Technical Advice - Door
I think the
attraction for me about door chimes is that they are perhaps the
first piece of electro-mechanical automation that was available
to average people for their homes. Just the idea of pushing a button
and having some solenoids do a little job for you is entertaining.
In simpler one
or two tone chimes, the instant the door bell button is pushed,
the solenoid is activated via a direct path circuit and the bell
sounds right away. The electrical path is a bit more complex in
a 4-tone chime. As described above, the power needs to be sequenced
through the distributor. When the door bell button is pushed, that
turns on power to the motor that drives the distributor, the commutator
starts moving, and only once the commutator touches the first contact
does the chime sequence start. In models with a rotary distributor,
the door bell button has to be pressed and held momentarily in order
for the commutator to overcome the start resistance in the distributor
assembly. All of this is entirely normal, but might seem odd to
those familiar with the immediate action of simpler chimes. The
start resistance in the distributor can cause a problem though.
In some models the start resistance can be adjusted. Too much resistance
and the distributor will not start. Too little resistance and the
distributor will not stop and the chime sequence will replay indefinitely.
Some older mechanisms
have a number of natural rubber parts in the unit assembly. Each
subassembly is attached with rubber grommets, presumably to deaden
any vibration or mechanical noise that could detract from tone quality.
In addition, the caps that retain the plungers and springs inside
the solenoid cylinders are often made of the same natural rubber
material. Natural rubber has the nasty habit of drying out and turning
brittle or crumbly as it ages—and forty or fifty years is
beyond its life expectancy. As a result, these older mechanisms
are in need of refreshed rubber. Rubber grommets and neoprene washers
are readily available at any well stocked hardware store, so getting
replacements for these parts is no problem. Doing the R&R on
the grommets is time consuming but not especially difficult.
caps however represent a different sort of problem. I recently found
one vintage mechanism that was missing the plungers and springs.
At first I thought the unit had been scavenged for parts, but after
more thought, arrived at the theory that once the caps had become
adequately decrepit, the plungers broke the caps away on the rebound
stroke and were lost forever. Whether or not it happened that way,
the problem remains certain that the ancient rubber caps fail. This
really complicates the solenoid cleaning process described above
—if removed, the caps will crumble and need to be replaced.
Oh yeah--- and if the rubber washers and caps parts have decayed,
there is a really good chance that the insulation on the wiring
has also gone the same route.
a quick survey of some of the common mechanisms and generally how