92 Ensoniq KT76 piano - volume very low

Hi. I have a 1992 Ensoniq KT76 digital piano. It works, but the output volume is very very low, even when the volume fader all the way up (no noise from fader), either through earphones or the 1/4 jack outputs in the back, so i'm thinking something might be wrong with the amplifier inside? Could bad capacitors make the sound very low? The piano is old so caps are first thing i suspect.
Thanks!