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

[René Schmitz]

Hi Rutger,

Rutger Vlek wrote:
> 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'd unconnect everything from the synth, and check the GND of your 
external connections jack against the GND point at the PSU. Could be 
that there is some accidental connection between either supply rails and 
your case/jack GND.

> 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?

If the transformer you're using is haveing double insulation then that 
should be ok.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159