ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
nec 110.3 (B)
by gfretwell - 09/22/21 11:11 PM
Grounding electrodes
by gfretwell - 09/07/21 03:41 PM
Looking For Electricians in the Midlands
by Alex247 - 09/06/21 05:26 AM
New in the Gallery:
Now you know.
Now you know.
by Tom_Horne, September 7
February, North East Indiana
February, North East Indiana
by timmp, July 25
Who's Online Now
1 members (Scott35), 40 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Feb 2004
Posts: 115
H
Haligan Offline OP
Member
This conundrum is happening at my own place.

The gas furnace has an electric igniter. When the thermostat triggers it, it makes the rapid sparking noise just like your basic stovetop and other furnace igniters. But, if the stereo is on, the clicking comes out of the speakers.
I checked grounding at both the stereo and furnace.
I moved the stereo to the opposite leg of my service.
I tried two fancy audiophile filters (thankfully money-back guarantee!)

I've run out of ideas apart from an expensive isolation transformer.
What have I missed?

- Eric

Joined: Jul 2004
Posts: 9,663
Likes: 4
G
Member
There is a lot of RF noise coming from any spark lighter like this. It may just be airborne and not coming from anything wired into the set. The first thing you need to do is figure out where it is getting injected into the signal path. I would disconnect the speakers and try a headset with a shielded lead to eliminate the idea it is coming directly into the speakers, although that is unlikely. Does it seem to favor any particular input? You could make up terminator plugs for any unused ones. If not you may just have it being "detected:" by a diode in the amp and I am not sure what you do about that other than better shielding around the amp.
I doubt an isolation transformer will do anything. If this is a fairly new amp, it has an inverter power supply.


Greg Fretwell
Joined: Feb 2004
Posts: 115
H
Haligan Offline OP
Member
Thanks Greg. I did a lot of reading on RF noise. I'm also going to check out replacing the igniter. It's more than 15 years old. Maybe ignition technology has improved.

Joined: Nov 2005
Posts: 826
J
Member
What are the conditions at the stereo? AM, FM, Tape Mon, Aux, Video??? Does the volume setting impact the noise volume?
I would try installing some low pass filtering as close to the igniter as possible.
Joe

Joined: Feb 2004
Posts: 115
H
Haligan Offline OP
Member
The receiver is set to CD or AUX. Noise happens on both.

I haven't been able to run to the volume knob in time, but I listen to different things at different volumes and when I'm blasting something, the noise says the same.

Here's another wrinkle- It doesn't happen every time. One out of 20 times the noise doesn't happen.

I tried a noise filter at the j box closest to the furnace. Maybe I should wire it inline with the igniter. I don't have to worry about a warranty- the furnace is 60 years old.

Joined: Jul 2004
Posts: 9,663
Likes: 4
G
Member
Can you look in and see the igniter? Maybe some aluminum screening, grounded, would act like a faraday cage around that hole and knock it down.


Greg Fretwell
Joined: Jul 2007
Posts: 1,335
S
Member
Have you looked at the service grounding and bonding? What are you listing to through the stereo? Cable radio or FM?


"Live Awesome!" - Kevin Carosa
Joined: Feb 2004
Posts: 115
H
Haligan Offline OP
Member
Service grounding and bonding check out okay. I sunk a rod when I bought the house. The electrode is still on tight.

I'm listening through CD or AUX on the stereo. There's no radio on it. It's just an amp.

Joined: Dec 2002
Posts: 205
G
Member
May be a silly idea, but are both circuits on RCD?
I suffered a similar problem quite a lot of years ago and gave up in frustration trying to solve it, eventually putting it down to my audio system being "home brewed". In my case I couldn't attribute the source to one item.
Eventually I updated my panel to an RCD one, incidentally discovering a neutral earth short half way round my ring main. Doh! It was a neutral wire knicked by the faceplate screw. Once fixed, the audio system problem disappeared.
I believe that the currents circulating between the short and power source behaved like an hearing aid loop system, radiating at low frequency around the house and picked up by the stereo.


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
mxslick
mxslick
Atomic City, ID USA
Posts: 806
Joined: October 2004
Top Posters(30 Days)
timmp 3
Popular Topics(Views)
283,074 Are you busy
216,807 Re: Forum
203,189 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5