Poly-800 MK-1 memory backup battery 



The Poly-800 didn't have any dedicated battery for keeping the patch
memory.
(The MK-2 and the EX-800 have backup battery as standard.) If you
remove the power and C-cells at the same time the patches are lost.
This modification shows how to add a dedicated backup battery. After the
mod the patches will be kept at all times.
However, beware that the firmware of the MK-1 has a bug which cause a
total crash with memory loss when hooked up to certain sequencers.
If you have this problem, try to connect the Poly-800 after the sequencer is
started.


The mod: 

     Open the Poly-800 by removing all screws at the bottom. Locate
     the processor board. This is the large circuit board next to the
     battery compartment. 
     In the upper left corner you'll find Resistor R1 and Diode D1.
     Remove these. (Just cut the legs, but leave as much as possible of
     the D1 legs, see next steps.) 
     If you have a late revision MK-1 there will be two fairly large solder
     "islands" in the center of the board. The battery is mounted here. 
     If you have an early revision you wont find this. The battery must
     then be connected by wires, the plus to the junction between R1/D1
     and the minus to the other leg of D1. 
     Any 3V lithium with solder lugs can be used as long as it is not to
     big physically for mounting to the board. A wristwatch type (2025,
     2032) is fine. 

That's all!