This keyboard had been kept in storage for a couple of years.  Unfortunately it was stored in a way that the battery leaked all across the processor board.

This shows the original battery a 3.6v Nicd.

With the edge connector out the way it was clear the  board had suffered greatly.   Because  this area had been disturbed the poly61 behaved very erratically. This connector had to be removed and cleaned extensively.  In fact the header connectors were so bad I ende up hard wiring  fresh cables to it, cut off the other connector and then joined them with a 25pin dsub connector.  One day i will replace with a proper connector.

Lots of time spent following traces on the ipad and wire linking open circuits.

So  now the synth was all working, and whilst it was in bits,  The Voice Of Saturn had some basic hijacking of the cutoff and resonance control.  Here you can see the aftermath of this operation.  The blue wires go to pots that were installed by the joystick.

Now the Poly61 was fully rocking it was begging for a midi upgrade.  I managed to find this awesome midi upgrade kit from Engineers@work.

1x pimped Poly61