Small shock from pos earth pedal

Frequently asked questions regarding powering your pedal.

Small shock from pos earth pedal

Postby stupidsignup » 30 Jun 2013, 12:02

Ok I have A level physics (an exam at age 18 in the UK) so have smattering of theory.
I HAVE GOT MY HEAD AROUND POSITIVE EARTH/NEGATIVE EARTH - no problem..

But why do I get a shock from my wah wah when I'm powering it from a mains 9v PSU?
The PSU is in one wall socket, I'm sat holding my guitar which goes into an amp, plugged in to another wall socket.
Obviously this is a low 9 volt shock but I'm surprised I can feel it quite strongly, like an ant bite.
I suppose I'm just making a circuit between the +9v outer case of the wah to guitar based earth via the strings.
But I don't see other people complain of this?

(I have a healthy fear of electric shocks having nearly killed myself age 7)
stupidsignup
 
Posts: 5
Joined: 18 Jun 2013, 23:01
Has thanked: 0 time
Have thanks: 0 time

Re: Small shock from pos earth pedal

Postby Liquitone » 15 Jul 2013, 09:50

A Wah is a negative earth pedal and its v-, not its v+ should not be in contact with the casing. In a positive ground pedal it's the v+ that's connected to the case but the 9v+ ground being a reference point you should not be getting a shock when you touch a positive ground case and your guitar. You are basically touching the same reference point because the voltages of both the positive ground and negative ground pedals are not directly touching your guitars hardware or pedal's enclosures.
I don't have a degree so there are maybe others who understand and can explain it better than me.
That said, I have had mild but annoying electrical shocks when touching my pedals when I ran a Pedalboard with a combination of 9v,12v,18v and 24v negative ground and 9v positive ground pedals on it.
I made very sure everything was in good shape, especially the amps and power-supplies and it was, but I was still getting these mild shocks, that felt a bit like static discharge.
User avatar
Liquitone
Breadboard Brother
 
Posts: 71
Joined: 20 Jan 2010, 00:04
Location: Groningen, The Netherlands
Has thanked: 11 times
Have thanks: 11 times

Re: Small shock from pos earth pedal

Postby Govmnt_Lacky » 15 Jul 2013, 15:05

DO you run active pickups?

If not... Do you have your guitar's bridge grounded?
Govmnt_Lacky
Resistor Ronker
 
Posts: 380
Joined: 24 Mar 2011, 14:00
Has thanked: 11 times
Have thanks: 42 times

Re: Small shock from pos earth pedal

Postby boblob » 27 Apr 2014, 12:47

That doesn't sound too encouraging.

You generally shouldn't feel 9V as it's not enough to break down your skin's resistance. IIRC, you won't feel anything under ~ 18V, so I would think there's something else going on here. If I were you I'd get everything properly checked out.
boblob
Breadboard Brother
 
Posts: 87
Joined: 27 May 2010, 21:53
Has thanked: 8 times
Have thanks: 10 times

Re: Small shock from pos earth pedal

Postby DrNomis » 11 May 2014, 22:08

It could be that the 9V plugpack you're using is a Switchmode type, they do tend to cause earth shocks...... :thumbsup
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
User avatar
DrNomis
Old Solderhand
 
Posts: 6865
Joined: 16 Jul 2009, 05:56
Location: Darwin,Northern Territory Australia
Has thanked: 123 times
Have thanks: 384 times

Re: Small shock from pos earth pedal

Postby Lucifer » 11 May 2014, 22:37

My wife gets a big shock every time I bring home a new pedal :twisted:
”Sex is great - but you can’t beat the real thing !” - The Wanker’s Handbook
User avatar
Lucifer
Cap Cooler
 
Posts: 671
Joined: 06 Apr 2011, 13:59
Location: Dorset, UK
Has thanked: 104 times
Have thanks: 95 times


Return to Power

Who is online

Users browsing this forum: No registered users and 2 guests