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Doorbell hum, but voltage reading okay?

I'm trying to fix a doorbell in a client's house. In one of four apartments a single chime unit in a bedroom hums after the bell's been rung a few times, so she (the tenant) can't sleep & must disconnect it. I tested voltage & it reads between 10-16 volts a/c, which my book says is what it should read. I'm not sure where the transformer is for this particular bell. There's three sets of 4-color wires running to one transformer mounted on main electric panel, but four doorbells, and I have yet to locate a second working transformer that might carry a fourth bell. What usually causes humming of a doorbell chime (when not being rung)? Could it be a loose connection in the outside ringer? How many bells can you run off one transformer?

Reply to
Peter Shepherd
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Replace doorbell with new unit. If not sure about the transformer, replace too.

Reply to
Brian

When not being rung, there should not be any voltage measured at the chime. Most doorbells are a simple series circuit consisting of switch button, power transformer, and chime. From your description, it sounds like the doorbell switch button is defective (intermittent - always on). I would suggest checking out the button and replacing it if necessary.

What else would would be causing the hum at the chime other then a voltage that shouldn't be there? Other possible causes could be an error in wiring or a short circuit.

Beachcomber

Reply to
Beachcomber

Some chimes have an extended operation sequence that uses a relay, or other device to extend the voltage present beyond the momentary period during the button press, and could be malfunctioning keeping voltage present at the chime.

As you advised checking the button would one of the first steps in troubleshooting.

With the information provided, I would discount the likelyhood of a short (unless it's in the conductors going to the push button). That leaves a defective button, or chime unit as the remaining candidates for the source of trouble. If the hum isn't coming directly from the chime unit (disconnect it to verify) it's possible that the laminations in the transformer (if it's close by) are separating, or even possible that the hum is originating from some other source.

More complete information regarding the layout, and components of the system could narrow the possibilities to consider.

Louis

Reply to
Louis Bybee

Are you sure the transformer isn't a part of the chime assembly? Perhaps its the transformer that is humming (ringing might shake a lamination loose occasionally).

If the transformer is mounted elsewhere, there should be no current running through the chime solenoid that could cause it to hum continuously, unless......

...the "outside ringer" (you mean the pushbutton?) might be getting stuck and causing a continuous current flow through the chime solenoid and a hum.

Many, because their duty cycle is very low.

Reply to
Paul Hovnanian P.E.

A stuck button.

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

"Peter Shepherd" wrote

Is the push an illuminated one? These usually have a bulb across the push contacts so it is constantly illuminated and a small current passes through the chime, not enough to ring it but possibly enough to cause a hum under some circumstances. Check voltage/current rating of bulb in push.

If doorbells, lots, because only one is usually rung at a time.

Owain

Reply to
Owain

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