PX-1 _ Low volume and sough

Hello everyone!
Absolute newbie here.
I'm now learning Keys and been playing drums for about 10 years now.
My technical understatement is mediocre to good.

My problem:
I got a used PX-1, which is one hell of a beauty and i managed to fix the power cord which someone torn out.
So i got power back in this thing.
The thing is, that the volume is very quiet from the phones out and the line outs. Also there is a "noise carpet" either when the volume is high or low. Tomorrow i get two XLR to Chinch cable to plug it into my old harman&kardon amplifier to test if the XLR output got the same problem.
Is it maybe a problem with the preamp inside the PX-1? I can not imagine that the volume is that quiet out of a phones output.

Best wishes to all of you.