Audio Systems: Yamaha AX-700u scratchy bass control, scratch noise, domino effect

Question
Hi Garry,
I bought a Yamaha Ax-700u at a garage sale for 10 bucks! The unit works fine except it seems to have lost internal tone control bass intenisty and the bass control is scratchy when dialed. Also the Loudness dial makes a very slight scratch noise when turned.

I bypass the internal tone controls with an eq so it's not the most important thing.

But once things start to happen it usually becomes a domino effect...I like the tone of this amp and want to save it if possible.
Any info greatly appreciated.
Best regards,
Geoff

Answer
you need to give all your controls (volume, balance, tones,mode select and speakers, any,)a spritz of good control cleaner/lube such as de-ox-id and then vigorously work controls back and forth or in and out as the case may be. you will have to take the covers off first, some are accessible from top cover off, some with bottom cover off. good hunting....