Casio MT-100 Barely Audible

[casiotonemt100]

I've got a Casio MT-100 which is putting out sound but you can just barely hear it. I've tried removing the linear slide potentiometer, taking it apart, cleaning, and resoldering it. No improvement. There's no change where I'm getting sound through the speaker on the keyboard or through headphones. Also, volume doesn't change no matter how I slide the potentiometer, but I can detect a change in tone when I twist the tone knob.

[Gordonjcp]

Perhaps the audio amp is faulty?  Have you tried feeding the signal from the wiper of the volume pot to another amp?