Venue 11 desktop dock no HDMIoutput

Hi Guys,

Picked up a second hand Venue 11 model 7130 MS, with Windows 10.

Also came with desktop dock (model K10A) and keyboard (model K12A).

I can get HDMI out from the Venue to a monitor without problems.

However, I cant not get HDMI out from the desktop dock when the Venue is docked. The HDMI still works from Venue when docked, but not from the dock.

I have done some googling and found a common problem.

Is the dock faulty? Do I need 'dock' software?

I cant update dock firmware as you must have a HDMI display to do that.

If it is a bad batch of docks, how do I tell which ones are not bad, if I go looking for another?

TIA