Fault electric organ

I am new to the forum and more or less new to audio electronics bar circuit
bending a couple of things.
Yesterday a i bought a old Logan electric organ/synth
It turns out it is not fully working and they guy who sold it to me aint answering the phone so i'm gonna try fix it.Certain keys don't work with some sounds
the arp doesn't work or the chord section,there is a serious hum from the speakers.Volume pedal is dusty and fuzzy ah there is a couple of other things wrong too. anyway...

I opened it up and it is solid state a row of 12 boards marked for each note in the scale and one marked preamp.
there is alot of other stuff but it is hard to get in at.
I know nothing here so any suggestions would be great.
all i have is a soldering iron. gonna buy a multi meter later.

First, I would change all the electrolytic capacitors. Take pictures of the circuit boards and patiently make a list of the values you need, then make an order to your electronics supplier. Your hum in the speaker says you got a bad cap.

My friend bought a Cordovox 0622 synth on eBay and I got it to fix. Other techs in town didn't want to go near it. Replaced all the electrolytic capacitors ($40), many were all dried out and that fixed most of the problems. I left the oscillator boards alone (12 of them) as they only had one cap. A mouse ate some of the wiring and speaker cones, so I had to fix that too.

You have to be patient restoring vintage gear, one step at a time.