[AMPS] Relays hanging up

Tom Rauch W8JI@contesting.com
Sat, 12 Aug 2000 09:28:52 -0400



> >> When we did that we could hear virtuallu hundreds
> >> of relays clickking off held by residual magnetism.

Well he "says" it was residual magnetism. I guess we have to 
believe somehow he knows that's what it was, and not weak 
springs or other mechanical problems.

> >Mechanical non-mercury wetted relays in a telephone switching 
> >system?
> >
> >What a system. No wonder the materials in the relay magnetic 
> >parts were poor!
> >
> €  ''poor''?  All relay armatures contain iron.  Hello.  If the spring
> isn't strong enough, it can hang up.  >........

That's right. With a weak enough spring, the relay won't have any 
return force.

But if the iron is soft it should also have no flux storage. If it does 
have flux storage, it would take a damn big hammer to 
"demagnetize" the metals in the relay.

I haven't seen ANY amplifier relays stick from "residual 
magnetism". I suspect the most common flaws...dirt or other 
contaminants....contact welding from hot switching...are written off 
to "sticking relays from residual magnetism".

I'm not saying it can't happen, just if the iron is too hard the relay is 
toast. It will immediately fail over and over again.

Magnetic flux isn't something that accumulates like pennies in a 
savings account.


73, Tom W8JI
w8ji@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com