This is so far just a thought in my head.
The PG-800 is a programmer for the JX-8P (and JX-10 and MKS-70), but I don't have a programmer.
Since my JX-8P is broken I can't really test any programmer so it's not really high on my priority list at the moment. Especially since I have already started my Matrix editor and have 4 synthesizers to repair.
Anyway, I saw the schematics for the PG-800 and it looks really simple. Perhaps it would be a better "first project" than the Matrix editor but at least the Matrix-1000 is working :)
So.. This will have to remain an idea until I at least fix the JX-8P and probably until I have gotten some more things on my todo-list done...