Forum: Analog Circuits Samsung SA450 monitor failure Check Signal Cable

von Patrick K. (herrk)

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I am seeking assistance in repairing a faulty 24" SAMSUNG SyncMaster 
SA450 monitor. The exact model is S24A450BW.

I purchased two identical monitors of this model back in 2012, and I 
have been using them in a dual monitor setup via DVI ever since.

Due to the pandemic, I have recently connected them to an HP business 
laptop using an HP docking station with DVI-to-DVI adapters. I have 
never encountered any issues until last week.

Usually, when I finish working, I leave the desk momentarily, causing 
the laptop to go into sleep (hibernate) mode. The monitors then enter 
standby mode (indicated by blinking power LEDs) as soon as the 
screensaver activates.

However, on that particular morning, when I powered up the laptop, I was 
greeted with the usual login prompt, and I successfully logged in.

There is a known issue with my company's VPN where, sometimes, it fails 
to establish an online connection when the laptop wakes up from 
hibernation. This issue is indicated by a red symbol on one of the 
taskbar icons.

To resolve this, I usually have to reboot the laptop. So, I did that. 
But then, I noticed that one of the monitors kept displaying the message 
"Check Signal Cable" (in German: "Signalkabel prüfen" and "Digital" due 
to the language settings).

Even after reaching the login screen and logging in, the monitor 
continued to show the "Check Signal Cable" message. However, I could 
still move the mouse across the "invisible" extended screen, indicating 
that the laptop detected it.

Initially, I tried turning the monitor off and on again, but it didn't 
work. Next, I checked and swapped the cables and adapters, but had no 

To ensure that it wasn't a simple issue, I connected both monitors, one 
at a time, to another laptop that I know is in working condition. 
Surprisingly, one monitor continued to fail while the other one worked 
as expected.

I came across a YouTube video 
(https://www.youtube.com/watch?v=EjTC0_Qk5nY) that claimed to fix the 
same issue in a similar model by installing a newer firmware. I tried 
the same approach, but the firmware updater software informed me that 
there was no update available.

From the beginning, there was something strange: the monitors have 
buttons to switch between inputs (DVI vs. VGA). I initially attempted 
this, but the screen remained blank for a while before displaying the 
"Check Signal Cable" message again.

There is also a Menu button for the on-screen menu. Similarly, the 
screen stayed blank, but it took much longer to display the menu.

I discovered that I could navigate the menu "invisibly." Even the 
confirmation of options was indicated by the power LED flashing.

Finally, I managed to see the on-screen menu, but it was shifted far to 
the right and bottom, so only a part of it was visible. On another 
occasion, the menu appeared on the screen but was not centered as 
expected. Unfortunately, without a signal, the menu is limited to a 
single setting for the VGA input. The "Reset Settings" option is grayed 
out unless there is a signal.

What could be causing these issues? Is it possible that the flash memory 
of the monitor is failing? (I found the schematics, and there are EEPROM 
and flash components on the board).

I also discovered an RST (Reset) pin on the PCB, but it is covered by a 
soldered shield. Should I attempt to short it to GND (ground)?

Any assistance would be greatly appreciated.

: Edited by User
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