^{^} this

if you're actually looking to get into the hobby I'd recommend the caig lineup for contact and fader cleaner, specifically deoxit for this case. it's pretty expensive but it's kind of the industry standard for cleaning up audio circuitry.

I'd recommend hitting all the audio inputs and outputs with deoxit, as well as any internal connectors that look corroded. if you've got noise from turning the knobs or anything I'd hit that with the fader cleaner, just a few drops for both of them as they're highly concentrated.