Dell S2421H Instructions for use

Product Announcement:
This product is certificated to meet RoHS
Directive and Lead-Free produced definition.
Using approved critical components only is
recommended when the situation to replace
defective parts. Vender assumes no liability
express or implied, arising out of any unauthorized
modification of design or replacing non-RoHS
parts. Service providers assume all liability.
Qualified Repairability:
Proper service and repair is important to the safe,
reliable operation of all series products. The
service providers recommended by vender should
be aware of notices listed in this service manual in
order to minimize the risk of personal injury when
perform service procedures. Furthermore, the
possible existed improper repairing method may
damage equipment or products. It is recommended
that service engineers should have repairing
knowledge, experience, as well as appropriate
product training per new model before performing
the service procedures.
NOTICE:
! To avoid electrical shocks, the products should be
connected to an authorized power cord, and turn
off the master power switch each time before
removing the AC power cord.
! To prevent the product away from water or
expose in extremely high humility environment.
! To ensure the continued reliability of this
product, use only original manufacturer’s
specified parts.
! To ensure following safety repairing behavior, put
the replaced part on the components side of
PWBA, not solder side.
! To ensure using a proper screwdriver, follow the
torque and force listed in assembly and
disassembly procedures to unscrew screws.
! Using Lead-Free solder to well mounted the
parts.
! The fusion point of Lead-Free solder requested in
the degree of 220°C.
1. Important Safety Notice

2. Exploded view diagram with list of items

3. Wiring Connectivity Diagram
Panle 1920*1080
Power Board
HDMI HDMI Line Out
FK BD
KB1 speaker
Interface Board

4. Disassembly and Assembly Procedures
S2
4.1 Disassembly Procedures:
S1
S3
Remove the monitor stand base:
1. Place the monitor on a soft cloth or cushion.
2. Press the stand down to access to the release latch.
3. Use a long screwdriver to press the release latch.
While pressing the release latch, slide out the
stand assembly from the monitor.
Use one hand to press the rear cover, then wedge
your fingers between the rear cover and the middle
bezel on the corners of the top left side to the right
side of the monitor to release the rear cover.
To remove the VESA cover: Press the dimple on the
VESA cover to release it from the back of the display.
Use a Philips-head screwdriver to remove 6pcs
screws for unlocking mechanisms.
(No.1~4 screw size=M4x11; Torque=7 8kgfxcm;
No.5~6 screw size=M4x8; Torque=7 8kgfxcm)
~
~
S4
1
3
22
23
41
5
6
Tear off 2pcs acetate tapes and then disconnect the
speaker cable away from the connector. Use a
Philips-head screwdriver to remove 6pcs screws for
unlocking the speakers with middle bezel.
(No.1~6 screw size=M3x8, Torque=5~6kgfxcm)
S5
Tear off 1pcs aluminum foil and then remove the two
speakers. Disconnect the panel lamp cable away
from the connector of the panel module.
S6
1
5
4
6
2
3
Necessary repair and test equipment:
1. Philips-head screwdriver

4. Disassembly and Assembly Procedures
Tear off 1pcs aluminium foil, and then disconnect the
function key cable away from the connector.
S8
Take away the middle bezel. U
tear off the tapes for releasing the key cables.
se a Philips-head
screwdriver to remove 3pcs screws for unlocking the
function key board with the middle bezel, and then
(No.1~3 screw size=M2x2.4, Torque=0.8±0.2kgfxcm
S10
Tear off the tape, then lift up the panel module with
the bracket chassis for releasing the front bezel
away from the panel module.
Use a Philips-head screwdriver to remove 2pcs
screws for unlocking the bracket with middle bezel,
to remove 2pcs screws for unlocking the bracket
with the panel module.
(No.1~2 screw size=M3x4, Torque=3~4kgfxcm;
No.3~4 screw size=M3x3.5, Torque=2~3kgfxcm )
21
43
S9
31
2
Use a Philips-head screwdriver to remove 16pcs
screws for unlocking the middle bezel.
(No.1~11 screw size=M3x4, Torque=3~4kgfxcm;
No.12~16 screw size=M2x3.3, Torque=1±0.2kgfxcm)
2
13
12
1
15
3
8
6
11
9
7
45
10
16
14
S7
S11
Take away the bracket chassis module and then put
the bracket chassis module on a protective cushion.
S13
Unplug the LVDS cable from the connector of the
panel module by pushing the earing-locks.
S12

4. Disassembly and Assembly Procedures
Remove the interface board and power board from
the bracket chassis module carefully, and disconnect
all the cables.
Use a Philips-head screwdriver to remove six screws
for unlocking the circuit board, release all the cables
from the hooks.
(No.1~5 screw size=M3x7.5, Torque=6±0.5kgfxcm;
No. 6 screw size=M4x8, Torque=6±0.5kgfxcm)
S15
S16
Remove the Mylar from the hooks of the bracket
chassis module.
S14
34
6
25
1

4. Disassembly and Assembly Procedures
Take a mylar to insert the hooks of the bracket to
cover the power board.
S5
Panel preparation: Take out 1pcs panel module from
the carton, then remove the protective film by tearing
off the tapes, and then examine the panel surface
according to inspection criteria. Turn over the panel,
and then place screen faced down for later
assembling.
S7
S6
Turn over a power board and put the power board
into the bracket chassis, locate the panel power
cable into the hook of the bracket chassis.
Place a bracket chassis base on a protective
cushion.
4.2 Assembly Procedures:
S2
S1
Take a interface board, connect a LVDS cable to the
connector of the interface board, then connect the
cable of the power board to the connector of the
interface board. Turn over the interface board and
locate it into the bracket. Use a Philips-head
screwdriver to tighten six screws for locking the
power board and interface board.
(No.1~5 screw size=M3x7.5, Torque=6±0.5kgfxcm;
No.6 screw size=M4x8, Torque=6±0.5kgfxcm)
34
S3
6
25
Move the bracket chassis close to the panel, then
connect LVDS cable to the connector of the panel
module. Turn over the bracket and put it on the back
of panel module.
1

4. Disassembly and Assembly Procedures
Use a Philips-head screwdriver to tighten 2pcs
screws for locking the bracket with middle bezel, to
tighten 2pcs screws for locking the bracket with panel.
(No.1~2 screw size=M3x4, Torque=3~4kgfxcm;
No.3~4 screw size=M3x3.5, Torque=2~3kgfxcm )
Connect the panel lamp cable to the connector of
panel module.
Take a function key board and a middle bezel, then
fix the middle bezel with a fixture, and locate the
function keyboard into the hooks of the bezel Use a
Philips-head screwdriver to tighten 3pcs screws for
locking the function key board with the middle bezel.
.
(No.1~3 screw size=M2x2.4, Torque=0.8±0.2kgfxcm
S13
Move the middle bezel with function key board close
to the panel unit, tear off the papers of the tapes on
the back of the key cable, and then fix the key cable
on the bezel by 3pcs tapes, then assemble the
middle bezel with the front bezel and panel module.
S14
31
2
Connect the function key cable to the connector of
board, then paste 1pcs aluminum foil to cover the
LVDS connector and key cable.
S11
S12
S10
S9
Paste 1pcs tape to cover the LVDS connector. Take
1pcs front bezel, then lift up the panel with bracket
and assemble the front bezel with the panel module.
S8
21
43
Use a Philips-head screwdriver to lock 11pcs screws
for locking the middle bezel with the panel module,
then lock 5pcs screws for locking the middle bezel
with front bezel.
(No.1~11 screw size=M3x4, Torque=3~4kgfxcm;
No.12~16 screw size=M2x3.3, Torque=1±0.2kgfxcm)
2
13
12
1
15
3
8
6
11
9
7
45
10
16
14

4. Disassembly and Assembly Procedures
Use a Philips-head screwdriver to tighten 4pcs
screws for locking rear cover with the assembled
unit, to tighten 2pcs screws for locking the rear
cover with bracket chassis module.
(No.1~4 screw size=M4x11; Torque=7 8kgfxcm;
No.5~6 screw size=M4x8; Torque=7 8kgfxcm)
~
~
Take 1pcs rear cover, put down the rear cover
and push the rear cover on the positions marked
as the picture below shown for mechanisms
engagement.
S17
Take a pair of speakers to locate the probers of the
middle bezel, then connect the speaker cable to the
connector of the board. Paste 1pcs aluminum foil to
fix the bracket on the specific position.
S15
S18
Use a Philips-head screwdriver to tighten 6pcs
screws for locking the speakers with middle bezel.
Settle the cable and then fix the speaker’s cables
with 2pcs acetate tapes on the specific position as
the picture below shown.
(No.1~6 screw size=M3x8, Torque=5~6kgfxcm)
S16
23
41
L
front bezel with panel module , then provide power
supply and a video signal to the monitor, then turn
on the monitor for functionality check.
ift up the monitor to checking the gap between the
S20
Stick 2pcs labels on the specific positions as the
picture below shown. Take 1pcs stand riser and
1pcs stand base, assemble the stand base with
stand riser, then rotate the screw clockwise to lock
the stand base and stand riser. Insert the stand-riser
into monitor groove until it snaps into its place.
S19
1
5
4
6
2
3
5
6

5. Trouble Shooting Instructions
Self-test
Your monitor provides a self-test feature that allows you to check whether your
monitor is functioning properly. If your monitor and computer are properly connected
but the monitor screen remains dark, run the monitor self-test by performing the
following steps:
1. Turn o both your computer and the monitor.
2. Unplug the video cable from the back of the computer. To ensure proper Self-Test
operation, remove all video cables from the back of computer.
3. Turn on the monitor.
The floating dialog box should appear on-screen (against a black background), if the
monitor cannot sense a video signal and is working correctly. While in self-test mode,
the power LED remains white. Also, depending upon the selected input, one of the
dialogs shown below will continuously scroll through the screen.
The display will go into Standby mode in 4 minutes.
www.dell.com/S2421H
www.dell.com/S2721H
Dell 24/27 Monitor
S2421H/S2721H
No HDMI1 Cable
or
The display will go into Standby mode in 4 minutes.
www.dell.com/S2421H
www.dell.com/S2721H
Dell 24/27 Monitor
S2421H/S2721H
No HDMI2 Cable
4. This box also appears during normal system operation if the video cable is
disconnected or damaged.
5. Turn o your monitor and reconnect the video cable; then turn on both your
computer and the monitor.
If your monitor screen remains blank after you use the previous procedure, check your
video controller and computer, because your monitor is functioning properly.

5. Trouble Shooting Instructions
Built-in diagnostics
Your monitor has a built-in diagnostic tool that helps you determine if the screen
abnormality you are experiencing is an inherent problem with your monitor, or with your
computer and video card.
1 2 3 4 5
To run the built-in diagnostics:
1. Ensure that the screen is clean (no dust particles on the surface of the
screen).
2. Press and hold Button 4 for four seconds, a menu appears on the screen.
3. Select the built-in diagnostics option. A gray screen appears.
4. Carefully inspect the screen for abnormalities.
5. Press Button 1 on the front panel again. The color of the screen changes to
red.
6. Inspect the display for any abnormalities.
7. Repeat steps 5 to 6 to inspect the display when it changes to green, blue,
black, white, and text screens.
The test is complete when the text screen appears. To exit, press Button 1 again.
If you do not detect any screen abnormalities during the built-in diagnostic tool, the
monitor is functioning properly. Check the video card and computer.

5. Trouble Shooting Instructions
Common problems
The following table contains general information about common monitor problems you
might encounter and the possible solutions:
Common
symptoms
What you
experience
Possible solutions
No video/
Power LED off
No picture • Ensure that the video cable connecting the
monitor and the computer is properly connected
and secure.
• Verify that the power outlet is functioning
properly using any other electrical equipment.
• Ensure that the power button is depressed fully.
• Ensure that the correct input source is selected
in the Input Source menu.
No video/
Power LED on
No picture or no
brightness
• Increase brightness and contrast controls
through OSD.
• Perform monitor self-test feature check.
• Check for bent or broken pins in the video cable
connector.
• Run the built-in diagnostics.
• Ensure that the correct input source is selected
in the Input Source menu.
Missing pixels LCD screen has
spots
• Cycle power on-off.
• Pixel that is permanently off is a natural defect
that can occur in LCD technology.
• For more information on Dell Monitor Quality
and Pixel Policy, see Dell Support site at:
https://www.dell.com/support/monitors.
Stuck-on pixels LCD screen has
bright spots
• Cycle power On-Off.
• Pixel that is permanently off is a natural defect
that can occur in LCD technology.
• For more information on Dell Monitor Quality
and PixelPolicy, see Dell Support site at:
https: // www.dell.com/support/monitors.
Brightness
problems
Picture too dim
or too bright
• Reset the monitor to factory settings.
• Adjust brightness and contrast controls through
OSD.
Safety related
issues.
Visible signs of
smoke or sparks
• Do not perform any troubleshooting steps.
• Contact Dell immediately.

5. Trouble Shooting Instructions
Common
symptoms
What you
experience
Possible solutions
Intermittent
problems
Monitor
malfunctions on
& off
• Ensure that the video cable connecting the
monitor to the computer is connected properly
and is secure.
• Reset the monitor to factory settings.
• Perform monitor self-test feature check to
determine if the intermittent problem occurs in
self-test mode.
Missing color Picture missing
color
• Perform monitor self-test.
• Ensure that the video cable connecting the
monitor to the computer is connected properly
and is secure.
• Check for bent or broken pins in the video cable
connector.
Wrong color Picture color
not good
• Change the settings of the Preset Modes
in the Color menu OSD depending on the
application.
• Adjust R/G/B value under Custom Color in
Color menu OSD.
• Change the Input Color Format to PC RGB or
YPbPr in the Color menu OSD.
• Run the built-in diagnostics.
Image retention
from a static
image left on
the monitor for
a long period of
time
Faint shadow
from the static
image displayed
appears on the
screen
• Set the screen to turn o after a few minutes
of screen idle time. These can be adjusted in
Windows Power Options or Mac Energy Saver
setting.
• Alternatively, use a dynamically changing
screensaver.

5. Trouble Shooting Instructions
Product specific problems
Problem What you
experience
Possible solutions
Screen image is
too small
Image is centered
on screen, but
does not fill entire
viewing area
• Check the Aspect Ratio setting in the
Display menu OSD.
• Reset the monitor to factory settings.
Cannot adjust
the monitor
with the
buttons on the
front panel
OSD does not
appear on the
screen
• Turn o the monitor, unplug the monitor
power cable, plug it back, and then turn on
the monitor.
No Input Signal
when user
controls are
pressed
No picture, the
LED light is white
• Check the signal source. Ensure the
computer is not in the power saving mode by
moving the mouse or pressing any key on the
keyboard.
• Check whether the signal cable is plugged
in properly. Connect the signal cable again, if
necessary.
• Reset the computer or video player.
The picture
does not fill the
entire screen
The picture cannot
fill the height or
width of the screen
• Due to dierent video formats (aspect ratio)
of DVDs, the monitor may display in full
screen.
• Run the built-in diagnostics.