I have a door intercom that has a switch to turn one way to “listen” and the other way to “talk”. When the “talk” position is used, it works fine. However, when the “listen” position is used, there is an extremely loud buzzing noise. There is only one door speaker connected to this main inside intercom box. It is a fairly old model, not sure how old. On the inside it says “Rittenhouse Div., Emerson Electric Co. Honeoye Falls, NY. Model M7034. I tried to find some info on the internet, but was not successful. Anyone know what might be causing the buzzing noise and how to get rid of it?
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go to Radio shack and get some "tuner cleaner" spray, try that. Or 'toggle back an forth rapidly a few or more like a bunch of times, y probly have some corrosion or crud in the contacts.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Sounds like in the listen mode the amp is picking up noise from possibly a lamp dimmer. The wiring possibly runs thru the same holes or close to the house wiring.
If it did not have the noise previously, then something has changed and light dimmers or flourescent lamps are highly suspect.
Kind of what I was thinking.
An alternative idea would be to check the capacitors. A lot of these units used a DC power supply that used one or more electrolytic caps to smooth the wave form.
In time, a decade or more, these electrolytics can dry up and stop functioning. Without their smoothing effect the bridge rectifier throws an unmodified square wave that produces a loud hum.
"An alternative idea would be to check the capacitors. A lot of these units used a DC power supply that used one or more electrolytic caps to smooth the wave form."
But that would affect it working in either direction.
I suspect a bad connection/broken wire.