Strange Electrical Phenominom

[jayenram]

Those two tests would seem to rule out the receiver. Do you perhaps have an active amp located in your speaker system by chance that might be able to mute (looks like you might from photo)?

There's an amplifier in the subwoofer on the bottom shelf below the TV.

If all equipment was not on the UPS test try that again.

All equipment was on the UPS test.

Then ground on everything (perhaps the preamp in the disc player is muting)?

That might be not as easy as it sounds. The subwoofer has no exposed metal chassis. I'll look into it further.

If you tune FM on receiver do you still have the same problem? If not it would indicate receiver (and anything down stream) is not the problem. If it does still happen the problem must be after the receiver (which I assume only leaves the speakers and any amp they contain (or a large power amp if you have that).

I'll need to connect up some form of FM ariel. There is no large power amp in the system.

[lopburi3]

A metal clothes hanger make a good antenna. Can you remove the sub woofer from the system by chance (or is that amp just to subwoofer and not attached in any way to normal system speakers)?

[chownah]

Jayenram,

Do you have lights with two way switches? By this I mean do you have lights that can be turned on and off from two different switches at two different locations?...like at the head and foot of some stairs.

Chownah

[jayenram]

A metal clothes hanger make a good antenna. Can you remove the sub woofer from the system by chance (or is that amp just to subwoofer and not attached in any way to normal system speakers)?

Yes, I can remove it from the system by unplugging it from the mains and the receiver. The subwoofer also has an on/off switch. I haven't isolated from the system up to now but I've tried the tests with it both switched on and off.

[jayenram]

Jayenram,

Do you have lights with two way switches? By this I mean do you have lights that can be turned on and off from two different switches at two different locations?...like at the head and foot of some stairs.

Chownah

I have two lights with two-way switches. Both flourescents. These two do not appear to affect the system any more or less than the one way flourescents.

[Tywais]

Since you said you have fully isolated the system from the AC line using a UPS in battery mode then it would appear to be RF noise generated from the switching of the appliances. Both the fans and the ballast are inductive devices and as such generate RF noise on both turn-on and turn-off.

Does the AV receiver have a tuner built into it? If so, short the antennae input with a short piece of wire. If the receiver is separate, then disconnect it from the AV receiver and try again. Is your remote control infrared? Unlikely it will be a RF transmitter but need to cover all bases. Also want to verify that your speakers are not wireless (RF) but standard wired speakers.

[jayenram]

Does the AV receiver have a tuner built into it? If so, short the antennae input with a short piece of wire.

Yes. Although I do not currently have an antennae connected to it. Neither do I use the receiver.

Is your remote control infrared? Unlikely it will be a RF transmitter but need to cover all bases.

Yes. Remote for both receiver and DVD player are infrared.

Also want to verify that your speakers are not wireless (RF) but standard wired speakers.

All speakers with the exception of the subwoofer (coaxial) are connected by what i would estimate to be 2.5 mm twin copper cables. The cables are denoted as "12 gauge" on the insulation..

[lopburi3]

As the ground (Faraday cage effect) did not seem to help on the receiver believe the next logical candidate would be the disc player. I can't imagine how the fan would cause IR problem so believe we are back to the electric spark type problem the most likely cause but usually a metal case like you seem to have on your equipment would offer good protection from this if grounded (and actually grounding one should have grounded all when interconnected with RCA cables). Starting to look more like ghosts.

[chownah]

I'm just bumping this topic back up because I'm still interested in what happens.

[jayenram]

I'm just bumping this topic back up because I'm still interested in what happens.

I've concluded, rightly or wrongly, that the amplifier has a device built in to protect the speakers from RF generated noise. If I am correct, the said device has a definitive purpose and I shouldn't really be attempting to 'by-pass' it.

However, it took me almost two years to teach the FG to turn lights off when she leaves a room. I don't think I have the patience to now try and teach her to leave them on.

My sparky mate is due here in just over a month. I'll get him on the job.

Thanks for all your help/advice.

[Pink Mist]

Lets get some terminology happening here, what is RF noise and how does that compare to inductive kick when a coil loses power?

[Chang_paarp]

Lets get some terminology happening here, what is RF noise and how does that compare to inductive kick when a coil loses power?

RF noise =radio frequency noise

Inductive kick is the "spike" created when the magnetic field around the coil collapses when the power goes away.

[Tywais]

A ballast stores magnetic energy and when the switch is turned off, the inductive kick causes a momentary high voltage to appear across the switch. This causes it to arc at the moment of switch-off. Arcs are potent sources of broadband RF energy which propagate throughout the room (or whole house) wiring and through the air (RF emission).

This high-frequency energy is coupled through the power line connections (more so with 3-prong power cords) to the chassis of each piece of equipment. When this burst of RF circulates between pieces of equipment via audio interconnect cables, it induces a small burst of RF voltage into the signal path. Audio equipment most frequently responds to such bursts of RF by demodulating it (much like a crystal set) which produces a "pop" or "click" in the audio. In this case perhaps the RF (air borne) is being induced into the audio cables of the system and instead of hearing a pop it is muting the sound.

Still seems strange that the system is sensitive enough to pick up the radiated RF. One test you might try is to get a battery operated AM radio and tune it into the low end of the band with no active station and place it near the light switch. If you turn the light on and off, see if you can hear it in the radio - this will verify that there is radiated (RF) noise. Also do the test with radio near the system.