I bought some cheap computer speakers to plug into my portable CD player because I don’t have a stereo.
These speakers have a ‘remote control’ that is just a control set on a wire (power, volume, tone). There is an LED in this that was bugging me, so I opened it up and shorted the LED.
Now when the speakers are on, there is a very faint radio signal coming through them, whether or not there is any input. I just got them yesterday, so I don’t know if it has anything to do with the short. I suspect it doesn’t. Does anyone know what causes this and how it could be stopped?
Rather than shorting the leads of the LED, it’s a far better idea to simply cut one of them. In any case, this doesn’t have anythjing to do with hearing the radio station. Chances are there is an amplifier, either battery-powered or AC adaptor-powered, that is rectifying and amplifying a reasonably strong AM station. It’s not at all unheard of, and I’ve seen this happen in speakers, telephones and tape recorders.
Its probably an AM station in the area.
Some how your speakers are detecting the signal.
All that takes is something acting like a diode.
If it didn’t do it with the led just hook it back up and cover it with some tape.Or use your imagination with the coverup.
Also there may be a high powered FM station in the area.Sometimes there is so much spurrious radiation it just overpowers equipment. Contact the stations engineer.
Interestingly there are cases where someone has had teeth filled or braces installed and they would hear music.
Well when I cut a lead to the LED it opened the whole circuit and nothing worked (you can tell this is low quality equipment). It’s very reasonable to think that there’s just an overpowering amount of signal in my area – i’m in downtown Toronto.
Thanks guys! I doubt there’s anything I can do about it.
Wait a minute. The equipment was working fine until you messed with it and you complain it’s bad? Because an LED bothers you? I suspect the problem is not so much with the equipment as you think.
If the LED bothers you that much, replace it with a standard 1N4001 silicon diode, or two in series if the forward voltage drop of one is insufficient (red and green LEDs have a V[sub]F[/sub] of about 2 V typ., and silicon diodes have a V[sub]F[/sub] of about 0.7 V). Frankly, I wouldn’t think it would be worth the effort, but at least this will maintain the electrical integrity if the circuit.
An LED isn’t just a fancy light bulb, it is a diode, which only allows current to flow in one direction. I’d guess that depending on how the circuit containing the LED is wired, bypassing the LED allowed the current induced in the wire by the radio signal to reach the speakers. In this case, the LED filtered noise from the circuit.
Your speaker set is a simple radio: it’s got speakers, an amplifier, and an unshielded piece of wire (could be the audio cable, could be the power cable) ready and willing to serve as an antenna.