Brian Lawson wrote:
On Tue, 24 Jun 2008 15:38:56 -0500, Ignoramus19021
wrote:

SNIP

It is BUUUZZZZZZZZZZ

Like a cheap 60 Hz alarm.


The first, which it sounds/reads like to me you have, can be just some
accrued dust or similar in between the armature pieces, possible even
a low voltage condition.

But the louder and sometimes scary sound can be due to a loose or
broken lead or cracked StaKon terminal (common on AB stuff) or a bad
self-holding contact.

I will look again, try to blow out the crud with compressed air, I
suspect insects at this point as Pete C said.



Hey again Iggy,

The AB stuff is pretty easy and straightforward to take apart for
inspection and cleaning. I doubt that blowing air will do much, but
hey!!

The "60 cycle buzz/hummmm" is caused by the armature pieces not
getting to a full flat contact, or possibly by a (very rare) cracked
shading-coil. The shading-coil is the copper flat buss in the form of
a figure-8 on the fixed armature part.

A few years ago while visiting a friend in Florida I was asked bt him to
investigate a buzzing noise from an irrigation pump motor control relay
mounted in a not very well sealed outdoor housing.

The problem was similar to what you suggest, but instead of being
cracked, the shading coil had corroded away, leaving not much more than
a blueish green trace of its former self.

Must have been a lot of humidity inside the housing leading to galvanic
corrosion of the shading coil.

We went to a supply house, bought a new relay, and installed it.

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*1014 fathoms per fortnight.


Other than the noise annoyance of the buzz, it's not really a problem.

Take care.

Brian Lawson.