ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
VDE 0100 to introduce AFCIs
by LongRunner. 01/17/18 10:32 AM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
Air Compressor feeder conductor sizing
by Potseal. 01/15/18 09:08 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 14 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
noisy music system #23667
03/24/03 07:31 PM
03/24/03 07:31 PM
bill woods  Offline OP
Joined: Nov 2001
Posts: 45
i had a question from a customer today that i couldn't answer. what would cause a loud static popping noise on the speakers of a sound system every time a clothes dryer door opens and closes? i'm at a total loss. anyone have an answer for this?

Work Gear for Electricians and the Trades
Re: noisy music system #23668
03/25/03 10:07 AM
03/25/03 10:07 AM
SvenNYC  Offline
Joined: Aug 2002
Posts: 1,691
New York City
The dryer door pushes a small safety switch inside the cabinet (to start and stop the drum).

The switch is probably arcing and its electromagnetic pulse gets transmitted over the air (picture a spark gap transmitter and a crystal set).

This is more noticeable when you're listening to an AM radio and someone -- even in the next apartment -- switches on a gas stove with electronic ignition "tick tick tick tick"

Just electrical interference, I guess. A quick solution might be to move the stereo away from where the dryer is and plug it into a different circuit.

They might want to change that dryer switch could be reaching the end of its useful life.

Just a thought.

Re: noisy music system #23669
03/25/03 10:13 AM
03/25/03 10:13 AM
sparky66wv  Offline
Joined: Nov 2000
Posts: 2,236
West Virginia
Sven, sounds good to me!

(Did you receive the old switch from me yet?)


Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Re: noisy music system #23670
03/25/03 10:55 AM
03/25/03 10:55 AM
SvenNYC  Offline
Joined: Aug 2002
Posts: 1,691
New York City
Hi Virgil,

Yesss! I DID!! Thanks! Got it this past Saturday [Linked Image] [Linked Image]

Weird looking thing, I didn't realize it was made out of ceramic - first time I've ever seen something like that (all the switches I've ever seen had plastic housings -- even the old ones).

I didn't email you but I wrote you a normal letter back instead - put it in the Post on Monday night.

Re: noisy music system #23671
03/25/03 05:46 PM
03/25/03 05:46 PM
Scott35  Offline

Broom Pusher and
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
Just an FYI,
If you can "bypass" the switch with a ceramic Capacitor, that would suppress the surge responsible for the "Pop".

Bypassing the switch means to connect a Capacitor in parallel with the switch.

Would need a cap that was able to tolerate the heat of the dryer.

Check the "Electrical Theory Area" later on, and I'll post some simple figures for this situation in there.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: noisy music system #23672
03/25/03 07:29 PM
03/25/03 07:29 PM
NJwirenut  Offline
Joined: Sep 2001
Posts: 806
Bergen County, NJ
If you are going to attempt a bypass capacitor installation, be SURE to use only AC line rated ceramic caps, with the proper UL classification markings. The AC line is subject to high voltage spikes, and the cap's dielectric needs to be able to withstand these, and if they DO fail, not to do so explosively.

I might consider doing something like this on my own appliance, but unless you are experienced in and insured for appliance repair, the potential liability issues would keep me from doing any internal "design modifications" on someone's dryer...

Re: noisy music system #23673
03/27/03 03:39 AM
03/27/03 03:39 AM
luciuskwok  Offline
Junior Member
Joined: Dec 2002
Posts: 3
Philadelphia, PA
EMI can usually be reduced by using quality shielded cables and connectors on the sound system, including the speaker wires. The audio cables act like antennae, picking up radio noise from other appliances, local radio stations, etc.

Re: noisy music system #23674
03/27/03 03:46 AM
03/27/03 03:46 AM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I would look to see if any of the audio cables are running close and or parallel to the dryer branch circuit.

Bob Badger
Construction & Maintenance Electrician
Re: noisy music system #23675
03/27/03 04:56 PM
03/27/03 04:56 PM
pauluk  Offline
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Just one point to add:

When fitting a noise-suppression capacitor across switch contacts, it's a good idea to include a small resistor in series, otherwise the contacts closing directly across the capacitor can result in excessive arcing.

Typical values are about 0.05 to 0.1uF with a series resistance of 50 to 100 ohmns.

It's possible to buy a "snubber network" which has the RC combination fitted into a single package for direct connection across the switch. Such devices will be suitably rated for 120 or 240V AC,

Re: noisy music system #23676
03/27/03 07:16 PM
03/27/03 07:16 PM
Bjarney  Offline
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ... page 25 discusses snubber-component selection.


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Brick, NJ USA
Posts: 6,917
Joined: April 2002
Show All Member Profiles 
Top Posters(30 Days)
sparky 20
Admin 20
Potseal 13
Popular Topics(Views)
243,537 Are you busy
180,340 Re: Forum
170,829 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.032s Queries: 14 (0.005s) Memory: 1.0099 MB (Peak: 1.1853 MB) Zlib enabled. Server Time: 2018-01-18 16:01:27 UTC