Electric shock!

[Ninecows]

My MatrixBrute gives me an electric shock once in a while. Several times per session! I have tested thoroughly with a multimeter and all the bare metal parts has a good and solid connection to ground. The pitch/mod-wheel does not and obviously I cannot measure on the painted parts without scratching the paint.

It is however from these areas where it will give me a shock. Sometimes it’s jus small and sometimes it really unpleasant.

The other equipment I have with same ground connection doesn’t have an issue. It’s connected to my audio interface with two jacks and my Mac with USB. Good connection between the ground on these and the MatrixBrute as well.

Of course it’s just outside the 3 year Thomann warranty, but this is really unpleasant and possibly dangerous?

The unit has just been on a shelf in my studio since day 1. Never moved or anything.

[DrJustice]

When we talked about this over at GS, you mentioned the possibility of it being a static shock. If you touch a metal part so you get the shock, and then keep holding it, can you feel a constant current flow? If so, it's definitely not static, and I'd open a support ticket to get the experts at Arturia in on the diagnosis.

[Processaurus]

That’s worrisome! What country are you in, like what electrical plugs do you use?

Is the shock a “pow” (DC) or a “vibration” (AC)?

Can you beep continuity with the multi meter from the chassis to the safety ground on the plug? If the plug is damaged it can make the ground float on the synth’s chassis.

Do you have a plug tester to test the outlets in your studio? They’re cheap at the hardware store. Floating safety ground can cause shocks with functional equipment.

You can measure electrical potential between pieces of gear on the AC or DC setting (usually AC for wiring problems) by putting one lead on the chassis of one piece of gear, and the other lead on the other piece of gear chassis. Also works for measuring if the safety ground between two outlets is at the same potential, which can cause shocks if they are wired through the building to different grounds- a classic scenario is the guitar amp is plugged into one circuit, and the PA is plugged into another, and it shocks the guitar player when they step up to the microphone, because their mouth is connecting the grounds of different parts of the bui,ding and some current flows back through the guitar strings and cables to the amp’s safety ground.

[Ninecows]

yeah... its shocking.

It happens pretty randomly and if I keep holding on e.g. the mod-wheel I don't feel the current flowing, but if that's because its small (but builds up over time when I'm not grounding it) or because its me that's just charged is hard to know. I would say it feels more like DC than AC, but that's just a guess.

Anyway. I live in Denmark. We have these three hole outlets. The standard schuko plugs will not connect to ground through these, so I use an adapter like this: https://progrossist.dk/produkt/hybridstikprop-pindjor-dk-lgraa/

With my multimeter I can beep through continuity from any bare metal part on the chassis (e.g. the hinge, sleeve on jacks, screws on the side etc) to the ground. Also to the ground on the outlet next to the outlet I'm have connected the synth to. And to basically all other non-painted/oxidized metal parts in the studio. So I believe the ground is solid enough. I have also tested potential (so not continuity) between a metal water pipe (coming out of the real dirty underground) and the ground in my outlets. That's also 0 V. And everything is connected to the same ground. The charges actually seems to come from the parts that are painted and/or the mod-wheels. So that actually indicates that a charge can build up on these areas. I have not (yet) tried getting a zapp! from the areas that have a good ground connection.

I have also tested potential between my different gear. And it turns out that there is more potential between my left and right hand than between of my gears. And we're talking mV here... so not a lot.

If I have time this evening I will continue my search - Will try to measure potential between the different parts on the matrix brute it self.

[Ninecows]

...and I don't have a plug-tester. They are not cheap, nor available in the hardware stores in Denmark it seems. Normally you would call an electrician and have him test it for you (for a small fee of ~100 USD)

[MajorFubar]

Sounds more like static build up to me. Bet you're wearing shoes that build up a lot of static, and when you go near something that's metal and grounded like the MXB fascia, you're discharging yourself with a bang. (This is also usually worse in winter when it's cold)

[DrJustice]

...
It happens pretty randomly and if I keep holding on e.g. the mod-wheel I don't feel the current flowing, but if that's because its small (but builds up over time when I'm not grounding it) or because its me that's just charged is hard to know. I would say it feels more like DC than AC, but that's just a guess.

The wheels are not grounded. Do you also get a zap from those?

If there is AC current flowing, you'd feel a distinct tingling sensation.

However...

The charges actually seems to come from the parts that are painted and/or the mod-wheels. So that actually indicates that a charge can build up on these areas. I have not (yet) tried getting a zapp! from the areas that have a good ground connection.

All things described so far does sound like static. As The Major says, it can be worse in the winter. Where I live we're well below 20% relative humidity at times, and my cats and me frequently exchange static shocks, whereas in the summer there's none at all. Again, as per The Major's observations, shoes, carpets and so on can play a role, again possibly exacerbated by dry winter air.

You wouldn't happen to have some grounding bracelets and leads? If not you can get one for 100kr or so. If you grounded yourself to the MxB chassis with one and observed, that might help in pinpointing this.

[Ninecows]

The wheels are not grounded. Do you also get a zap from those?

Yes... mainly the wheels and the painted parts. Never (or not yet) from the bare metal that has connection to ground.

But I will do experiments with my little multimeter and see if I can measure where the charge is building up - me or the MxB 

And I don't wear shoes in the studio... its ceramic tiles on the floor. Not carpet. But apart from that I agree that me being charged is just as likely, so I will investigate...

[Ninecows]

Ok... This is just SO fun to write: I'm guilty as charged 

Longer story... it's got to be static electricity and I am the guilty one. My multimeter can measure around 400-900 mV (not V, but mV) on me compared to ground when I get up from my chair to play the MxB. As long as I'm sitting still I have no significant charge. And the MxB is the only equipment where I'll have to get up.

I have also tried to measure on the MxB. Here the potential between ground and the mod/pitch wheel and the painted parts is nothing. 0 V. Not even a few mV.

So even though it's not a lot with <1 V it's got to be me. Perhaps my multimeter has trouble detecting larger charges on my fingers. At least I'm the one with the biggest charge

I will find ways to strap my self to ground. Perhaps I can do it a simple wire or get one of those recommended by Dr Justice... just have to make sure I connect it to ground and not the live one or this will be my last post here

Thanks for all your help.

[thark]

I would be interested to know how this finally works out for you. Here on the Canadian prairies, the humidity in the winter is very low … 20% to 25% and I sometimes get a small shock when touching a piece of gear. In fact, when I was working in a lab with super expensive equipment I got into the habit of always grounding myself before touching something. I do this in my studio too.

Keith