# Potential diffrences question

Discussion in 'Electronic Basics' started by Anders N. Vinje, Apr 28, 2004.

1. ### Anders N. VinjeGuest

Hey.

I have this thing that puzzels me.
I have a question about electrical potential. Well this is the case.
I my bathroom i have wall outlets, they are of course groundet.. Everywhere
else in the house
there i no neutrual pin in the outlets. So i took a piece of wire and
connected to the neutrual
in the bathroom and brought in to my room. The i measured Dc and Ac voltages
between the neutrual
and the ground on my MIXER. At DC it said +- 1,5 v At AC it said 81,5
Volts!! Ok. So here there
is a big potential between the ground on my equipment and the
ground(neutrual) in the wall
outlets. Is this dangerous?? I also measured the same values between the
neutrual and my pc
ground(chassis).

I am also into music and i have three synths . I have one problem with one
of my synths.
Its a Korg Wavestation EX (digital). Sometimes the sound gets extremly
distorted and loud.
Then sometimes it just goes bact to normal. But sometimes it can go weeks
before that happens.
In my guess there is something wrong with the DAC becuse the sound is really
clipped and the
envelope of the sound is clipped. By that i mean when you play a sound, the
duration of time
before the sound decays is just cut suddenly. This is just a guess. I am
not a Electrical
enginner.I do fiddle around making preamps with opamps and making oscilators
as a hobby. I am
going to school this year to study to be bachelour in electronics. But now i
digress...
The point to all this is that i allso mesured the voltages between this
synths ground and the
neutrual. AC was 65 volts when the power was turned of and 115V!!! when it
was on. This is
really diffrent from all the other equipment i have. Then there was no
diffrence when the equipment was on or off. And lay at a stable 81,5 Volts
AC
I measured this several times. Does this indicate a potential problem??
Is this what makes the DAC goes ditstorted(in my guess)??? Maybe there is
connection inside the
synth between one of the hot wires and ground. Everything else works fine ex
cept the sound. Like menus and knobs etc. You can actually hear the orginal
sound in the back of the exstremly heavy distortion.

I really dont expect any to answer the problem with my synth but what is
floating around. I guess everything electrical should have be groundet to
the neutrual in the
building. I think its alot when there is 113 V AC diffrence or even 81,5 V.

Any thoughts??

Anders N. Vinje

Ps. You have to excuse my english i am only norwegian

2. ### SoerenGuest

Hi Anders,

Inside the power supply of many switch mode supplies is two capacitors.
One from phase to ground and one from neutral to ground. They create a
capacitive potential divider giving you half of 230V on the box if it is
not properly grounded (through an earth connection).

The reason for the lower readings is probably that smaller capacitors is

Yes, if you connect (sound) equipment with such a capacitor-filter, to
other equipment which is referencing its input ground to the box, you
might put 115VAC into an input - many a stereo has blown when people
connects their PC to their HiFi.

Don't think so, other possibilities seems more likely (dried out caps,
partly bad semiconductors etc.), try fault finding with a spray can of
"freeze".

You could try to feed the equipment with a multi-connector *with* an
earth-line (from the bathroom, if it is not isolated with a transformer
rated for just a shaver.
If that helps, call an electrician and get your mains outlets properly
earthed.

And you will have to excuse mine, I am only _human_

3. ### Rich GriseGuest

Sounds like an intermittent volume control pot. Or, it could just be
dirty. That'd be the first thing I'd check.

As far as the wiring issue, if you're not in the US, I really can't help
you, other than to say that neutral and ground are really two different
things - neutral is the return path for the load current, and ground
is for safety ONLY. The case should be grounded, so that if there's a
fault, it will blow the fuse, but the case should NEVER be connected
to EITHER side of the mains, no matter what country you're in.

Hope This Helps!
Rich