Earth problem or not???

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Kaos is only a form of insanity
Member Since: Feb 03, 2005

The issue I have is on my practice room vocal pa set up.

I get small electric shocks from dynamic mics and even the rack mounting. No phantom power is on and I am concerned this will ruin my gear.

List of equipment>

desk UB2442 > inserts compresser and gate in series > output to EQ > amps > Speakers

The power sockets are all grounded centrally and i have check for earth fault on the power supply side and all is OK

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Ne'er ate 'er
Member
Since: Apr 05, 2006


May 24, 2008 01:23 am

Forget about ruining your gear. Electrocution is serious. The problem is probably due to a bad grounding within your desk, or between it and the wall. Get that desk checked out immediately by a qualified service person.

Hold 'Em Czar
Member
Since: Dec 30, 2004


May 24, 2008 11:27 am

are ya sure it's not static electricity?

try a small humidifier.

Ne'er ate 'er
Member
Since: Apr 05, 2006


May 24, 2008 12:01 pm

Hah, I didn't think of that.

Spray some Cling Free on yer feet.

Hold 'Em Czar
Member
Since: Dec 30, 2004


May 24, 2008 12:25 pm

yeah i was in a band and the singer was usin' a 58 and EVERYTIME he got too close ZAP! we all got a kick outta it.

Ne'er ate 'er
Member
Since: Apr 05, 2006


May 24, 2008 12:53 pm

But if you're standing still and get continuous shocks, better get your gear examined.


http://tbn0.google.com/images?q=tbn:F8sJ-X6O0QmwtM:http://theimaginaryworld.com/tic376.jpg


The Czar of BS
Member
Since: Dec 31, 2007


May 24, 2008 11:14 pm

If all of your equipment is grounded. And it's not static. You may have a chaise grounding issue, or, you have a power supply problem.

I have had the same issue with a Yamaha PM4000. The capacitors in the power supply had dried out, and were leaking AC on the ground. Not very fun.

Take a Voltage meter. Measure between chaise ground and signal ground. See if any AC exist.

Ne'er ate 'er
Member
Since: Apr 05, 2006


May 24, 2008 11:28 pm

Chaise=chassis?

Kaos is only a form of insanity
Member
Since: Feb 03, 2005


May 25, 2008 06:30 am

apologies for the delay in replying to all your helpful hints, Been caught up in an urgent work matter....

Herb - Cling Free??? I got cling film, but surely alluminium foil would be better !!!!! I could then have a new hair style without paying for a hairdresser

CHris - no humidity the room is dry as a bone (good air flow)

Rob - I'll check it out - now I hope i didn't leave my multimeter on one of my sites!

Prince CZAR-ming
Member
Since: Apr 08, 2004


May 25, 2008 09:07 am

Quote:
no humidity the room is dry as a bone (good air flow)


that could be the problem; you WANT moist air, as that lets ions travel back to their home, thereby reducing static buildup.

Cling free is an aerosol spray, that cuts down static charge on whatever you spray it on. So carpets and chairs are good candidates, to release the static buildup.


Kaos is only a form of insanity
Member
Since: Feb 03, 2005


May 28, 2008 07:08 am

OK I think I have found the problem, It seems to be a ground loop coming from one of the power amps. as my incoming supply is clean.

I tried another amp which has a ground lift switch and lifted the ground, now i don't have any shocks.

However my other amp doesn't have this ground lifting option, so I assume that the amp has a problem inside ???? Is it something I can check myself by means of a multitester or not.

Just as a side thought - It wouldn't be caused by having XLR outputs one end to unbalanced jacks the other (the amps only take jack inputs)

Hold 'Em Czar
Member
Since: Dec 30, 2004


May 28, 2008 04:28 pm

i'd bet that third lead on yer xlr cable that isn't beein' used is the ground....

is there any way to plug that mic into something else that already has unbalanced outputs? maybe some kind of DI box, or another preamp.

Kaos is only a form of insanity
Member
Since: Feb 03, 2005


May 28, 2008 04:36 pm

The output is from the EQ unit XLR to the amp 1/4 Jack unbalanced not the mics (although they are all xlr to xlr)

Hold 'Em Czar
Member
Since: Dec 30, 2004


May 28, 2008 04:37 pm

ok, does the eq unit have a groud lift on it?

The Czar of BS
Member
Since: Dec 31, 2007


May 28, 2008 05:15 pm

Wow, the amp is back feeding the whole system.

Not that unusual. I have seen this before.

If you got back your meter, check the ground of the amp plug, to the side of the amp.

Make sure that even if you see the ground lug there, that it is attached to the amp.

You really don't want to AC ground lift an amp. Your finding out why not.

When your hitting the ground lift on that one amp that you own, your are signal ground lifting. Not AC. But, the signal ground is what is carrying the AC to the rest of the system.

If you meter the ground lug, and it is OK. You may need to send that amp in for repair. This could be a number of different issues that are causing your problem.

Kaos is only a form of insanity
Member
Since: Feb 03, 2005


May 29, 2008 10:40 pm

Problem resolved............ It was a faulty earth pin on the multi block feeding the amp. Changed it over and no more sparks are flying

Thanks guys for all your help and input I'll buy you all a beer when i'm over next time ....

The Czar of BS
Member
Since: Dec 31, 2007


May 30, 2008 12:15 am

Glad to hear that you solved the problem.

So... when are you coming over to the states again?

I'm thirsty.

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