Hi peoples. My friend has an Sp-505 that he's had for quite a few years now. I'm thinking of buying it from him but there's a problem that started a while ago. The effects knobs don't work right. They glitch out and the value skips all over the place. Has anyone had this happen? Is there anything that can be done? Thanks.

haven't had that happen, but it could be a harsh scene.

before buying it, get some contact spray (like you use to clean computer parts) and spray it around the knobs. could be grit and gack in there.

if it continues with the skipping, i'd skip on buying it.

are they pots (limited turn range) or encoders(keep turning forever in both directions)?

pots will have to be replaced most likely, (you can try spraying them with air though)
encoders it will depend on whether they are 'clicky' or optical based.. optical ones can get jumpy just from dust/etc blocking the sensors..
clicky encoders its hard to say... probably have to replace again

they are pots.

maybe pick up an otherwise busted 202, 303, 505 for cheap and swap in the parts?

thanks, for some reason I thought the 505 had encoders.. dunno why lol

you should be able to get a few pots for a dollar or 2 each,
if you open up the case you will hopefully find the specification written on the side of the pot's base - it will say something like B10K - the letter at the start is the type - A or B usually - then 10K is the maximum resistance (10,000 ohms).
In addition to that you need to match the shape of the base where the pins come out and the shaft length.

if you don't know how to do this kinda thing for yourself/have a friend who knows what they're doin, even paying an electronics guy to do it should not be too big a deal.

Unless you get a really good deal, I'd probably just pass on it and hang out for one on ebay.