Refurbish your old synth with Liquid Wrench!
No I'm not the marketing director for Liquid Wrench
but the red can (silicone spray) is great for those buttons that stick on your old synth. I used it on my Korg X3 and it works great, it works like new! I also sprayed a rag and covered all the plastic and metal parts then lightly buffed it and it looks new as well. It's safe for painted surfaces as well.
If I were not a physicist, I would probably be a musician. I often think in music. I live my daydreams in music. I see my life in terms of music. Albert Einstein