Hi,Geoff.
The monitor is dead and only responds to the on/off button.
Yes we can buy a refurbished board from China but from Philips
it will be more expensive only for a couple of hundred euros and real one year warranty.
My old Samsung Galaxy S3 "killed" two memory cards smile
Of course another option is to find (or who agree to give) any working monitor of this series and make a copy of the memory card.
But the most interesting is information about the purpose and content of this memory card...