Acer AL1702 Schematic
Service Manual
17-inch LCD Monitor
AL1702
Service Manual Versions and Revision
No.VersionRelease DateRevision
1.1.0May 12, 2004Original release
Copyright
Copyright 2004 LiteOn Technology Corp.
All Rights Reserved
This manual may not, in whole or in part, be
copied, photocopied, reproduced, translated, or
converted to any electronic or machine readable
form without prior written permission of LiteOn
Technology Corp.
ACER AL1702 Service Manual.
Printed in Taiwan.
Trademarks
LiteOn is a registered trademark of LiteOn
Technology Corp.
All other trademarks are the property of their
respective owners.
AL1702
1) Circuit Description
1.Power Board Operation Therory--------------------------------------------------------------------------------------------3
2.Inverter--------------------------------------------------------------------------------------------------------------------------4
3.Interface-------------------------------------------------------------------------------------------------------------------------5
3.1 Top---------------------------------------------------------------------------------------------------------------------------5
3.2 Power------------------------------------------------------------------------------------------------------------------------5
3.3 VGA & DDC interface-----------------------------------------------------------------------------------------------------5
3.4 Scaler MST8111A---------------------------------------------------------------------------------------------------------5
3.5 Panel interface--------------------------------------------------------------------------------------------------------------5
3.6 Audio------------------------------------------------------------------------------------------------------------------------7
4.Others---------------------------------------------------------------------------------------------------------------------------7
4.1 Detection of POWER switch status------------------------------------------------------------------------------------7
4.2 Display mode identification----------------------------------------------------------------------------------------------7
4.3 Power ON sequence------------------------------------------------------------------------------------------------------8
4.4 Power OFF sequence-----------------------------------------------------------------------------------------------------8
4.5List of I/O Pin Assignments of the I307--------------------------------------------------------------------------------9
2) Trouble Shooting
1.No display of screen (Screen is black, color of LED is amber)--------------------------------------------------------11
2.Nothing displays on screen (Screen is black, color of LED is green)------------------------------------------------12
3.Checking the back light unit-----------------------------------------------------------------------------------------------15
4.Abnormal screen-------------------------------------------------------------------------------------------------------------16
Page 1
AL1702
6.Abnormal plug and play operation---------------------------------------------------------------------------------------18
7.Checking the interface circuit of sync signal----------------------------------------------------------------------------19
7.1 Checking the control circuit of horizontal sync pulse-------------------------------------------------------------19
7.2 Checking the control circuit of vertical sync pulse----------------------------------------------------------------19
8Checking the resolution change IC movement--------------------------------------------------------------------------20
9.Checking the DC/DC converter circuit-----------------------------------------------------------------------------------21
10.Checking the Audio circuit [option]--------------------------------------------------------------------------------------22
11.Checking inverter board circuit--------------------------------------------------------------------------------------------23
12.Power board------------------------------------------------------------------------------------------------------------------24
3) Spare Parts
Recommended Spare Parts List-------------------------------------------------------------------------------------------------25
Page 2
AL1702
1) Circuit Description
1.Power Board Operation
1.1Line filter consists of C801, T801, C802, C803, C804. It eliminates high frequency interference to meet EMI’s
requirement.
1.2Rec & Filter
Bridge diode D801 converts AC source into pulsed DC. This pulsed DC is smoothed and filtered by C805.
R802 is an NTC ( negative thermal coefficient ) resistor, used to reduce inrush current to be within safe range.
1.3Power transformer :
T802 converts energy for square wave from power source C805 to secondary side to generate +12V and +22V.
1.4Output :
The square wave from T802 is rectified by D809, D811, then filtered by C822, C817 to generate +12V and +22V
respectively. I804 is the regulator for +5V output.
1.5Driver :
Q803 drive T802 from PWM control of I801 for power converted.
1.6FB :
Negative feedback CKT consists of photo coupler I802 and adjustable regulator I803. It can maintain output
voltages +22V and +12V at a stable level.
1.7PWM :
1.7.1Start : When power is turned on, Q801 conducts due to bias from C805 and R805,R803. C807 is charged a
16 volt and a starting current about 0.3mA to pin 7 of I801. I801 starts to oscillate and outputs a pulse
train through pin 6 to drive Q803.
1.7.2OPP : When Q803 turns on, C805 supplies a linearly increasing triangle current through the primary
inductance of T802 to the driver Q803, once the peak value of this current multiplied by R811 exceeds1
volt, pulse train will be turn off immediately to protect Q803, T802 from being burned out.
1.7.3Regulation : If output voltage +22V or 12V goes up, the R terminal of I803 gets more bias, accordingly
photo transistor and photo diode flows more current. The voltage of pin 2 of I801 goes up too, making
the pulse width of pin 6 of I801 to become narrower. So the output voltage +5V will be pulled down to a
stable value.
1.7.4OVP : If +22V or 12V goes up too much, the induced voltage on pin 4 of T802 becomes large also.
Suppose that it is over 18 volts, ZD801 conducts, pin 3 of I801 is pulled up over 1 volt. The pulse train at
pin 6 of I801 goes down to zero, shutting Q803 off immediately.
1.7.5SCP : If output terminal is short to ground, photo transistor does not conduct, hence Q806 does not
conduct either. Then oscillation of I801 is stop, shutting Q803 off immediately.
Power Board Block Diagram
Line
Filter
Rec. &
Filter
PWM Driver
Power
Transformer
FB
Outpur Rec. & Filter
Page 3
AL1702
2.Inverter Operation
This unit operates on an output voltage of 22V from power source.
2.1VCC: When On/Off pin of P802 is high level input, Q106 turns on and provides +5VDC for I101 power supply.
2.2Control IC: I101 (OZ960S)
2.2.1Enable : When pin 3 of I101 is over 1.5V, I101 works. If it is under 1.5V, I101 turns off.
2.2.2OSC: When I101 enabled, R108/C115 (pin 17/pin18 of I101) determine the operating frequency.
2.2.3SST: C104 (pin 4 of I101) provides soft start function.
2.2.4Ignition: R109 (pin 8 of I101) provides higher operating frequency for more striking voltage until regula-
tion of feedback of lamp current. C103 (pin 1 of I101) determine the striking time.
2.2.5Dimming control: The divided voltage of R106/R105/R104 control the duty pulse of burst-mode to drive
Q105 and perform a wide dimming control for the CCFL. The burst-mode frequency is determined by C116.
2.2.6Regulation: Pin 9/pin 10 of I101 provide regulation of the CCFL current from feedback. The non-inverting
reference (pin 10 of I101) is at 1.25V nominal.
2.3Protection: Open-lamp protection in the ignition period is provided through both pin1 and pin 2 of I101 to ensure
a rated voltage is achieved and a required timing is satisfied.
Removal of the CCFL during normal operation will trigger the current amplifier (pin 9/pin 10 of I101) output and
shuts off the inverter. This is latch function.
2.4
2.4.1Output drivers: The configuration prevents any shoot-through issue associated with bridge-type power
conversion applications. Adjusting the overlap conduction between I102 P-MOSFET and I103 N-MOSFET,
I101 N-MOSFET and I103 P-MOSFET, the CCFL current regulation is achieved.
2.4.2Full-bridge switching/Transformer: I102/I103 /C123/T101 compose full-bridge switching to convert DC
into AC for driver the CCFL.
2.5Detection: C128/C129/C132/D115/D114/C118 detect the output voltage and ensure a rated voltage by pin2 of
I101.
2.6Feedback: D116/D117/R120/D108/R116 sense the lamp current for negative feedback and regulation. The divided
voltage on R116 will be at 1.25V.
Inverter Circuit Block Diagram
VCC
ON / OFF
Brightness
control
Regulator
U.V.P. Enable
OSC
SST
Dimming
control
VDD
Control IC : OZ960
Output driver
Protection
Ignition
Regulation
Full-bridge switching
Transformer
Detection
Feed back
Lamp
Page 4
3.Interface Operation
3.1Top (Circuit diagrams MAIN PWB 2 of 8)
This page is function block. (1) power. (2) VGA & DDC interface. (3) scaler MST8111B. (4) panel interface. (5)
audio (option).
3.2Power (Circuit diagrams MAIN PWB 3 of 8)
3.2.1P301 connector
A 5V power supply for LCD module, MCU, logic. And a 12V power supply for audio function. It is
generated from the P301 connector.
3.2.2I301 : 3-terminal regulator
A 2.5V power supply for scaler IC I305, it is generated from the 5V source.
3.2.3I302 : 3-terminal regulator
A 3.3V power supply for scaler I305, it is generated from the 5V source.
3.2.4Q303, I312 : ON/OFF control for LCD module power
ON/OFF control (PANELVCC_EN) is performed for power ON/OFF and also for the power saving
sequence.
3.2.5R306 : ON/OFF control for LCD module back light power
ON/OFF control (BKLT_EN) is performed for black light power ON/OFF and also for the power saving
sequence.
3.2.6Q301,Q302 : Adjust back light luminance for LCD module
It is adjusted back light luminance control (BKLT_ADJ) is performed for the back light luminance.
AL1702
3.3VGA & DDC interface (Circuit diagrams MAIN PWB 4 of 8)
The analog video signals input, the AC-coupled video signal video signal is used to clamp the black level at
0V. and H/V sync to sclaer, and DDC plug & play function.
3.3.1P302 connector
The video input signals from the P302 connector.
3.3.2I304 DDC EEPROM
This IC is support DDC2B of the VESA standard, also plug and play for the PC host.
3.4Scaler MST8111B (Circuit diagrams MAIN PWB 5 of 8)
The I305 is scaled converter LSI for the LCD monitor.
The analog R, G, B signal input entered from the video input circuit is converted into the digital data of video
signal through the incorporated A/D converter. Based on this conversion, this device performs interpolation
during pixel extension. These interpolation digital data are transformed to LVDS signal. The I305 source
voltage is 3.3V and 2.5V, the device clock frequency is 14.318 MHz. The device control signal is from MCU
through the 3-wire bus.
The I305 scaler has support OSD function.
3.5Panel interface (Circuit diagrams MAIN PWB 6 of 8)
3.5.1P305 connector
The P305 is LVDS bus, output to LCD module. The output voltage is 5 voltage.
3.5.2MCU (Circuit diagrams MAIN PWB 7 of 8)
The I307 MCU is system processor. It can programmed scaler, control power save sequence for the
system, input keypad function, output LED, control audio function, and ISP / DDC2Bi function.
Page 5
3.5.3X302 crystal
The X302 crystal is 11.0592MHz, support the operated clock to the MCU.
3.5.4Reset circuit
The C396, R379, D316 is support reset signal to the MCU, then MCU have output hardware reset signal
(HWRESET) to the scaler.
3.5.5I308 EEPROM
The I308 is 24LC16 EEPROM, the data transfer between I308 and MCU is effected through the IIC bus
SCL (pin14) and SDA (pin13) of MCU. The OSD related setting data, I305 control data and other service
data, to be stored in I308.
3.5.6P308 connector
The P308 has support keypad function. Control is give effect to for the push switch to be used when
the user changes the parameters, in order to modify the respective setting values. Whether the switch
has been pressed is identified with the switch input level that is turned “L”.
Each switch input port is pulled up at outside of MCU. Related ports of I307 based on Table 1.
Each parameter is stored in the I308 EEPROM, the contents of which are updated as required.
The P308 have LED Green and Amber light, the LED Green signal pin 36 from I307 MCU, and the LED
Amber signal pin 37 from I307 MCU.
AL1702
Table 1 Related ports of I307
Pin No. I/O Signal name Function Remarks
Pin 3 I KEY_POWER Soft power switch input Power key
Pin 2 I KEY_MENU Exit/Enter switch input Enter / withdraw from
OSD
Pin 41 I KEY_DOWN
Pin 42 I KEY_MINUS
Pin 1 I KEY_PLUS
↓ switch input
← switch input
→ switch input
Down key
- / Mute key
+ / Auto key
3.5.7Audio control function
The I307 MCU output signal control audio mute and power, the pin33 is mute signal, the pin32 is
controlled audio power signal.
3.5.8Scaler programmed function
The I307 MCU is used DDR direct bus, between I305 MST8111B and MCU I307.
3.5.9ISP and DDC2Bi function
The DDC2Bi is VESA standard for the host PC system, it can through DDC2Bi bus control LCD monitor.
The I309 will off DDC_CLK and DDC_DAT signal, when LCD monitor is no power.
Can use ISP function for firmware modification.
The pin29 is bus clock (DDC_CLK), the pin28 is bus data (DDC_DAT). It is same of the IIC data bus.
3.5.10The power save sequence function
First disable I307 pin31 (BKLT_EN) from H to L of LCD module back light power, delay some time, then
disable I307 pin9 (PANELVCC_EN) from H to L of LCD module power, and disable I307 pin32
(AUDIO_EN) from H to L of audio power, and through 3-wire bus programmed I305 MST8111B to
power down mode.
Page 6
3.6Audio (Circuit diagrams MAIN PWB 8 of 8) [OPTION]
3.6.1P309 connector
The audio signal input received from the audio input terminal P309 from the jack input of the jack
board, P309 is applied to amplifier I311 of pin4 (L-CH) and pin9 (R-CH) through the low-pass filter
consisting of R417, R418, C419 and C420.
3.6.2P310 connector
The audio signal is output to the audio output terminal P310, and to the internal speaker system.
3.6.3I310 MOSFET
I310 MOSFET (CEM9435A) is cut audio power (12V) for the power save sequence. The signal
(AUDIO_EN) is ON/OFF I310 MOSFET through the Q311 control.
3.6.4I311 amplifier
The I311 TDA7496L is audio amplifier, I311 operated power voltage is 12V.
I311 pin4 and pin9 is audio input port.
I311 pin14 and pin17 is audio output port.
I311 pin 12 is mute input from I307 MCU. The pin 6 is audio volume from the I305 MST8111B.
4Others
4.1Detection of POWER switch status
The MCU identifies the ON status of the two power supplies. The identification is made when the
power supply is turn off. For example, if the power supply is turn off with the POWER switch, the
POWER switch must be turn on when active the power supply again. If the power supply is turned off
by pulling out the power cord, then this power supply can be turned on by connecting the power cord,
without pressing the POWER switch.
4.2Display mode identification
4.2.1Display mode identification
The display mode of input signal is identified based on Table 2.
When the mode has been identified through the measurement of horizontal and vertical frequencies,
the total number of lines is determined with a formula of “Horizontal frequency / Vertical frequency =
Total number of number of lines”. Final identification can be made by examining the coincidence of the
obtained figure with the number of lines for the mode identified from the frequency. The Distinction
Hsync and Vsync of each mode is shown in Table 3.
When the detected frequency if the sync signal has changed, the total number of lines should be
counted even through it is range identified frequency in the same mode.
4.2.2Out of range
This out of range mode is assumed when the frequency out of the horizontal / vertical signal is as
specified below.
Vertical frequency : 56 ~ 76 Hz.
Horizontal frequency : 30 ~ 81.1KHz.
4.2.3Power save mode
The power save mode is assumed when the horizontal / vertical signals are as specified below.
If there is no horizontal sync signal input.
If there is no vertical sync signal input.
If the horizontal sync signal is outside the measuring range of MST8111B.
AL1702
If the vertical sync signal is outside the measuring range of MST8111B.
Page 7
Table 2 video mode
AL1702
Resolution H-Freq
(KHz)
Band Width
(MHz)
Polarity Mode
H V
1 720x400 (70Hz) 31.469 28.322 - +
2 640x480 (59.94Hz) 31.469 25.175 - 3 640x480 (66.67Hz) 35 30.24 - 4 640x480 (72Hz) 37.861 31.5 - 5 640x480 (75Hz) 37.5 31.5 - 6 800x600 (56.25Hz) 35.156 36 + +
7 800x600 (60Hz) 37.879 40 + +
8 800x600 (72Hz) 48.077 50 + +
9 800x600 (75Hz) 46.875 49.5 + +
10 832x624 (74.55Hz) 49.722 57.28 - 11 1024x768 (60Hz) 48.363 65 - 12 1024x768 (70Hz) 56.476 75 - 13 1024x768 (75Hz) 60.023 78.75 + +
14 1152x864 (75Hz) 67.5 108 + +
15 1280x960 (60Hz) 60 108 + +
16 1280x1024 (60Hz) 63.981 108 + +
17 1280x1024 (75Hz) 79.976 135 + +
Table 3 the Hsync, Vsync distinction
Indication
Distinction Hsync Distinction Vsync The fixed
resolution
720 x 400
640 x 480
800 x 600
832 x 624
1024 x 768
1152 x 864
1280 x 960
1280 x 1024
1280 x 1024
30.5KHz≦fH≦32.5KHz 69Hz≦fV≦71Hz
30.5KHz≦fH≦32.5KHz 59Hz≦fV≦61Hz
34KHz≦fH≦36KHz 65.7Hz≦fV≦67.7Hz
36.9KHz≦fH≦38.9KHz 71.8Hz≦fV≦73.8Hz
36.5KHz≦fH≦38.5KHz 74Hz≦fV≦76Hz
34.2KHz≦fH≦36.2KHz 55.3Hz≦fV≦57.3Hz
36.9KHz≦fH≦38.9KHz 59.3Hz≦fV≦61.3Hz
47.1KHz≦fH≦49.1KHz 71.2Hz≦fV≦73.2Hz
45.9KHz≦fH≦47.9KHz 74Hz≦fV≦76Hz
48.7KHz≦fH≦50.7KHz 73.5Hz≦fV≦75.5Hz
47.4KHz≦fH≦49.4KHz 59Hz≦fV≦61Hz
55.5KHz≦fH≦57.5KHz 69Hz≦fV≦71Hz
59KHz≦fH≦61KHz 74Hz≦fV≦76Hz
66.5KHz≦fH≦68.5KHz 74Hz≦fV≦76Hz
59KHz≦fH≦61KHz 59Hz≦fV≦61Hz
62.9KHz≦fH≦64.9KHz 59Hz≦fV≦61Hz
79KHz≦fH≦81KHz 74Hz≦fV≦76Hz
mode
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Page 8
4.3Power ON sequence
When the POWER switch is pressed, the POWER OFF signal is turned “H”. when this “H” potential is
detected, the CPU begins to establish the respective power supplies according to the sequence show below.
AL1702
Power Switch
157 ms
LED_G (LED)
1.8 sec
PANELVCC_EN
(Panel VCC)
1.84 sec
PCLK/DATA
(LVDS bus)
2 sec
BKLT_EN
(Backlight Power)
2 sec
AUDIO_EN
(Audio VCC)
4.4Power OFF sequence
When the POWER switch is pressed, while the power supply is ON, the POWER ON signal is turned “H”.
when this “H” potential is detected, the CPU begins to turn off the respective power supplies according to
sequence show below.
Power Switch
LED_G
(LED)
PANELVCC_EN
(Panel VCC)
PCLK/DATA
(LVDS bus)
BKLT_EN
(Backlight Power)
AUDIO_EN
(Audio VCC)
90 ms
350 ms
316ms
90 ms
1.55 sec
Page 9
4.5List of I/O Pin Assignments of the I307
Pin No. Port Signal Name Initial
3 P5.0 KEY_POWER H ON/OFF monitor power
2 P5.1 KEY_MENU H OSD enter/exit enable
1 P5.2 KEY_PLUS H OSD right enable
42 P5.3 KEY_MINUS H OSD left enable
41 P5.4 KEY_DOWN H OSD down enable
38 P1.0 LED_G H LED green enable
37 P1.1 LED_A H LED amber enable
20 P1.2 SCL H Clock of 3-wire bus for scaler
21 P1.3 SDA H Data of 3-wire bus for scaler
22 P1.4 CSZ H Chip select of 3-wire bus for scaler
25 P1.5 HWRESET H Reset enable to scaler
29 P3.0 RXD H UART interface data IN
28 P3.1 TXD H UART interface data OUT
19 P3.2 INT H Interrupt signal from the scaler
13 P3.4 ISDA H EEPROM data bus
14 P3.5 ISCL H EEPROM clock bus
27 P6.0 DDC_WP L DDC EEPROM write protection
26 P6.1 VGA_DET H VGA cable connected
9 P6.3 PANELVCC_EN L Panel power enable
31 P6.5 BKLT_EN L Back light power enable
32 P6.6 AUDIO_EN L Audio power enable
33 P6.7 MUTE L Audio mute enable
Note : Other I/O pin assignments of the I305 MST8111B
73 PWM0 BKLT_ADJ - Backlight brightness control
74 PWM1 VOLUME - Audio volume control
AL1702
Function
Setting
Page 10
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