Interesting power problem with NV112

seldomfed · From: Colorado

We had a gig in a hay barn Saturday for a branding party. Anyway...

ran an extension for power from a GFI outlet in the house - used a couple big guage AC power cords. (12)

Plugged everything in - and every time I pluged in my NV112, the GFI popped!

Traced the problem to one of the power extension not wired correctly. AND it was like this from the factory! - not a repaired cable!, so somewhat disturbing since it is used often. We swapped the cable with one wired correctly and everything was fine after that.

So... what is it in the Peavey NV112 that would have cause the ground fault when nothing else did?

Note: that nothing was powered on when I plugged in the NV112 - all equip was off. As soon as I plugged in the NV112 the GFI popped. We tested the amp by taking it to the house and plugging it in - the GFI did not trip, only when routed thru the extension cord. AND no other amp, or PA tripped the GFI thru the bad AC cord ????

Lessons learned -
1) thank goodness we had the wireing tester in the PA kit(little plug that displays correct wiring for AC)
2) test all your cords when you buy them before the first use!

chris

------------------
Chris Kennison
Ft. Collins, Colorado
"Listen Sooner"
www.book-em-danno.com
www.seldomfed.com

John Daugherty · From: Rolla, Missouri, USA

Did the other equipment have 3-wire grounding plugs?

Chick Donner · From: North Ridgeville, OH USA

GFI's (ground fault interrupters, not Gene Field guitars) work by sensing differing amounts of current (like 15 MICRO amps) between EITHER side and ground. So don't do like the idiot showing off to the girls who grabbed the white and black coming out of a GFI outlet . . . it did not shut off the current because the current thru the idiot was the same in both legs.

Lee Baucum · From: McAllen, Texas (Extreme South) The Final Frontier

Here is a small device that is similar to the one I carry in my Pac-A-Seat.

Click Here

"Diagnoses several common wiring faults, including open ground, open neutral, hot-ground reversal and hot-neutral reversal fault conditions (detects most common wiring problems, but not all fault conditions)."

The manufacturer does say not to use it with GFI outlets, though.

seldomfed · From: Colorado

That little plug thingy in your pack-a-seat is what we have too - and it saved the day. So not sure why they say not use for GFI outlets. It worked.

yes, all other equip had 3 prong - but when we plugged in equip thru that bad cord - nothing tripped the circuit except the NV112?

oh well, the cows got branded, the tequilla got drunk, the food got et, and the dance was good - so not much else to worry about.
chris

------------------
Chris Kennison
Ft. Collins, Colorado
"Listen Sooner"
www.book-em-danno.com
www.seldomfed.com

Lee Baucum · From: McAllen, Texas (Extreme South) The Final Frontier

I started carrying that little tester with me after some friends had about $5,000 worth of equipment fried at a newly remodeled club. The club had a new stage, new lights, plenty of outlets around the stage. This was the first band to use the new stage. Everything looked great. It was the unseen wiring problem that fried their equipment. As I recall, the electrician had reversed two of the three wires that went to the stage plugs. After lots of fighting and threats, the club owner finally paid to have the equipment replaced.

Lee

Mike Brown · From: Meridian, Mississippi USA

This reminds me of Rush Limbaugh's "SUV syndrome". It was the SUV's fault, not the operator of the SUV. 'Nuff said.

Jay Fagerlie · From: Lotus, California, USA

Here's my take:
A GFI senses current in the ground to low side of the supply (if it sensed the high side, it would always shut off, no matter what was plugged in)
I assume that Peavey follows the rules for wiring power plugs the way every manufacturer should. (I know they do....)
The reversed connections on the faulty extention cable caused the GFI to trip since the GFI sensed a false current draw between the ground and low side of the AC circuit.
Jay

Edited to add:
Seems to me the Peavey pointed out a problem to you with something else, it behaved exactly as it should have.
J

[This message was edited by Jay Fagerlie on 10 May 2005 at 09:48 AM.]

Mike Brown · From: Meridian, Mississippi USA

It actually protected the user of the product.

Paul Honeycutt · From: Colorado, USA

If the amp has a removable "computer" type cable like so many new electronic devices do, make sure tht the cable is wired correctly. A few years ago a live audio company (QSC or Allen & Heath, I believe) got a shipment of cables that were wired wrong. It didn't blow anything up, but it sure confused a lot of end users.

John Daugherty · From: Rolla, Missouri, USA

Very good point, Paul. The 112 does have a removeable cord. It is possible for it to be replaced with another cord that was wired wrong.

Jack Stoner · From: Kansas City, MO

IBM had that trouble back in the late 80's with some 4224 model printer AC power cables. They had a "recall" and replaced all that came from a specific supplier's (in Mexico) batch. In those the hot and neutral were reversed at one end.

seldomfed · From: Colorado

thanks for all the input...

to quote my orig. question:

Paul Arntson · From: Washington, USA

Mike Brown might be able to shed some light.
From reading Peavey's technotes on power: http://www.peavey.com/support/technotes/safety/shockhazard.cfm
I might guess they have a noise capacitor installed between the neutral and the ground wires.
Under certain circumstances, (like hot and neutral reversed in the extension cord) this would cause a GFI to pop. The cap would pass just enough current to trip the GFI if 120VAC were across it, but not if it were between the neutral and the ground.

A 0.1 uFd cap would pass around 5mA RMS at 120VAC.

[This message was edited by Paul Arntson on 17 May 2005 at 07:16 PM.]

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