HDMI KVM Switch – Laptop Not Recognized

hdmikvm-switchmultiple-monitorswindows 10

I need to use my single monitor (HDMI, Samsung SyncMaster B2430) and keyboard / mouse (USB, Microsoft Sculpt Ergonomic) with 2 laptops, to be able to switch between the two easily with one click of a button.

My 1st laptop is my old Samsung Series 9 NP900X4C, running Windows 10 Home (with a micro HDMI port).

My 2nd laptop is a Dell Precision 5520, running Windows 10 Enterprise (with full HDMI port)

Up till a few months ago I was using a cheap HDMI Switch, (3-port Duronic).

It was working fine (I was switching the keyboard separately by swapping the dongle), but at some point it stopped recognising my Samsung Laptop. I thought it was something wrong with the HDMI switch, given its such a cheap device, and didn't bother doing any more troubleshooting.

Instead I went ahead and bought a Bowu 2 USB HDMI KVM-Switch. This one also takes USB so with one button I also switch the keyboard and mouse, not just the monitor.
The USB switching works perfectly between the two laptops on the new KVM switch.

The problem is that when I connect my Samsung laptop through the new switch the monitor does not recognize the signal. But when I connect them directly it works, so I know that the HDMI port on my laptop is not busted. It is also strange that both HDMI switches are behaving in this way. 

Samsung Laptop -> Monitor = OK

Samsung Laptop -> KVM Port 1 -> Monitor = NOK
Dell Laptop -> KVM Port 2 -> Monitor = OK

Dell Laptop -> KVM Port 1 -> Monitor = OK
Samsung Laptop -> KVM Port 2 -> Monitor = NOK

I also tried swapping cables to eliminate the possibility of a faulty cable.

Given that this used to work before with my old HDMI switch, and suddenly it stopped, I am starting to suspect it must be some driver or windows update issue that screwed this up, or some display setting which somehow is not compatible, although I don't recall changing any resolution or display settings.

Is there any way or any tool I could use to debug what is going on when the HDMI handshake takes place between my laptop and monitor through the KVM?

Best Answer

After a long exchange with the poster, and quite a few tests, the relevant points that are left are listed below:

  • The Samsung Series 9 no longer works through two different KVMs
  • Two other computers have no problem getting through both KVMs
  • The Samsung Series 9 can directly connect to the monitor, just not through any KVM.

My conclusion is a hardware degradation on the Samsung's video adapter. Perhaps a weaker video signal has some problem punching through a KVM.

As the video adapter is integrated into the motherboard, it's likely not worthwhile to further invest in this computer.

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