Is the battery from your Korg Poly61 original, or has is been replaced? There is a high risk of leak & internal damage with this model, so it should be checked before the sale. Ayway, it will be the first question a potential buyer will ask...
-Roland JX3P+PG200, D50+PG1000, Juno 6+106, MKS50/70, JP8080, U220, MVS1, MDC1, MSE1, TR-707
-Korg M1R, MicroKorg, Micro X, Kaossilator/Pro, Monotron X3
-Yamaha DX7, TX816, TX81Z
-Future Retro 777, DSI Mopho, EMU Proteus FX