Paul Apprich sent me this some time ago...

I've not tested it (by now) but it might help.

Here it goes:

Marc.
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>          The VR290DA uses composite sync if it has four BNC connectors in
> the back. What you will need to do is build a circuit that takes the
> horizontal and vertical syncs and mix them. Since these sync signals are
> TTL levels, I have used a 74LS86 exclusive OR gate to do this. 
> 
>                  1        
>          H---------\\~~~~\ 3      4     
>                  2  ||    |---------\\~~~~~\ 6    8    
>              gnd---//____/         5 ||     |------\\~~~~~~\ 10
>                   11           |----//_____/      9 ||      |-- out
>          V---------\\~~~~~~\   |             gnd---//______/
>                     ||      |--| 13    
>              gnd---//_____ /       
>                    12
>                                    7---gnd   14---Vcc (+5v)
> 
> 
> 	If any component of the signal need be inverted, move the 
> grounded input of the corresponding gate to Vcc. Any questions? :)
> 
> psapp@cnct.com - Is there life after Ultrix for VS3100?
> 
> 
>