Buzzing noise question for RG

[KMS]

This is probably a question best suited for RG but maybe someone else has had this problem before and knows what the problem was.

Recently I had some hum problems that seemed to be coming from my guitar pickups where RG gave me some advice about my house wiring that led to the discovery of a dangerous wiring problem in my house, which I fixed and probably worried the heck of RG while I was doing it..... But the hum is gone and my family sleeps safer now that it is resolved.  Thanks RG.

Now I have another problem but it not at my house...it is at our practice studio.

About two weeks ago I started getting a "Buzz" sound at the studio but only when I use my router...which includes..(in chain order starting at the input)....the OS from GGG....tonepad's Callgate.....GEO A/B/Y (1999 version) split 6 ways.....BOSS OD on one of the 6 splits....tonepad's tremulus lune on another of the splits......535 Crybaby on another of the splits....3 remaining splits are clean.....then into a  stereo TL072 based simple volume mixer and then the output.  The A/B/Y switching is set up in the mixer.  The GEO A/B/Y and the mixer are 9VDC bipolar. Everything else is regular 9VDC.

It is buzzing at the studio....but only at the studio, and there is no buzzing if I run my signal straight into the amp and by pass my router.

My Bass player also noticed around the same time at our studio that he is getting shocked on the mic when his fingers are on the guitar strings.....I tested it out with my guitar plugged into his amp and I got shocked too.

Last week I got shocked by my router Casing at the studio (first time that ever happened).

So...I brought everything home to my house and plugged it into my correctly wired house wiring and no problems whatsoever.  In fact...our system (several amps and all kinds of other electronic paraphernalia) all sounds in general much quieter at my house.

So...RG.....is this another loose neutral wire problem at our studio?

Could be insufficient amp supply? We draw about 10 to 12 amps (I think).

The studio is at a very old house...with fuses in the service box. The ground from the service mast looks to be #6 solid copper hooked to a rusted iron rod for the earth ground. We have a brand new 150ft #12 extension chord from the house to the metal shed where our studio is at. The shed is wired with new 3wire #12. The service triplex has a copper neutral. I can't tell what type of wire comes from the service mast to the service box. The distribution wires inside the house are #14 copper two wire.

Here are the things that I know about power consumption at the studio; 250 watts of lights, 200 watt input Kustom (100 watt output), 900watt input Peavey Power mixer (450watt outputt), 2 amps worth of wall wart stuff, 45 watt input Peavey amp (15watt output), and 45 watt input Marshal amp (15watt output).

And the things I don't know the input for at the studio; 1 computer and monitor, 75 watt output Peavey amp, 100 watt output Peavey amp, DP 50 Techniques drum machine, rack mount analog delay, and a medium size house fan.

Can I calc amps from the watts?  How?

There is also a refrigerator in the house on the same distribution circuit, but the service box has several distribution circuits split from 4 main 30 amp fuses...there are two 30 amps fuses on each of the hot wires from the transformer. Our distribution circuit is also run by the same fuse for one of phases of the 220V well pump motor. There could be other items powered by the same two 30 amp fuses, and there is no way to tell with out turning everything on and shutting down one fuse at a time.

From the service box to the receptacle where we plug into with the #12 extension cord is about 40 ft of # 14 two wire.

Thanks in advance,

[R.G.]

You already know the answer.

I don't know that it's the neutral that's a problem, but it's the wiring in some way. I would not practice there again until the wiring gets fixed. Something is leaking current and it's not getting pulled to safety ground. Could be an amp, could be a board, or your router - or a light switch or bum wiring. Could be an old rusty fuse or a corroded contact in the fuse box. Could be a combination of high ground impedance and the rest of that, too. The 150 feet of extension cord isn't helping with any of that.

Buzz noises are usually associated with electrical impulses. Fluorescent fixtures and lamp dimmers are notorious, but any arcing contact can cause the same kind of noise.

I'm glad your house got fixed. It's always a guess when we do long distance debugging, and it's good to hear back that one of them worked out. 

[KMS]

I know the answer is going to be a lot of testing.....maybe...

Your suggestions are the first things I will consider... Last time I did a lot testing at my house and after I ran out of ideas you suggested aluminum wire as a potential problem and sure enough that is exactly what it was.

I am a little smarter this time around......but the answer might not be the same.  Rusty fuses.................................OK......I think this gives me an idea...because that old fuse box is rusted badly.  Bum wiring is also possible but will not be easy to check ( I had thought of that).  I hope it is not an amp....but that is something I had not considered.  I will just have to unplug everything and start test each item one at a time starting with the fuses. Then move to the bum wireing issue next.

Nothing I can do about the long extension cord....I have electrical dope on the plug ends and bought new #12.

My router works prefect at my house and I only get shocked by it when it is plugged into the amps at the studio. The shock is mild....but I know it means danger concerning something.

We will cease practice at the studio until this is resolved....that is good advise we can use right now...no doubt.

Thanks RG for you ideas...and I'll post the results as it becomes available.

[R.G.]

Good - be safe!

The thing about long ground leads is that they make any leakage from any of your equipment more noticeable.

Here's an interesting test you might want to try. Drive a metal rod into the ground at the shed, and measure the voltage difference between the ground rod and the safety ground on the end of your extension cord. If the wiring back at the house is OK, that should be almost nil. If the wiring at the house is bad, there are ways it could be bad and you won't know, but if it's wildly off, there is definitely a wiring problem at the house.

Now plug in an amp and play - but measure the safety ground to real metal rod ground again. If it's tiny, OK. Try another piece of equipment. That will let you sort out if there's only one piece of equipment that's leaky. IF any amps are two wire, measure signal ground to metal rod ground. You can also plug up the equipment and measure the voltages between signal grounds on different equipment. That is, after all how you're getting shocked. One or more of them has a voltage higher than the others, or you couldn't get shocked.

I ran a 250 foot length of 8/3  direct burial underground feeder wire from my main box to some pumps down at the rainwater tanks. It was a pain to dig the trench, but it works the pumps well, and I have less than 50mV of ground difference between local dirt ground and the cable safety ground.

[KMS]

OK...ground rod (anode) is installed at the shed and we hooked the earth-ground-wire to the third prong of the receptacle since the shed is wired with 3 wire (even though the house is not 3 wire).

It just made it easier to test all the stuff in the shed having the test between the 3rd prong and the neutral prong.

With nothing pulling a load at the shed and at the very end of the circuit (ground rod is 10ft from the test) I got 1.0 VAC between the neutral and the earth ground.

As I plugged in and turned on each piece of electronic equipment the voltage between earth-ground and neutral slowly increased up to about 3VAC with everything plugged in.  I operated all the polarity switches on the amps and it made no difference.

There did not seem to be any one item that contributed to a majority of the voltage increase between earth-ground and neutral.

3VAC.......now what?      Can I just hook the newly installed earth ground to the neutral at the shed and make sure we unplug the shed when we leave?

[R.G.]

I was actually hoping that you'd find that  one amplifier was doing most of the leakage, and that one could get fixed. That's not it.

But now I'm scared.  You say the HOUSE IS NOT WIRED FOR THIRD WIRE SAFETY GROUND?? AGGGGHHHH!!

If the house is not three wire, it doesn't do a thing for you to have a three wire extension cord. The third wire not being tied to the house's safety ground means that the third wire in the extension cord is purely decorative.

The results you measured are not inconsistent with what you tell me. The resistance of all the copper wire from the neutral at the shed back to the power pole where neutral is presumably grounded contributes to that 3Vac. I suspect that if any large loads inside the house are turned on, the 3Vac goes up as well. More drop in the current carrying lines.

The problem with simply grounding the third wire in the shed is that if there is any fault in the house, that extension cord is going to carry the fault current, not the lines going back to the pole. And I'm not sure what happens from there, but I have this itchy feeling that it's not good. Smoke, fire, electrocution, plague, pestilence, nuclear ware, the end of the universe as we know it, or worse...

There is one way I could see that would make it safe enough for me to use the electricity in that setup. And that is to install an isolation transformer big enough to handle the whole load out in the shed, then safety ground the secondary of that isolator. That way you're not providing a path for fault currents from the house, or contributing to the house catching on fire any more than it already is. But an isolator that big would weigh 50 pounds easily and is not a cheap item unless you hit it lucky at a surplus house.

You realize that I'm being extra cautious here. Not seeing the actual setup limits what I can guess. But this is one to play safe with, not to just stick a ground rod in out in the shed.

This is not a junior-electrician problem. It's somebody else's house (as I remember from earlier notes). It's certainly not safe IMHO. You can't fix the house, and fixes in the shed are dangerous. Advise the house owner of the issue, and that a competent electrician ought to look at it. That won't help, because the right answer is to rewire the house and that's big bucks.

The only good advice I can give you here is - don't. I personally would not practice there, and would advise my friends not to either.

[KMS]

I appreciate your advice and you saved me a lot time de-bugging the problem......it was the obvious problem once again.

The transformer idea I had not thought of.....but I expect we will find a new place to practice.

I will inform the home owner of the issue.


FYI....I moved all the equipment to my house and made the same test in my garage (installed an anode too) and I measured 0.5VAC with no load in the garage except a fluorescent bulb and the AC and refrigerator were on in the house. The same scenario took place as I hooked up each piece of electronic equipment except the voltage was much less......0.8VAC between neutral and earth ground at my garage with everything pulling a load (the garage is wired with 14-3) and is 70ft from the service box.

I would assume that if the garage was wired with 12-3 I would hardly measure any voltage.

Thanks RG.

[R.G.]

Power line wiring is always tricky because the impedances are so low and the currents so large. That and the fact that you're always standing on dirt - a live conductor in most cases.

It's reassuring that you found the line-to-dirt voltage much lower in your garage. It's a comforting confirmation of the guess.

One thing that is a really good thing to have for any gigging and practicing band is one or two of those three prong plug-in outlet testers. They tell you at a glance whether the outlet is wired correctly and safe to use.

Good call on changing practicing locations. Rock and roll is an obsession, but it's not worth dying for.

[A.S.P.]

sounds like a 3rd-world problem...

[R.G.]

It is very like a third world problem - or any place where the electrical utilities are not the very latest and regularly updated. The USA changed over from two wire to three wire AC starting back in the middle of the last century, and there are still places where there are only two-wire houses.

[markm]

It is very like a third world problem - or any place where the electrical utilities are not the very latest and regularly updated. The USA changed over from two wire to three wire AC starting back in the middle of the last century, and there are still places where there are only two-wire houses.

There are LOADS of two-wire houses in my area.
Worst part was a club that I used to play at.....
nothing but buzzzzzzzz

[Fret Wire]

The USA changed over from two wire to three wire AC starting back in the middle of the last century, and there are still places where there are only two-wire houses.

I've seen many used amps that came out in the 80's that have had their ground prong snipped off. Pretty sad, huh? Says a lot about building code enforcement and the monitary value people place on their safety.

[markm]

The USA changed over from two wire to three wire AC starting back in the middle of the last century, and there are still places where there are only two-wire houses.

I've seen many used amps that came out in the 80's that have had their ground prong snipped off. Pretty sad, huh? Says a lot about building code enforcement and the monitary value people place on their safety.