[sdiy] Ground = -15V ????

[Rutger Vlek]

Hello everyone,

I'm having a strange problem with a synth i'm building. It's just finished 
and works fine, but I found out that there's a voltage difference between 
the synths ground and the ground of my mixer. The difference is 15V!! That's 
exactly the voltage the powersupply of the synth is generating. Compared 
with the ground of other synths or the wall outlet ground the difference is 
also 15V! This means that connecting a synth to the external input i made on 
my synth makes that current is flowing between them. I don't like that... 
and I get lots of weird behavior when i make the connection.

I have a symetrical power supply in the synth that gives +15V and -15V. I'm 
using a power distribution board identical to the Oakley Sound Dizzy board. 
All panel grounds, board grounds and digital grounds come together on the 
distribution board and are connected to the power supply's 0V.

I am using a 3-pin mains power connector connected to a grounded wall 
outlet, but internally i'm not using this third pin. Should I?

Greetings,

Rutger