Arg!!...Help with grounding issue (??)...

[aidan7737]

Well I was at my regular ol' rehearsal venue just now and stepped up to the mic and got zapped. So frustrating.

I worked back through my signal chain testing with/without pedal board and it's power to just straight-in. Still had the problem.

Problem fixed when I ran an extension cord from another power outlet across the room for the amp and kept the same supply for the pedals (previously, they had both run from the same 4 outlet strip). Additional info: I believe the PA we use is powered from the same strip as I in turn get my amp/pedal power. After the successful change the PA and pedals would have been drawing from one strip, the amp another.

What could it be? The venue or me?

[darkbluemurder]

That happened to me, too. It was at a quite large gigging venue which looked as if it was set up properly. Normally this happens when the amp/pedalboard goes into a different outlet than the PA so the gear is at different ground potentials or even worse one of the outlets is not grounded properly.

If the amp/pedalboard and the PA are plugged into the same outlet then I would check whether one of the safety grounds is broken or defeated. This should never be done under any circumstances.

If all safety grounds were OK and all gear plugged into the same outlet then the next step is to check whether the outlet is properly grounded.

After that gig I always check with my VOM both for AC and for DC with one probe at the guitar bridge and the other on the microphone. Nothing ever happened since but this may be coincidence.

There is good information on www.guitarnuts.com (http://www.guitarnuts.com) on electrical shock hazard.

[John Phillips]

If both your amp and the PA are correctly grounded and plugged into the same extension strip (which is also correctly grounded) you cannot get a shock because the mic and the guitar strings are already connected together by the supply wiring grounds. Therefore, at least one of those things is not correctly grounded.

The pedalboard is likely to be ungrounded (by design, since its output is low-voltage and it shouldn't need to be), so that won't be it.

If moving the amp to a different outlet cured it, I would look at the outlet or strip the amp was plugged into as the most likely cause.

It's also possible that the amp and its wiring were perfectly grounded though, and it was the PA supply that's faulty. If you then moved the amp to another outlet with no ground, that could also cure it by removing the path to ground for the leakage from the PA.

It's always safest to have all your gear connected via grounded extension strips (that you or someone you trust have checked personally) to a single supply outlet - one plug, not even two on the same wall box if you can avoid it. That way everything on stage is certain to be at the same ground potential.

[jawjatek]

In old bars and dives a lot of times there is no ground. Always touch your guitar strings to the mike before your lips! Try to find a grounded outlet first, at least make sure the PA and amps are plugged in with the same plug orientation. Check for the item (amp, PA head, etc) that has 120 VAC on the frame measured with a voltmeter with one probe on a cold water pipe or concrete and the other on the frame metal. Flip the plug around or flip the ground switch on that item to fix it. As posted, having everything on one strip with plugs all oriented the same way is good practice, but you can still get zapped in ungrounded situations if one item has a ground switch flipped the wrong way.

Most guitarists with old Fenders don't know how to check the ground switch without a meter when playing on ungrounded mains - simply plug in a cord (without a guitar), turn amp on and up, and flip the switch. One setting will have noticeably more hum that the other. Leave switch in the quiet position.

I can't tell you how many house PAs in small bars I have found with the ground cut off the power plug.

I recommend a simple receptacle tester available at Home Depot, Lowes, many other places like this one: http://www.idealindustries.com/products/test_measurement/electrical_testers/circuit_tester_e-z_check.jsp

I keep one in my gig bag. Plug it in - two yellow lights? Good to go! HTH

[aidan7737]

Thanks for the advice darkblue, John and jawjatek, it's much appreciated :)

I was just taken aback because this is a rehearsal venue I've been going to week in week out, standing in the same spot with the same mic, plugging my same power strip into the EXACT same outlet even. I'll mess with it more next week and see if the problem persists. Thanks again!

[Popoon]

Could it be a case of the wrong trousers building up static and then jumping to earth?

Sometimes it can be undergarments or even shoes.