Making a Yamaha ADP1 ??

Hey,
 

 I've seen in this mentioned in this topic chat: https://groups.yahoo.com/neo/groups/YamahaDX/conversations/topics/18948 https://groups.yahoo.com/neo/groups/YamahaDX/conversations/topics/18948
 

 has anyone gotten anywhere with making a DIY ADP1 ? 
 

 I have a DX7S and I'm considering making makeshift one with a riser/donor card. 
 

 It would be great to own an ADP1 as an example but of course they are rare/expensive.
 

 As I understand it there is no schematic available to detail the crossover between RAM1 and RAM4 ? which the adp1 achieves. 
 

 Any info would be much appreciated?
 

 @aerobaticant ?