[Collins] 30S-1 Relay hang

[Dr. Gerald N. Johnson]

On Thu, 2010-02-18 at 21:01 +0000, Roy Reed wrote:
> 
> Subject: Re: [Collins] 30S-1 Relay hang   
> 
> Hi All,
>        Just want to say thanks to all who responded to my question re relay
> hang. I eventually got around to look at the problem yesterday. I applied an
> external 12v supply to the relays so I could safely observe both K101 and
> K205. It was K205 that was hanging. I had already swapped the coil supply
> leads around , did not make any difference but the coil has become
> magnetized. I have cured the problem by putting a piece of insulting tape
> between the coil and the clapper. I also gave the return spring a wee bit
> more tension. All is now working as it should.
>      Many thanks to all.
>                         73 Roy g3zig.
> 
> 
Now the problem could have been the spring had lost tension. Or the stop
has worn so the gap got smaller. The tape will cure that until it
smashes out of the way, then you will need a new layer of tape. A bit of
copper or aluminum foil might last longer.

It is practical to demagnetize that relay. You could try a loop of wire
replacing the tip of a Weller soldering gun. Loop the wire around the
extended tip of the core of the coil. Power the soldering gun through a
variable voltage transformer (a Variac) and after you hit the pole piece
with the full field, back off the voltage in a few seconds. That will
demagnetize the core. Else with the coil unhooked from any electrolytic
capacitors, apply AC probably about 20 volts to get the same AC current
as the normal DC current. Reduce that to zero in a few seconds, don't
turn the current off with either scheme when its near the full power or
you may magnetize the part worse.

The Weller soldering gun also works great with magnetized tools that you
don't want magnetized. Or if you turn the gun off with the tool in place
and full power you can magnetize the tool sometimes. Otherwise without
the variac for demagnetizing you just hold the gun power on and remove
the tool from the loop to demagnetize it.
-- 
73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association
All content copyright Dr. Gerald N. Johnson, electrical engineer