Sorry I can't help you, but I am curious why you can't use a new board?
Looking for HTP Vision 3 Board.
I have a customer who needs a circuit board for a Vision 3 multi boiler control for munchkin. It needs to have a date of manufacture sometime before the end of 2005. The older ones would modulate boilers in parrallel, the new replacement controls only modulate sequentially. I need to find one of the older ones if any-one has access to one, can be used, as long as it's functional. My email is colin@trimech.ca
The programming was changed due to a patent conflict, The new ones control the boilers differently, and in my case create short cycling.