Poly 800 MKII

Purchased in 2017 from eBay, this synth arrived and was in average cosmetic condition. It powered up but there was no output. Half the screws were missing, which is never a good sign.


I downloaded the factory sound banks in sysex format and sent them to the Poly. All the sounds were there and the synth now appeared to be working. The coin backup battery looked like it was a little old, so I replaced this. Someone also must have replaced the voltage regulator and couldn't be bothered desoldering the old one. The new one is just bodged to the old ones legs.

I decided to do the not very aptly named 'moog slayer' mod which involves replacing the internal filter adjuster to outside pots

I also did the FM mod, which produces a kind of pseudo FM modulation effect.

Whilst this synth has plenty of controls and is a nice cheap synth to mod, it's nothing special sonically. I find the sound has no movement in it and is pretty flat. I shall install an onboard chorus to see if that can liven things up a bit.

Service manual for poly 800 II

Factory banks in sysex format