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Author Topic: Dow-Key antenna switch  (Read 1898 times)
W9BVG
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Posts: 10




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« on: November 06, 2017, 03:36:41 PM »

Anybody know how to stop the switch from chattering (repeating, rapid make/break action because solenoid doesn't stay in position when activated)? My switch is circa 1959 manufacture date. I'm just starting to use the switch again after having been off the air for years. 
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N4UE
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Posts: 709




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« Reply #1 on: November 06, 2017, 04:02:50 PM »

What model/voltage? I have several dozen Dow-Keys, from 12 to 220 volts. None chatter.
They made a LOT of different relays. Perhaps, you are trying to power a 12 VDC unit with less than the required voltage.

ron
N4UE
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W9BVG
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« Reply #2 on: November 06, 2017, 04:20:48 PM »

Hello Ron,

Mine is a 115 VAC model and I'm powering it with that voltage. Maybe I'll try opening it up and see if I can reduce the spring tension on the contact arm.

      -Chuck/W9BVG
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K8AXW
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« Reply #3 on: November 06, 2017, 10:22:48 PM »

Chuck, before I'd do ANY adjusting I'd do a little cleaning and lubrication first.  I've never had a DowKey relay chatter.

Whenever dealing with something that old, usually most problems with them centers around cleanliness (which includes a layer of rust on the armature) , lubrication and cold solder joints.

Of course contact corrosion is almost always present but that doesn't cause "chattering."
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W1VT
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Posts: 2529




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« Reply #4 on: November 07, 2017, 06:58:18 AM »

Two reports of exactly this problem.

http://puck.nether.net/pipermail/boatanchors/2006-October/016334.html
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

After 50 years the permanent magnets used in these relays may have deteriorated.
« Last Edit: November 07, 2017, 07:08:04 AM by W1VT » Logged
W9BVG
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Posts: 10




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« Reply #5 on: November 07, 2017, 10:58:29 AM »

K8AXW,

Thanks for reply....Before making any adjustments I did apply some powdered graphite to the part of the armature I could see (without opening the solenoid and removing it). I didn't see any rust. That didn't stop the chatter, so I next tried changing the tension of the antenna contact arm by moving the "receive" SO239 jack in and out...again, no go. Then I tried narrowing the gap between the "transmit" SO239 jack contact and the antenna arm by moving the jack inward. That seems, so far, to have stopped the chatter; on a few activations of the solenoid there's a little vibration left, but, according to a continuity check with the DMM on the tone position there's no interruption of the antenna arm/transmit circuit. Maybe I'll pull the lid off the solenoid and pull the armature to see if there's any rust on the part I couldn't see before.

W1VT,

Thanks for reply....Guess I COULD have a weak coil....wonder how K5IZ determined his was weak (short of comparing pressure of armature "push" with a new solenoid). Noticed you referred to a permanent magnet in the solenoid. Don't they only use an electro-magnet?
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W1VT
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« Reply #6 on: November 07, 2017, 12:57:09 PM »

If only electromagnets were used, what would cause them to deteriorate with age?
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W9BVG
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« Reply #7 on: November 07, 2017, 01:46:04 PM »

If the insulating enamel coating on the copper wire winding can deteriorate (?) would that cause a progressive shorting process? If so, suppose the magnetic force would decrease.
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W1VT
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« Reply #8 on: November 07, 2017, 02:36:49 PM »

You should be able to measure a short as a decrease in resistance and increase in current drawn.
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N3QE
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« Reply #9 on: November 07, 2017, 03:58:28 PM »

Is the shader ring in place on top of the coil? It is a copper ring that goes over part of the pole piece and I think it was originally held on either with a friction fit or maybe some enamel.

If it has gotten knocked off over the years then the relay will indeed buzz horribly on AC. You might be able to succesfully operate it on, for example, 24VDC or 48VDC if the shader ring is gone (use the lowest DC voltage that will work).
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KL7CW
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Posts: 264




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« Reply #10 on: November 07, 2017, 05:36:18 PM »

I have also operated AC relays with DC voltages.  See how much DC you need to pull in the relay, then increase it by perhaps 25 % or something for reliable operation.  I do not remember exactly how much DC I needed to use for reliable operation of a 120 v AC relay, but it might have been something like 24 or perhaps 36 volts DC Huh? this was many years ago.  Even if you can get rid of the chatter with AC, some relays/solenoids still tend to have some hum with AC, so going to DC may actually be an advantage.  I believe some AC hum was common on Dow Key relays...no problem with commercial applications, but kind of distracting in a quiet ham shack.
           Rick  KL7CW
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W1VT
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« Reply #11 on: November 07, 2017, 05:45:09 PM »

In 1959 it was quite a bit harder to run a relay off DC than AC.  Cheap and easy silicon rectifiers weren't available yet.
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K5LXP
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WWW

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« Reply #12 on: November 07, 2017, 06:13:16 PM »

In 1959 it was quite a bit harder to run a relay off DC than AC.  Cheap and easy silicon rectifiers weren't available yet.

But 'B' batteries were.

 Wink

Mark K5LXP
Albuquerque, NM
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W1VT
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Posts: 2529




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« Reply #13 on: November 07, 2017, 06:22:51 PM »

A QRPer's challenge--working WAS or DXCC on a single set of batteries!
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K1DA
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Posts: 724




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« Reply #14 on: November 20, 2017, 07:38:46 AM »

I found using Dow Keys as antenna relays  for high power  antenna switching (before I switched to vacuum) that a DC power supply that supplied a high pull in pulse but dropped to a lower steady state voltage for hold in provided good switching time without burning up the coil. 
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