90V AC potential to ground, occasional tingling sensation

[JohnW2]

double the length and vulnerable and additional loose connexion point. ... Been there, been there and been there

I've quite often been there, too - but in my case without any adverse consequences that I can recall

 

[SUNRAY]

I've quite often been there, too - but in my case without any adverse consequences that I can recall

constantly plugging and re-plugging those connectors causes enough problems without introducing a second.

 

[JohnW2]

constantly plugging and re-plugging those connectors causes enough problems without introducing a second.

If the second one cannot be "plugged and re-plugged" because of the Superglue, it doesn't introduce any further plugging/re-plugging' problems

 

[SUNRAY]

If the second one cannot be "plugged and re-plugged" because of the Superglue, it doesn't introduce any further plugging/re-plugging' problems

As I mentioned earlier...

Been there.

And the last thing anyone wants is sh/tty clicks and bangs during a live show everytime an effects pedal is touched.

An intermittent fault on the average bit of domestic kit basically doesn't matter a toss but I'm guessing this list by OP will, even if currently only intended for their private bedroom antics, be used for performances to others. If my experiences of hosting up and coming wannabes (no disrespect implied) on public arenae and the regular botch repairs we assist with to get their faulty kit workable is anything to go by, then simple little correct solutions such as this goes a long way to being on the right road.

 

[SUNRAY]

Hi,

I have various DC-powered devices (guitar effects pedals and related gear). They are powered with 9V, 12V or 18V centre-negative DC power supplies. I also have AC-powered amplifiers that I have built myself. Yesterday, for the first time I can recall, I felt a mild shock/tingle when touching the chassis of an amplifier (which is metal and connected directly to ground via the earth wire of its power cable) and a metal part on one of the guitar effects pedals.

I’ve been trying to work out what’s going on ever since. (Below, when I say “true earth”, I generally mean I stuck a multimeter prong into the earth prong of a wall outlet.)

I know the amp chassis is grounded properly. I get multimeter beep continuity between the amp chassis and true earth. I measure zero DC or AC potential between the chassis and true earth.

However, sometimes (but not always…) I can measure 80-100V AC potential between the amp chassis on the metal part of the (DC-powered) effects pedal. I assume this is what’s causing the tingle.

I think that, by design, the effects pedal cannot be properly grounded, because it is powered by a two-pole DC barrel plug which in turn is powered by a wall-wart power supply that has a plastic earth prong.

In fact, if I measure AC voltage potential between either prong of the DC power adapter (when plugged in) and true earth, I get 90V AC consistently. I don’t fully understand this, but I am guessing it has to do with the way the DC power adapter turns AC into DC without a reference to earth? (I have done this test - one prong in the earth of a wall outlet, the other on either pole of the 9V DC plug – in different parts of the house, and it always measured 90V AC).

Then, I had the effects pedal unplugged and I felt another tingle. So I measured, and for a time I had 90V AC between that and true earth even when it wasn’t plugged in. I can’t get my head around how that happened, and it isn’t always like that.

The only other thing I can think of perhaps being relevant, is that both the amp and the power supply for the effects pedal are plugged into the same 4-gang extension lead, which has “surge protection” and a single physical on/off switch.

I’d love some help to understand what’s actually going on here. There’s a part of me that thinks something must be wrong with the wiring in the house but there‘s no other reason to think so (and I have used wall socket tester to look for ground faults or reversed live/neutral and it comes up fine).

Thank you,
Martin

Something suddenly struck me like a wet cod round the face...

With all the other issues aside, I'd be looking at where the inconsistency is within your system.

I slightly struggle with why there is no link within your interconnexions to effectively join the units together and mitigate any stray voltage within a power supply.

Do you see 90V between your guitar jack and 'proper earth'?