Iiyama AS3921U User manual

Contents
SERVICE MANUAL
AS3921U
1. REPLACING THE BACKLIGHT
2. SET-UP ADJUSTMENTS
3. CIRCUIT DESCRIPTION
4. SERVICE PARTS LIST
5. EXPLODED VIEW
6. DIAGRAMS

SERVICE MANUAL October 27, 2000
Revision
NO. S1500E04
710-1 Kitaowaribe, Nagano-shi 3 1-0014 JAPAN
Iiyama Corporation
Copyright
AS3921U

[ Revision Record ]
Rev. Section Contents

CONTENTS
NOTICE
The information in this document is subject to change without notice.
- Page-
SAFETY PRECAUTION ................................................................................... i - ii
1. REPLACING THE BACKLIGHT .................................................................... 1
2. SET-UP ADJUSTMENTS.............................................................................. 2 - 5
3. CIRCUIT DESCRIPTION ............................................................................... 6 - 9
4. SERVICE PARTS LIST ................................................................................ 10 - 25
5. EXPLODED VIEW ....................................................................................... 26 - 3
6. DIAGRAMS ................................................................................................. 39 - 44

Many electrical and mechanical parts in the products have special safety-related characteristics. These
characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily
be obtained by using replacement components rated for higher voltage, wattage, etc. Replacement parts which
have these special safety characteristics are identified in the parts list of Service manual. Electrical components
having such features are identified by mark on the schematics and “!” on the parts list in Service manual. The
use of a substitute replacement which does not have the same safety characteristics as the recommended
replacement part shown in the parts list of Service manual may create shock, fire, or other hazards.
 SAFETY PRECAUTION 
1. The design of this product contains special hardware, many circuits and components specially for safety purposes.
For continued protection, no changes should be made to the original design unless authorized in writing by the
manufacturer. Replacement parts must be identical to those used in the original circuits. Service should be
performed by qualified personnel only.
i
Alterations of the design or circuitry of the products should not be made. Any design alterations or additions will
void the manufacturer's warranty and will further relieve the manufacturer of responsibility for personal injury or
property damage resulting therefrom.
2.
3.
Use isolation transformer.
The chassis and any sub-chassis contained in some products are connected to the primary circuit of the AC
power line. An isolation transformer of adequate capacity should be inserted between the product and the AC
power supply point while performing any service on some products when the primary circuit of the AC power
supply is exposed.
4.
Isolation Check
(Safety for Electrical Shock Hazard)
After reassembling the product always perform an isolation check on the exposed metal parts of the cabinet
(video input and output terminals, control knobs, screwheads, control shafts, etc.) to be sure the product is safe
to operate without danger of electrical shock.
5.
Dielectric Strength Test
The isolation between the AC primary circuit and all metal parts exposed to the user, particularly any exposed
metal part having a return path to the chassis should withstand a voltage of 1,500V AC(r.m.s.), 20mA(current
sensitivity) for a period of one minute.
This method of test requires a test equipment not generally found in the service trade.
(1
Leakage Current Check
Plug the AC line cord directly into the AC outlet (do not use a line isolation transformer during this check.). Using
a “Leakage Current Tester”, measure the leakage current from each exposed metal part of the cabinet, particularly
any exposed metal part having a return path to the chassis, to a known good earth ground (water pipe etc.). Any
leakage current must not exceed 3.5mA AC(r.m.s.).
(2
!

Alternate Check Method
Plug the AC line cord directly into the AC outlet (do not use a line isolation transformer during this check.). Use an
AC voltmeter having 1,000 ohms per volt or more sensitivity in the following manner. Connect a 1,500Ω 10W resistor
paralleled by a 0.15uF AC-type capacitor between an exposed metal part and a known good earth ground (water
pipe etc.).
Measure the AC voltage across the resistor with the AC voltmeter. Move the resistor connection to each exposed
metal part, particularly any exposed metal part having a return path to the chassis, and measure the AC voltage
across the resistor. Now, reverse the plug in the AC outlet and repeat each measurement. Any voltage measured
must not exceed 2.45V AC(r.m.s.). This corresponds to 3.5mA AC(r.m.s.).
GOOD EARTH GROUND
PLACE THIS PROBE ON
EACH EXPOSED METAL
PART
AC VOLTMETER
(HAVING 1,000Ω/V OR MORE SENSITIVITY)
0.15uF AC-TYPE
1,500Ω 10W
ii

1. REPLACING THE BACKLIGHT
- 1 -
Note: Replacing the Backlight should be performed by qualified personnel only.
<Replacement procedure>
1. Separate the LCD module from the
chassis. (See Figure 1)
Refer to ASSY-LCD in 5. EXPLODED
VIEW for taking LCD panel apart.
2. Pull down A Stopper toward A with –
screwdriver or the like.
(See Figure 2)
3. Pull out B Backlight toward B.
4. Insert a new Backlight.
Note: The both top and bottom
Backlights should be replaced at the
same time.
5. Re-assemble in reverse order.
Figure 1
Figure 2
B
AA
B
LCD module

- 2 -
2. SET-UP ADJUSTMENTS
The following adjustments should be made when a complete realignment is required or a new PWB is installed.
<Required measuring equipment>
Signal generator (Programmable video generator)............. Leader 1610A
Headphones
CD player
Audio-LR confirmation equipment
USB compliant computer
Short-connector for LCD (Iiyama handmade)
B
0.51
4.44
C
0.51
2.22
<Preparation>
Connect the signal cable from the signal generator to the monitor.
Adjustment data is automatically saved in the memory when the on screen display disappears.
1.
2.
Note: This monitor should be checked and adjusted by connecting it to a signal generator, then entering
and running the timing charts below.
R
1 .113
17.779
Q
0.000
0.259
O
1 .150
1 .150
D
34.75
29.63
S
0.000
0.001
P
0.037
0.111
E
1.27
0.75
Vertical (msec)
Horizontal (µsec)
A
37.04
37.04
V
N
P
Sync polarity
H
N
P
Resolution
1032×4 9
640×4 0
Comp
–
–
Sync
on
green
–
–
fH
(kHz)
27.000
27.000
ADJUSTMENT MODE
There are two different modes available to adjust the monitor as described below. The adjustments with ‘G’ in front
of the title are only available under Factory Mode. You can perform the other adjustments by either User or Factory
Mode. Please change the mode as required.
USER MODE:
Turn ON the Power Switch and you are in the User Mode.
FACTORY MODE:
Turn OFF the Power Switch and short between pins 1 and 4 of Connector F on the PWB-MAIN with a short-
connector. Turn ON the Power Switch and you are in the Factory Mode. Turn OFF the Power Switch and remove
the short-connector from Connector F to exit.

- 3 -
2-1. Automatic RGB GA N and B AS adjustment
1) Receive an entire black raster signal of fH 27.000 kHz. (H/V sync polarity: N)
2) Confirm the Power Indicator turns to orange.
3) Confirm that the Power Indicator turns to green when the adjustment is completed.
4) Receive an entire white raster signal of fH 27.000 kHz. (H/V sync polarity: P)
5) Confirm the Power Indicator turns to orange.
6) Confirm that the Power Indicator turns to green when the adjustment is completed.
6) Turn OFF the Power Switch and turn it ON again under the User Mode.
6) Select Reset and press the Menu Button, and select Yes and press the Menu Button.
G
PROCEDURE
1. To make the lock out facility available
1) Turn ON the Power Switch while pressing the Menu Button, and then turn OFF the Power Switch.
2) Turn ON the Power Switch again while pressing the + Button, and then turn OFF the Power Switch.
3) Turn ON the Power Switch again while pressing the - Button.
2. To cancel the lock out facility
1) Turn OFF the Power Switch.
2) Turn ON the Power Switch while pressing the Menu, - and + Buttons at the same time so that the lock
out facility is canceled.
LOCK OUT FACILITY
User adjustable items can be restricted to OSD Position and Language by setting the lock out facility.

1) Connect cables according to the user manual.
2) Turn ON the Power Switch of the monitor and computer.
3) Double-click “Universal serial bus controller” as shown in Fig 1 on next page.
4) Confirm that “Generic USB Hub” or “Iiyama USB Hub” appears as shown in Fig 2.
5) Disconnect the USB Cable from the USB compliant computer.
6) Double-click “Universal serial bus controller”.
7) Confirm that “Generic USB Hub” or “Iiyama USB Hub” disappears as shown in Fig 3.
) Connect the USB Cable to the stand.
9) Repeat 1) to 5) and confirm that the USB function works normally.
2-3. USB Operation Check
- 4 -
2-2. AUD O confirmation [PWB-AUD O]
1) Turn the Volume Control from minimum to maximum and make sure the sound is normal without hum
etc.
2) Set the Volume Control at mechanical center.
3) Connect the output of a CD player to the Audio Connector and make sure the right and left speaker
works normally.
4) Turn the Volume Control and make sure the volume varies.
5) Connect Audio-LR confirmation equipment between the Audio Connector and CD player.
6) Turn off left switch of the Audio-LR confirmation equipment and make sure the right speaker works
normally.
7) Turn off right switch of the Audio-LR confirmation equipment and make sure the left speaker works
normally.
) Turn the Volume Control to minimum and connect headphones to the Headphone Connector.
9) Confirm that the Headphones don't make noise.
10) Turn the Volume Control from minimum to maximum and make sure the sound from the both headphones
is well balanced and normal without hum etc.

- 5 -
Fig. 2 Fig. 3
Fig. 1
Double-click
here
“Generic USB Hub” or “Iiyama USB Hub”

3. CIRCUIT DESCRIPTION
3-1. POWER circuit
The Power source of AC90-264V is converted to DC12V, DC 5V (USB) and DC14V by the POWER-UNIT. Converted
DC12V is supplied to PWB-MAIN, inverter and the backlight as a power source. DC12V and DC14V supplied to
PWB-MAIN is regulated to power source of each block by the regulator IC. The Power sources except IC902 are
controlled by the MICROPROCESSOR (IC701).
A12V line: Supplied to the inverter and backlight as power source.
B5V line: Supplied to the MICROPROCESSOR (IC701), VIDEO SW (IC101) and around as power source.
This power source is always turned on.
C3.3V line: Supplied to the logic circuit of the MEMORY IC and TFT CONTROLLER as power source.
This power source is controlled by LOG_POW signal from the MICROPROCESSOR (IC701).
D3.3V line: Supplied to the LVDS TRANSMITTERS as power source. This power source is controlled by
LOG_POW signal from the MICROPROCESSOR (IC701).
E3.3V line: Supplied to the DC-AC CONVERTER and PLL as power source. This power source is
controlled by PLL_EN signal.
F12V line: Supplied to the PANEL MODULE as power source. This power source is controlled by
LCD_POW signal.
The Power source of C, D, E and F are turned off by the MICROPROCESSOR (IC701) when the system is
stand-by mode (Power indicator turns orange).
- 6 -
POWER-UNIT
POWER SW
A
12V
Backlight Power
5V USB Power
LOG POW
LCD-POW
PLL_EN
PWB-MAIN
PWB-AUDIO
12V IC903
B
5V
C
3.3V
E
3.3V
D
3.3V
IC902
F
12V
Panel Power
IC701
MICROPROCESSOR
Audio jack
AUDIO
ON/OFF
6.5V Audio Power
IC301
AC
90-264V
Q904
IC905
IC906

3-3. ON SCREEN D SPLAY CONTROL circuits
H/V Sync signals from IC501 are converted to 3.3V - 5V by the LEVEL CONVERTER (IC704). The output is then
passed to the OSD CONTROLLER (IC301). IC301 is controlled by I2C-BUS from the MICROPROCESSOR (IC701).
OSD signals (R, G, B, BLK) generated by IC301 are applied to IC501 directly and combined with the video signal by
IC501.
- 7 -
3-2. SYNC PROCESS NG circuit
H/V Sync signal from the PWB-A/V is passed to the SYNC PROCESSING IC (IC204) via Schmitt input BUFFER
(IC202). Sync On Green is separated into VIDEO signal and Sync signal by IC203. The output of IC203 is passed
via the BUFFER (IC202) to IC204. When only one of the two signal inputs is connected to the signal source, the
one connected is automatically selected by IC204. When both of the signal inputs are connected to the signal
source, the separate sync signal is selected by IC204. IC204 maintains polarity uniformly, separates H/V Sync
signal and generates the clamp pulse. IC204 transmits information of the input sync signal presence and polarity
to the MICROPROCESSOR (IC701). H Sync signal is positive polarity and input to IC401. V Sync signal is positive
polarity and input to IC501.
Note*: V Sync signal on CS signal and Sync On Green signal should have the same period H Sync signal
between its two adjacent rising edges throughout a rame.
Green
H/CS
V
V
CS V
H
POL
ST
X'TAL
X201
CLAMP
5Vp-p
H/CS
BUFFER
IC202
VIDEO SYNC
SEPARATER
MICROPROCESSOR
IC701
TFT
CONTROLLER
IC501
A/D, PLL
IC401
SYNC
PROCESSSING
IC204
IC203
H
V Sync
Note*
OSD
CONTROLLER
IC301
LEVEL
CONVERTER
IC704 TFT
CONTROLLER
IC501
CLK,DAT
R,G,B,BLK
H,V,CLK
CLK
H,V
I
2
CBUS
MICROPROCESSOR
IC701

3-4. FREQUENCY CONVERS ON circuit
The input signals from DC-AC CONVERTER (IC401) to TFT CONTROLLER (IC501) are memorized in the MEMORY
(IC502 and IC503). The input signals are converted to SXGA at 60Hz when read out from the MEMORY.
- -
The same frequency as the input signal
TFT CONTROLLER
IC501
R,G,B, DATA
R,G,B, DATA
R,G,B, DATA
SXGA@60Hz
R,G,B, H, V, DE
SXGA@60Hz
MEMORY
IC502
IC503
IC601
IC602
A/D
CONVERTER
IC401
3-5. PANEL DR VE circuit
R, G, B video signals are each passed to the LVDS TRANSMITTER (IC601 and IC602) as a 4 bit (R,G,B bit / 2ch)
digital data with H, V, DE, CLK after gamma-correction and OSD mixing. This digital data is always maintained at
SXGA size by setting the coefficient of expansion to IC501 when the MICROPROCESSOR (IC701) discriminates
the input signal other than SXGA. IC601 and IC602 converts the input signal parallel to serial according to the LVDS
procedure, and output to the PANEL MODULE.
RA0-RA7 RB0-RB7
GA0-GA7 GB0-GB7
BA0-BA7 BB0-BB7
48bit
ST
CLK
DAT
TFT PANEL
CONTROLLER
IC501
LVDS
TRANSMITTER
IC601
IC602
LVDS
RECEIVER
MFB
PWB-MAIN
PANEL MODULE
DE,CLK
LVDS-EN
12V
PANEL
POWER
MICROPROCESSOR
IC701

3-6. BACKL GHT and NVERTER (BR GHTNESS) CONTROL circuit
The inverter converts DC12V to the power source of AC650Vrms for lighting the backlight by the DC-AC CONVERTER,
and turns on the cold cathode tube.
Signals controlled by the MICROPROCESSOR (IC701) are as follows:
BKLTC signal: Turn ON and OFF the inverter output and applied for picture mute.
BRT signal: Applied for Brightness and controlled by the DC voltage.
- 9 -
IC701
PWB-MAIN
12V Backlight Power
INVERTER
BKLTC
CFL
BRT
BKLTC, BRT
ON /
OFF
Controller OUT
AC650Vrms

- 10 -
4. SERVICE PARTS LIST
WARNING !
The components identified by “ ! ” in this manual are critical
for safety.
Replace only with part number specified.
<C NTENTS>
 Structure 
ASSY-PACKING
ASSY-LCD
FAMILY-TREE
ASSY-PWB-MAIN
ASSY-PWB-MIX2
ASSY-STAND
ASSY-PWB-USB
SUB-MATERIAL
- Page-
Abbreviations and Marks .................................................................................. 11
FAMILY-TREE .................................................................................................. 12
ASSY-PACKING .............................................................................................. 12
ASSY-LCD ....................................................................................................... 13
ASSY-PWB-MAIN ........................................................................................... 14-21
ASSY-PWB-MIX2............................................................................................. 22-23
ASSY-STAND .................................................................................................. 23
ASSY-PWB-USB ............................................................................................. 24
SUB-MATERIAL ............................................................................................... 25

- 11 -
Abbreviation Meaning
R-C
R-MB
C-C
C-E
C-E-NP
C-MF
D
ZD
TR
VR
SW
Resistor-Carbon
Resistor-Metal
Capacitor-Ceramic
Capacitor-Electrolytic
Capacitor-Electrolytic Non-Polar
Capacitor-Stacked Metallized Plastic Film
Diode
Zener Diode
Transistor
Variable Resistor
Switch
 Marks in DESCRIPTI N section 
ELECTRICAL PARTS LIST
 Abbreviations in PART section 
<Resistor> <Capacitor>
Mark
F
J
Tolerance
± 1%
± 5%
Mark
J
K
M
Z
Tolerance
± 5%
± 10%
± 20%
+ 80%
– 20%

5. EXPLODED VIEW
- 26 -
Note: The numbers in this exploded view are the same as the reference numbers in the Chapter 4.
54
ASSY-LCD
33
14
34
26
30
L=100mm×2

- 27 -
(4)
5-6
15-20
10-20
LNN
HNB
HNE
LNJ
FRONT
Windows 95/98/2000Plug&Play
USB Hub
JAPAN
GOLF TOUR
48
45
44
22
31
46
394041
29
57
52
L=30mm
×2
36
L=600mm
51
L=600mm
53
37
18

- 28 -
Note: Except where indicate otherwise, all screw torcue
is 8±1kgf-cm in ASSY-LCD.
15
7
50±5
FRAME-MAIN
INVERTER-CARD
A
G
J
J
J
L=15
89
38
13
UL-TAPE
89
L=50 ×5
×2
67
×4
79
85
78
39
51
×4
47
52 ×3
47
ASSY-1