Korg DW6000 rebuild

Synth Repair
1

Greetings from Japan!

I am rebuilding a Korg DW-6000 I picked up recently.
(1) I’ve rebuilt the PSU so now it actually works.:grinning:
(2) I am going to change the battery holder just waiting for the part.
(3) I noticed that on headphones there is a mains hum 50hz over here that doesn’t change with volume settings. If I use the phono outputs there is no noise. Has anyone had that one before?
(4) It has been dropped on its end, right side during its life. The end piece has a couple of cracks in it and the top C key was floating. I gently removed the key, but there was a bit broken off at the back of the key and also one of the plastic posts built into the support has broken away, so I will have to make some kind of replacement post.
It looks like the top C key is hard to find. Does anyone know of a modern replacement for the top C on a DW6k?

Best regards

Tee.

2

Suspect a ground loop is injecting the hum.
An old trick was to have a cord with the ground not connected at the receiving end of the audio cord. Dont do that on all cords you need a reference ground between equipment but you dont need it on all cords as they common internally. Also since you just rebuilt the power supply…check all signal wiring is kept clear/away from the area and you may need to ad a low capacitance capacitor , between signal and ground to shunt unwanted noise check what is used near power pins on the chips to get an idea what designers think works best usually 15-22micro farad.

3

Thanks very much Ron will give that a try the next time I open her up.
Bit of a family crisis at the moment so it wont be a while yet.
I will return with my results.

Best regards and thank you.