Axiom Home Page Forums General Discussion Technical Questions 60 hz ground loop - HELP!

Hey all,

It's been a while since I've posted around here. I've been really busy with a trial that lasted a couple of weeks. Interesting case. We were able to squeeze about as much blood from the stone as we could - and ended up settling the case for a fair sum.

Anyway - on to the problems that I've been having.

So far, the AXIOMS have been pretty unbelievable. (I'm still meaning to post some pics). They're clear, powerful and enveloping, with a really great sound stage. I started getting a loud hum in my surroudn speakers about three weeks ago. this started right after I spliced the cable into a second bedroom (which ran from the line going into the main TV room).

I believe that the hum is caused by the cable (cause it stops when I unhook the cable from the wall....). I now have two options: Unhook the cable that I have spliced, and try to run a different line from somewhere else (sort of a huge pain in the @ss). Or, I could get a ground breaker/isolation transformer similar to this.

Does anybody have any experience with these devices (i.e. do they help to eliminate ground hum? and if so, do they eliminate them entirely etc.?) Also, I have seen soem "fancier" ones on eBay and elsewhere selling for $50. Are these different than the one shown, and will it do more than this one? They appear to be very similar to the casual observer.

Any help you can give would be awesome. And, as always, and suggestions from "outside the box" are welcome, b/c God knows, I'm bound to miss things.

Thanks in advance. (Oh, and welcome back Bren)

How did you know I'd be first to jump on a ground loop?

The fastest and easiest way to check your problem and whether an isolation xformer will help is take a pair of 75-300ohm transformers (those things we all have a million of from old VCRs - female F-connector on one side, spade connectors on the other for hooking up coax to an old TV's VHF screw terminals) and hook up the spades to each other (solder them, use bolts or just electrical tape for the time being - don't let them touch each other - that goes without saying, right?)... screw in your cables at each end and see if it helps... it does the same thing as the little Dayton thingamawhiz there.

If it works, either use it, or buy the part you were looking at.

That's the band-aid solution... the real question should be "what did I do wrong to cause this?"... when you say you spliced into a cable for another room - you mean of course you used an unpowered splitter, you didn't actually SPLICE a piece of coax, right? Bunch of other questions - your cable has a grounding block on it at some point (as it comes into the house) right? The ground wire is at least 14ga. as well right? (that's code - so it doesn't burn off before tripping a breaker just in case you end up sending mains AC into it - no frying the cable guy now!)...

Sometimes a ground isolation/ground break is necessary, but better to fix the problem (if possible) first.

Bren R.

Although I have no experience with that Dayton isolator, I'm sure it would work just fine.
I had a 60hz hum im my last place, and all I did to get rid of it was purchase two little transformers from Radio Shack, parts #15-1253 and #15-1140, connect them together, and bam, no more hum. Total cost was about $10 cdn.
Spending $50 seems a little rediculous to me, but maybe those ones eliminate other types of interference and hum as well.

Bren and Craig - Thanks. Bren - your "easy" solution sounds "not so easy" to me...and yes, I used a non-powered splitter from outside the home.

Craig - I'm gonna check out the rat-shack stuff right now.

thanks.

I was referring to just putting two 15-1140s (thanks to Craig for the RatShack part #s) back to back... if you're just going to buy them, Craig's idea is easier... screw the spades to the terminals... but if you already have two 75-300 matching xformers and don't want to buy the 15-1253 (which looks like something from Super Mario Bros. to me)... just hook up spade to spade.

Difference between the two parts he listed is one has screw terminals, one has spades, they do the same thing.

Do you ground your grounding block to a cold water pipe? To a grounding rod? Have you tried grounding the splitter itself?

Bren R.

Bren,

I now understand your comment above, after looking at the parts and re-reading your suggestions. (Just a little slow in this department sometimes).

As far as grounding stuff myself - the simple answer is either "no" or "i don't know". I live on the top floor of an old row-house. The cable comes into my house off of the flat rook of the building. I went up onto the roof and split the signal (at the place where the cable guy originally split the cable to run it from the back of the house to the front). I wouldn't even know where to ground the signal to a copper pipe (i.e., where any pipes are, etc.).

I'm gonna try the band-aid solution first. In truth, the hum is annoying to me, but I can live with it. (for now, I just unplug the cable when I'm not using it). But, I'd like to avoid that. I'll let you know how the rat-shack parts work out.

Someone beat me to it I guess. I was typing my post while Bren posted his, and we basically said the same thing. The two parts I suggested is just a dead simple way of fixing the problem, which I read about on the internet somewhere else. It eliminated all my hum, hopefully it will help you too.

Sadly I respond in here very slowly...

I have messaging A.D.H.D., I'll wander off, surf for a while, check my email, respond to it... do some work, remember the open message and finish it up.

Bren R.

In reply to:

---

I went up onto the roof and split the signal (at the place where the cable guy originally split the cable to run it from the back of the house to the front). I wouldn't even know where to ground the signal to a copper pipe (i.e., where any pipes are, etc.).

---

Did you see a smaller gauge (thickness), piece of regular old wire going from a screw on the cable company's splitter to anything else metal on your house? Is there a screw on that splitter with no wire going to it? (It might be labelled "Gnd" or "ground", or it might have a little line drawing of an upside down triangle near it.)

I know that in Maryland, the cable company MUST ground the cable at the first junction on, or inside of the house. Sometimes, they use a 1 to 1 splitter (one in, and one out) with a grounding screw to accomplish that. Place a service call and tell them that you noticed that the incoming cable has no ground connection. They will send someone out to fix it. Free. If they don't, mention that you are a lawyer... Uh... I guess you already know that...

THanks guys. I still haven't had a chance to plug in the parts yet, but hopefully it'll work. in the event that it doesn't work, I'll call up the ol' cable company and see what they can do.