Dow Key relay chatter problems

[Mike Langner]

Hello George and Rick -- and the list !

Don't throw away those relays !  You probably don't need to rewind that coil
(unless it has shorted windings) !!


Here's a trick from aretired old broadcast engineer as well as from a 50
year amateur op --

Put a diode in series with it -- and it'll probably shut up.  If it still
chatters, try just a few microfarads of capacity -- you don't want too much
capacity or you'll create a time-delay circuit.  The coil will act as a
choke to the pulsating DC -- a little capacity, if needed, will damp out the
remaining chatter.

If you can't get the chatter to quit without so much capacity that you get
an unwanted time-delay circuit, use 4 diodes in a bridge -- then you'll have
120 Hz pulsating DC instead of 60 Hz pulsating DC. The 120 Hz will be less
likely to chatter and if any capacitance is required, it'll take less of it.

Do check coil temperature after it's been on for a while to make sure you're
not over-dissipating the coil -- most AC relays work well on significantly
less DC, and when operated on pulsating DC, the voltage to use tends to be
typically 79 to 80% of the AC RMS voltage -- your mileage may vary.

We used to use this trick with "chattering contactors" in broadcast
transmitters as well as when we had to run AC relays on DC.

It always worked like a charm !

Mike/
K5MGR
_____

-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTSERV.TEMPE.GOV]On Behalf Of Rick Brashear
Sent: Sunday, October 01, 2006 3:09 PM
To: BOATANCHORS at LISTSERV.TEMPE.GOV
Subject: Re: Dow Key relay chatter problems


Hi George,
I finally discovered the problem with my "chattering" relay was a weak
coil winding.  It too was 115 vac relay.  I guess time took its toll.  I
laid it aside telling myself I'll rewind it one day. ...we'll see.
73,
Rick/K5IZ


George Maier wrote:

>I have three Dow-Key 110VAC coaxial relays. Two are the older black body
DKC
>type and one is a newer silver body DK60 type.  When actuated, the two
black
>body relays seem to hum and chatter regardless of how the tension is
>adjusted between the internal contact and the transmit connector.  The
newer
>relay works flawlessly, as do all the two 110VAC Advance relays that I
have.
>Short of pitching the Dow-Keys in the dumpster, does anyone know of cure
for
>this behavior?
>
>Thanks & 73,
>George - W1LSB
>
>
>
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