[Boatanchors] Relay Repair - Demagnetization Question

[mac]

Mark,

You essentially introduced an "air gap" between the coil core and the  
relay armature.  The residual magnetism wasn't strong enough to hold  
the armature closed across the gap.  Definitely a solution.......

Dennis D. W7QHO
Glendale, CA



On Feb 2, 2010, at 9:00 AM, Mark Foltarz wrote:

> I experienced the phenomenon with a Scott 800 radio.  The mute relay  
> kept sticking and by all appearances it was the coil and core
> staying magnetized. Indeed the relay uses DC.
>
> After a lot of head scratching I placed a piece of scotch tape  
> across the coil assembly to prevent it from making contact with the  
> contactor arm (terminology ? )
>
> Has not stuck since.
>
> de KA4JVY
>
> Mark
>
>
>
> ----- Original Message ----
>> From: Glen Zook <gzook at yahoo.com>
>> To: boatanchors at mailman.qth.net; Ron <ronami at yahoo.com>
>> Sent: Tue, February 2, 2010 11:31:22 AM
>> Subject: Re: [Boatanchors] Relay Repair - Demagnetization Question
>>
>> In theory, yes.  But, unfortunately, in reality, no!  There are all  
>> sorts of
>> relays "out there" that, when run from DC, definitely get  
>> magnetized.  The "fix"
>> is to reverse the connections periodically.  Now when run from AC  
>> the problem
>> doesn't exist.
>>
>> Glen, K9STH
>>
>> Website:  http://k9sth.com
>>
>>
>> --- On Tue, 2/2/10, Ron wrote:
>>
>> Relays are designed with very low coercivity (or remnance) cores.  
>> There is no
>> need to ever demagnetize a relay.
>>
>>
>>
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>
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