Vintage Synth Repair

Hello. I'm new here. I'm also pretty ignorant when it comes to 
electronics and synthesizers. So that's why I'm here. I have a Korg 
Trident Mark II, and a problem. First off, I got it for free, with a 
disclaimer: the previous owner dropped it or something, and now it 
doesn't make any sound. Peculiar. So I took it home and plugged it 
in and I couldn't get any sound from it. But upon playing around 
with it further, I could get a few sounds, but nowhere near the 
apparent capabilities of the synth. But the most annoying part was 
that every key in the keyboard played the exact same note. So, right 
now, the joystick and delay vibrato doesn't work, the strings 
section doesn't either, the brass section is very limited, and the 
synth section doesn't seem to respond appropriately when I turn the 
knobs. But when it does make sound, it's clear and loud, which makes 
me really want to solve these problems. I've inspected the circuit 
boards and the wire connections and everything seems intact and free 
of anything broken or scratched or anything. Now I am aware that 
there is a cassette interface on this synth. Is there some way that 
loading some sounds from the same model of synth would help me out? 
Is there some factory recordings that they would use to initially 
load these synths? So as of right now, I am investigating this 
possibility and am wondering if anyone could direct me toward some 
of these recordings on any medium like cassette or wav files or 
anything so I can give this a shot. However, if someone knows a 
better idea, I'd love to hear it. Thanks!
Craig Storm