .4 7 3 7 .8 8 3 7 .5 4 3 .3 4 6 .8 4 8 .3 6 5 3 .6 7 6 0 .0 2 6 8 .6 8
S y n c P o la rity - - + - - + - + + +
A p e rio d us 3 1 .7 8 3 1 .7 8 2 6 .4 2 6 .6 6 6 2 3 .111 2 1 .3 3 3 2 0 .6 8 1 8 .6 3 1 6 .6 6 1 4 .5 6
B B lk ing us 6 .3 5 6 6 .3 5 6 6 .4 6 .3 5 5 .3 3 5 .1 7 2 4 .9 2 3 4 .4 0 9 3 .6 5 7 3 .7 2 5
C S ync us 3 .8 1 3 .8 1 3 .2 2 .0 7 1 .5 5 6 1 .6 1 6 2 .0 9 2 1 .1 3 8 1 .2 1 9 1 .0 1 6
D B .P. us 1 .9 0 7 1 .9 0 7 2 .2 3 .8 1 2 .2 2 2 3 .2 3 2 2 .4 6 2 2 .7 0 2 2 .2 3 5 2 .2 0 1
E A c tiv e us 2 5 .4 2 2 5 .4 2 20 2 0 .3 2 1 7 .7 7 8 1 6 .1 6 2 1 5 .7 5 1 4 .2 2 13 1 0 .8 3 6
F F.P. u s 0 .6 3 6 0 .6 3 6 1 0 .5 1 1 .5 5 6 0 .3 2 3 0 .3 6 9 0 .5 6 9 0 .2 0 3 0 .5 0 8
V -fre q (H z) 7 0 .0 8 5 9 .9 5 6 0 .3 2 75 85 75 60 85 7 5 .0 3 85
S y n c P o la rity + - + - - + - + + +
O P e rio d m s 1 4 .2 7 1 6 .6 8 1 6 .5 8 1 3 .3 3 11 .7 6 4 1 3 .3 3 3 1 6 .6 7 11 .7 6 1 3 .3 3 11 .7 7
P B lk ing m s 1 .5 5 7 1 .4 3 0 .7 3 9 0 .5 3 3 0 .6 7 0 .5 3 3 0 .7 8 6 0 .5 7 8 0 .5 3 3 0 .5 8 2
Q S y nc ms 0 .0 6 4 0 .0 6 4 0 .1 0 6 0 .0 8 0 .0 6 9 0 .0 6 4 0 .1 2 4 0 .0 5 6 0 .0 5 0 .0 4 4
R B .P. us 1 .0 8 1 .0 2 0 .6 0 7 0 .4 0 7 0 .5 7 8 0 .4 4 8 0 .6 0 .5 0 3 0 .4 6 6 0 .5 2 4
S A c tiv e us 1 2 .7 1 1 5 .2 5 1 5 .8 4 1 2 .8 11 .0 9 3 1 2 .8 1 5 .8 8 11 .1 8 1 2 .8 11 .1 8
T F.P. u s 0 .4 1 3 0 .3 5 0 .0 2 6 0 .0 2 6 0 .0 2 3 0 .0 2 1 0 .0 6 2 0 .0 1 9 0 .0 1 7 0 .0 1 5
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
C1570MNSL/T
2-4 Power Saving Function
Note: The monitor will be driven into Power Saving mode by the control signal from the display
controller, as indicated by the amber-color power LED.
Table 2-3. Power Saving Function
S ta te Po we r LE D
Co ns umptio n Lig ht
ON N ormal* Green
Active O F F <5 watts Amber
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
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
Page 8 Product Specifications
C1570MNSL/T
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
C1570MNSL/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 MTV212M32 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
OFF mode, (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 MAX. 14 factory preset modes and offers 8 user modes. There are 16 function icons at
OSD. They are controlled by 1 2 keys on front panel.
4. Powerful PHILIPS TDA4863AJ 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 HF < = 29 kHz and HF > = 70 kHz.
6. Full range AC input and simplified line filter design.
3-2 Microcontrol Section
1. This monitor uses MYSON MTV212M32 CPU. It contains a 8051 8-bit CPU core, 512 bytes of RAM
used as working RAM and stack area, 32k bytes of ROM, 14-channel 8 bit PWM D/A converter, 3-
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 EEPROM I703 and transfer to device 4841 and some DAC in CPU,
above operation takes about 500 ms.
2. There allowed MAX. 14 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. C1570MNSL/T Communication Protocal
3.1Monitor Communication Summary
The monitor operates the communication channel in two modes, the Transmit-Only Mode and the Bi-
Directional Mode.
3.2 Transmit-Only Mode
Like DDC1 is a uni-directional channel from display to host, the device transmits data bits on the SDA pin
in response to a clock signal on the VCLK pin.
3.3Bi-Directional Mode
It is a bi-directional channel between the display and host based on I2C protocol.
In this protocol, 2 wires (SDA-serial data, SCL-serial clock) carry information between the devices
Page 10 Operation Theory
C1570MNSL/T
connected to the bus, a device that sends data on the bus is defined to be the transmitter, and a device that
receives data from the bus is defined to be the receiver. The bus must be controlled by a master device
that generates the clock (SCL), controls access to the bus and generates the START and STOP conditions,
while the monitor acts as the slave. Data on the I2C bus can be transferred at a rate up to 100KHz.
There are two communicaionts on the monitor in I2C bus.
* DDC2 mode - The Transmission from the host to the monitor which is a request by reading the EDID.
* ATE mode - The transmission from the host to the monitor which is sending or reading the data of the
device of monitor.
* Note: The devices slave address on I2C
Device Slave address on I2C
24C08 A0H
MTV021 7AH
LM1267 DCh
TDA4841 8Ch
MCU C6h
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.
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.
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.
Operation Theory Page 11
C1570MNSL/T
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 7 and pin 6 of TDA4863AJ.
2. The TDA48634J has one output stages which are current driven in opposite phase and operate in combination
with the deflection coil in a half bridge configuration.
3. This IC is powered by two voltage. (+12V at pin 1, -12V at pin 4).
3-3-4 E-W/Trapezoid and H. Width Controls
1. The horizontal O/P stage uses diode modulator D419, D410, 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 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 2 of I301 (TDA4863AJ), the other is
from vertical sync (pin 34 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 saturate Q407, then G1
will go down to -140V. During the mode change, Mute acts as same as HUNLocks.
3. The brightness is controlled by CPU pin 39 through PNP transistor Q407. The lower control voltage
causes Q407 conducts darken to get lighter raster and a higher control voltage causes Q407 conducts
lighter to get lower brightness.
4. The brightness is controled by I701 through I2C bus to I501 (LM1267).
3-3-7 Contrast Section
1. Contrast is controlled by I701 through I2C bus to I501 (LM1267) directly.
2. Beam current is detected through T402 (FBT) pin 7, C429, R460, D406 and detected voltage feeding into
Q406, D415, Q409, R530, R532, R454, R471, C529 to control I501 pin 22 voltage. When I501 pin 24
voltage drops below 3.9V, the ABL function will happen.
3-3-8 H/V size breathing compensation
1. Beam current is sensed as above section (4-3-7 item 2) and this voltage routes through R436, Q409,
Page 12 Operation Theory
C1570MNSL/T
R459 then through R418 to I401 pin 31 for H. size compensation, 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.
Horizontal dynamic comes from C413 through R435, C450, T403, R434, C448 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 D828~D831 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 C859, C860, C803, C816, C848, C852, C807 and T801 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 31 is 1.96V and pin 30 is 0.02V, only green LED is turned on.
3. Off Mode : Amber light
CPU pin 31 is 0.02V and pin 30 is 1.92V, 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
The I801 (MC3842) gets power from R807, R873, C812 and pin 7 voltage reaches 16 V for starting up.
The I801 starts oscillation at 22 kHz, sawtooth on pin 4 and pin 6 output to drive Q803/T802. Once Q803
switching on, D806, C804 set up an 15 V to keep I801 working through D808 auxiliary voltage.
2. Regulation
The DC O/P voltage is proportional to the auxiliary voltage, so I801 pin 2 senses the feedback voltage from
the divider R802, R823, VR801 and R821 to compare with the built-in 2.5 volts reference voltage for error
amplifier operation. Finally pin 6 can modulate the different duty cycle by VR801 setting to achieve
regulation purpose.
3-4-6 Synchronization
1. Normal Mode
Operation Theory Page 13
C1570MNSL/T
The sync pulse from FBT (31 kHz~69 kHz) via C815, R826, D824, C814 and R816 to pin 4 of I801 to
keep I801 synchronized with horizontal sync input frequency.
2. Power Saving Modes: Standby/Suspend
Because there is no pulse from FBT, so the free-run frequency is decided by R815 and C814 and the
SMPS works at 22 kHz.
3. Override
The horizontal free run frequency is about 62.5 kHz under override condition, SMPS is synchronized to
this frequency.
3-4-7 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.
3-4-8 O.P.P.
The excess current of T802 through Q803, R813 and R814 can develop enough voltage on pin 3 then limit the
power delivered because the pin 6 duty cycle is limited too.
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 55 volts from T802 pin 11 via L811, D813, C824 and the gate control of Q807 comes
from I401 pin 6 via Q808, R4C9 and R855. The duty cycle is controlled by C843, C841, C846, R846, R877
and R856, R857, R839 and D821 combination ratio.
2. The regulation and boost up (from 68 V to 160 V or more, on demand). The H.V. is set at 24.5 kV (zero
beam) by CPU pin 33. The booster comprises Q807, L802, L801, D820, C425 and T802 to offer the
required B+ for different frequency modes.
3-5 Video Amplifier Section
1. RGB signal inputs are terminated by R507, R537 and R567 then pass through the coupling capacitors
C501, C531 and C561 to I501 LM1267 preamplifier.
2. The amplifier RGB signals (0~3 Vpp) are adjusted by I2C bus from 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 I701 through I2C bus.
5. Under override condition, NO SIGNAL will show up on the screen.
3-6 OSD (On Screen Display) Circuit
1. The I504 HTV021-21 is OSD IC. The OSD signals are worked by positive vertical pulse from I701 pin 34
that goes to I504 pin 10, and positive horizontal pulse from T402 pin 6 goes through R472, C419, D433 to
I504 pin 5. CPU I701 pin 12, 13 (I2C bus) transfers information to I504 pin 7, 8.
2. The OSD R. G. B signals and blanking signal are terminated at I504 pin 15, 14, 13, and 12 to I501 pin 1,
2, 3, and 4, then the OSD picture appears.
Page 14 Operation Theory
C1570MNSL/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 12