Stubborn Home Audio System Hum Problem

[TLS Guy]

No problem about the comment, I have an electrician calling me in the morning. This company does "Lightning Certifications", I suppose the insurance companies require that after a claim, at least in my area.

We'll see when he can come and what he finds. I really think things are ok, it's been 12 days now and I don't detect anything wrong now other than the remaining issue with the amp. We'll see if I am right or wrong.

I'll keep you informed.

Yes, but that is very telling. You did not have the hum before the lightning strike, and now you have hum that is cured by totally isolating your system from the electric system in your house. That has to indicate a high probability of a serious problem.

 

[bergwayne]

Here's the latest. The company I first called to inspect my house electrical system was supposed to get back to me today but never called.

I started calling around and was recommended to a guy with his own Electrical Inspection business who was an electrical inspector for 30 years for the State. I talked with him and explained my amp problem as well as all the other issues. He said he wasn't going to be great help on audio equipment but could go through my electric service panels and check whether there appeared to be any damage. He said he could go through each circuit but didn't think it was necessary to start doing that level of check unless problems were showing up. He said it would be about a two hour service call to give it a go over, more if he started finding problems.

I feel comfortable with this, I know it isn't the 100% full blown check but if anything is found I will go that direction.

What do you think? Not likely to find the hum problem but good enough to make sure the house doesn't burn to the ground? It's been about 14 days now, no new problems have been found.

 

[TLS Guy]

Here's the latest. The company I first called to inspect my house electrical system was supposed to get back to me today but never called.

I started calling around and was recommended to a guy with his own Electrical Inspection business who was an electrical inspector for 30 years for the State. I talked with him and explained my amp problem as well as all the other issues. He said he wasn't going to be great help on audio equipment but could go through my electric service panels and check whether there appeared to be any damage. He said he could go through each circuit but didn't think it was necessary to start doing that level of check unless problems were showing up. He said it would be about a two hour service call to give it a go over, more if he started finding problems.

I feel comfortable with this, I know it isn't the 100% full blown check but if anything is found I will go that direction.

What do you think? Not likely to find the hum problem but good enough to make sure the house doesn't burn to the ground? It's been about 14 days now, no new problems have been found.

Make sure he fully checks all grounds and neutrals. If you send all your key pads and amp for service and they find nothing wrong then you have a big expense. I feel there has to be some grounds that have excess resistance as a result of the strike.

He needs to check your main ground and make sure it is up to code. He needs to make sure there is no excess neutral resistance at the panel.

The resistance of all grounds involved in your sound system need checking carefully, as well as the neutrals. The grounds to the receptacle boxes of all control devices, such as your key pads need checking carefully, as well as the grounds from your amp to the key pad.

Explain to the electrician, that it is resistance between grounds, that is always the cause of ground loops and hum. So he needs to be looking very carefully for increased resistance in grounds as a result of the strike.

 

[highfigh]

Here's the latest. The company I first called to inspect my house electrical system was supposed to get back to me today but never called.

I started calling around and was recommended to a guy with his own Electrical Inspection business who was an electrical inspector for 30 years for the State. I talked with him and explained my amp problem as well as all the other issues. He said he wasn't going to be great help on audio equipment but could go through my electric service panels and check whether there appeared to be any damage. He said he could go through each circuit but didn't think it was necessary to start doing that level of check unless problems were showing up. He said it would be about a two hour service call to give it a go over, more if he started finding problems.

I feel comfortable with this, I know it isn't the 100% full blown check but if anything is found I will go that direction.

What do you think? Not likely to find the hum problem but good enough to make sure the house doesn't burn to the ground? It's been about 14 days now, no new problems have been found.

Go out and look at the power company's cable splices where the service connects to the cables going to the meter box. If they look like big butt connectors (about 3"-4" long and about 3/4" diameter) and they have been untouched for ten years or more, call the power company and have them inspect their feed, preferably also replacing the splices. These dry out over time and with a lightning strike, I can see how they would fail. They don't use that kind much now and it's because the new type is more reliable. If your neutral is intermittent (the bare third cable), you can have lots of problems, including motors, light bulbs and other equipment failing prematurely and often.

 

[TLS Guy]

Go out and look at the power company's cable splices where the service connects to the cables going to the meter box. If they look like big butt connectors (about 3"-4" long and about 3/4" diameter) and they have been untouched for ten years or more, call the power company and have them inspect their feed, preferably also replacing the splices. These dry out over time and with a lightning strike, I can see how they would fail. They don't use that kind much now and it's because the new type is more reliable. If your neutral is intermittent (the bare third cable), you can have lots of problems, including motors, light bulbs and other equipment failing prematurely and often.

You make a good point the problem may not be in the house. I was asked about a situation by the local artisans about a house on the other side of the lake that was having repeated electrical problems, including repetitive burning out of the well pump motors. The problem cam to light in the winter, and I think was precipitated by increased electrical heating loads. However there had been damage from a lightning strike to that residence in the summer, which I think was the cause.

It was the neutral from the panel, but you could not tell by looking at it.

I had a situation where the voltage was on the low end of normal, and quite often below, causing my UPS units to support voltage. I was also getting excess failures of a Direct TV box downstairs and the roof amps. That unit was not on a UPS then. I checked the AC waveform with my scope, and it had severe crossover and hysteresis distortion. I measured the distortion and it was 23%! The maximum allowable id 5%. I insisted the power company get my service to spec. The transformer serving this house had gone bad, possibly lightning strikes at some time or age. The transformer was replaced, and end of problem

I'm not certain the OP has the right individual. Inspection is not going to cut it. Careful testing and measurement is required here, just looking is not going to cut it.

 

[bergwayne]

Go out and look at the power company's cable splices where the service connects to the cables going to the meter box. If they look like big butt connectors (about 3"-4" long and about 3/4" diameter) and they have been untouched for ten years or more, call the power company and have them inspect their feed, preferably also replacing the splices. These dry out over time and with a lightning strike, I can see how they would fail. They don't use that kind much now and it's because the new type is more reliable. If your neutral is intermittent (the bare third cable), you can have lots of problems, including motors, light bulbs and other equipment failing prematurely and often.

My service is all underground. There is a transformer on the block and all the houses feed underground from it. My house is about 4 years old but the service out by the street has probably been there 10 years. I don't think I can do what you suggested as far as looking at splices.

I'll see what the inspector says today. If the has any indication there might be a problem I'll call the Power company.

 

[bergwayne]

I'm not certain the OP has the right individual. Inspection is not going to cut it. Careful testing and measurement is required here, just looking is not going to cut it.

I agree he is probably not the ideal person but if he spends two hours checking things and finds nothing wrong, I'm going to feel pretty good about it. If he finds anything, then I think it's time to get the full blown check that Rich was talking about. He said he will be checking for continuity, if I remember right, I'm not 100% sure what that means.

I should know something by this evening, the guy is coming in about an hour. I think he should be comparable to calling in an experienced electrican but agree he's not really the "lightning" expert. I'm not going to push the amp solution on him too hard because I'm pretty sure audio electronic issues are out of his league. I just want him to look for damage to the house power system, checking the grounds and neutrals and such. I'm trying to avoid the house burning down right now.

Hopefully, what I am doing is reasonable. It might not be the last step.

 

[bergwayne]

The latest, the electrical inspector came today. I walked him through the things that blew out and where they were connected.

He went through my main service and two subpanels. I would say it was more of an inspection with a flashlight than much testing. He said the panels looked like they were new and they was no evidence of flashes or burns. He only spent about an hour because he didn't feel it justified more time. He said the original electrical work was well done. He checked my main ground, it is actually in two places, the copper water line and a rod buried under the main service grounded box.

I showed him the hum and he agreed it was pretty loud. He called an electrical engineer he works with to see if there was an explanation for why it hums on the regular service but not on the invertor. As I understood it the electrical engineer said there is a difference between the two types of power. The house service was a smoother wave on a scope and a problem in the amp could be amplified. He said the invertor produces a "jerkier" wave....

 

[TLS Guy]

The latest, the electrical inspector came today. I walked him through the things that blew out and where they were connected.

He went through my main service and two subpanels. I would say it was more of an inspection with a flashlight than much testing. He said the panels looked like they were new and they was no evidence of flashes or burns. He only spent about an hour because he didn't feel it justified more time. He said the original electrical work was well done. He checked my main ground, it is actually in two places, the copper water line and a rod buried under the main service grounded box.

I showed him the hum and he agreed it was pretty loud. He called an electrical engineer he works with to see if there was an explanation for why it hums on the regular service but not on the invertor. As I understood it the electrical engineer said there is a difference between the two types of power. The house service was a smoother wave on a scope and a problem in the amp could be amplified. He said the invertor produces a "jerkier" wave....

BS! The inverter completely isolates your amp from the home electrical supply! The inverter wave for is not necessarily jagged, it could well be better than the house supply and probably is.

You will have to get back the original installer of your system, who felt the problem was with the house electrical system. He is probably right, but get him back to prove it.

This is as far as any one can go without being in your home with equipment. So I have no further advice for you, but obviously remains a fault in your house electrical system, your sound system or both.

 

[bergwayne]

cont'd....which might be masking whatever is causing the hum. I know that's a crude explanation but it sounded about like what TLS sugggested earlier. The engineer said he would bet the amp has a blown capacitor or something near the power supply where the part probably cost 25 cents but will cost $400 to repair.

He then called a guy that he knows that just deals in circuit breakers and he told him I had electronics blown out all over the house from a nearby lightning strike. That guy said a surge of the type I must of had would produce almost no long term probablity of having faulty circuit breakers in the future.

I paid him and he was off, I'm not as concerned about my house burning down now. He said I could add a whole house surge protector for about $500 if I was interested, it would require another subpanel. He said they are not reliable if there is a direct hit.

Now back to the amp, I think it's time to send it in. I'll follow-up when I get the results of that. I suppose that will be awhile.

 

[bergwayne]

Thanks to everyone for trying to help with my hum problem. I just got the unit back from Russound (it took me awhile to get it packaged and sent off to them). Russound said the lightning did something to the connections near the power supply. They did a repair, I'm not sure exactly what it was, they may have replaced the power supply also. I hooked it up again and the hum is gone and the unit works! I'm pretty happy about that.

I realize this doesn't explain why the hum would go away when the amp was connected to an invertor instead of the normal house power. That, remains a mystery forever..............

 

[highfigh]

Thanks to everyone for trying to help with my hum problem. I just got the unit back from Russound (it took me awhile to get it packaged and sent off to them). Russound said the lightning did something to the connections near the power supply. They did a repair, I'm not sure exactly what it was, they may have replaced the power supply also. I hooked it up again and the hum is gone and the unit works! I'm pretty happy about that.

I realize this doesn't explain why the hum would go away when the amp was connected to an invertor instead of the normal house power. That, remains a mystery forever..............

That shouldn't be a mystery- the inverter isolated its power supply from the rest of the house's electrical system.

 

[bergwayne]

But that is the mystery. As it turned out the hum was coming from damage in the amp. Isolating from the house power supply by using an invertor somehow compensated for the damage in the amp eliminating the hum, where the house power did not compensate for the damage in the amp and the hum persisted.

That is at least wierd, if not a complete mystery.