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Dow key relay contacts.




 
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Author Topic: Dow key relay contacts.  (Read 4585 times)
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ka4koe
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« on: November 19, 2013, 09:24:43 AM »

My Dow Key started acting persnickety. When I would switch back to receive, the receive would be weak. I'd click the PTT again and it would clear up. I shot some Deoxit D5 in it and it seems to have cleared it up.

I assume this is normal since we're switching 150 watts of carrier; therefore, contact cleaning is a regular chore I would assume is required. Is this the best way to clean the contacts, eg. spray alone? I know better than to use a file since that will simply ruin the contacts.

tnx.

Philip
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WD8KDG
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« Reply #1 on: November 19, 2013, 11:38:35 AM »

Philip,

I wouldn't think the contacts on the receive side of the dow-key to be much of an issue. But with that said, both the receive thingy & the transmit thingy can be removed, cleaned, adjusted, etc. Please keep those files out in the garage Grin

So, if your dow-key relay is like mine, there is a little cover/peek hole on one end. Make sure the receive side is screwed in enough for good contact. Don't get carried away and not leave enough adjustment for that little arm to move from TX to RX.

Craig,
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KA0HCP
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« Reply #2 on: November 19, 2013, 01:04:05 PM »

Deoxit is a conductive spray.  The last thing one wants to do is slobber it around inside the contact area, since this could increase chances of arcing and carbon tracking.

I would clean with a plain, non-lubricated spray first.  Then if you want to use Deoxit, use a cotton swab and apply it carefully to just the contacts.
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KB2WIG
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« Reply #3 on: November 19, 2013, 03:21:50 PM »

I've used a trick from an old timer (w2wme) using a newish dollar bill. Gentely place it between the contacts, and draw it through.

Can't hurt to try.


klc
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KA2DZT
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« Reply #4 on: November 19, 2013, 03:34:41 PM »

I've used a trick from an old timer (w2wme) using a newish dollar bill. Gentely place it between the contacts, and draw it through.

Can't hurt to try.


klc

Question;  Will you get better results if one uses progressively larger bills i.e. 5s, 10s, 20s or even better, one of the new 100 dollar bills?

Fred
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« Reply #5 on: November 19, 2013, 03:49:02 PM »

One would think so, but not. The $100, Franklin, will not work, as it expects the electrons to be of a + charge. The $50, Grant, will grind the contact down, untill they give up. The $20,Jackson, will not always work if the equipment is a Apache, Mohawk, Chippewa, Seneca, Cheyenne or Comanche. It will only work to the west of the Mississippi River. The $10, Hamilton, faces the wrong way, and $5 Lincoln, didn't finish the last job (although it wasn't his fault). So you see, only the $1, Washington works. That's why our leaders want all of ours.


klc
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w4bfs
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« Reply #6 on: November 19, 2013, 05:59:31 PM »

One would think so, but not. The $100, Franklin, will not work, as it expects the electrons to be of a + charge. The $50, Grant, will grind the contact down, untill they give up. The $20, will not always work if the equipment is a Apache, Mohawk, Chippewa, Seneca, Cheyenne or Comanche. It will only work to the west of the Mississippi River. The $10, Hamilton, faces the wrong way, and $5 Lincoln, didn't finish the last job (although it wasn't his fault). So you see, only the $1, Washington works. That's why our leaders want all of ours.


klc

remarkable !
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W2PFY
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« Reply #7 on: November 20, 2013, 01:32:10 PM »

Quote
My Dow Key started acting persnickety.

The spray may do the job but if it comes back, I would suggest investing in burnishing tools.

When I used to repair electronic organs and piano keyboards, often times sprays would not do the job and I think while more dangerous than today's sprays, they were better at removing crud..............
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« Reply #8 on: November 20, 2013, 05:16:05 PM »

I used to use a 3/16" wide strip of crocus cloth, drawn through the closed contacts once on each side. But as fine as that stuff is, it may remove contact plating. Using rough paper is probably a better idea.
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Rob K2CU
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« Reply #9 on: November 22, 2013, 11:21:26 AM »

It is strange to have anything other than simple dry switching corrosion here. A strip of croakus cloth or even blue jeans (heavy cotton duck) should polish without stripping the silver plating. You may want to consider a T/R sequencer if you don't already have one. Essentially, you want to dry switch the relay, for transmit. It basically means, Switch antenna relay prior to keying transmitter, and unkey transmitter before releasing antenna relay. The usual setup has the transmitter relay power up the transmitter and also power the antenna relay. IN some rigs, the same relay does both with multiple contacts. usually, the antenna is switched over before the RF builds up, but is changed before the RF has decayed. So you end up hot switching the RF for going from Transmit to receive. Using two relays allows the sequencing to be set up with simple diodes, resistors, and capacitors in the relay coil circuits.
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The Slab Bacon
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« Reply #10 on: November 25, 2013, 11:51:45 PM »

I've used a trick from an old timer (w2wme) using a newish dollar bill. Gentely place it between the contacts, and draw it through.
Can't hurt to try.
klc

Kevin is on the right track here! The contacts on the receive side will tend to get some oxidation with age. the transmit side gets a "wipe" everytome it closes, not to mention that the power from the transmitter helps burn the oxidation off of them.

I usually take a dollar bill and dip it in a good contact cleaner or a 50/50 mix of mineral spirits and lacquer thinner and drag it between the NC (receive) contacts on mine. I usually find I have to do this every 5 years or so.

Frank
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« Reply #11 on: November 29, 2013, 07:41:09 PM »

Dollar bills are made with 100% cotton rag.  Good quality Bond paper is equivalent and won't have the grease and dirt from a hundred hands on it. Wink

p.s. BTW, I was taught to the dollar bill trick when I was operating TTY and crypto gear in the Navy.
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KA2PTE
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« Reply #12 on: March 26, 2021, 03:59:57 PM »

I have one that is 120V operated, and wanna clean the coax contacts. How do you access them?



* dow-key.jpg (706.57 KB, 1392x1104 - viewed 66 times.)
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KB2WIG
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« Reply #13 on: March 26, 2021, 04:49:46 PM »



Use your thumb nail and lift the silver cover on the end. Inside are the coax contacts. Good luck getting anything in there. In the past, I've used a piece of a $bill to clean contacts; grab  some tweeezers/hemostat/allie gator clip and have at it.  good luck cleaning the contacts.

klc
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MikeKE0ZUinkcmo
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« Reply #14 on: March 27, 2021, 05:01:35 PM »

I used a Dowkey relay long long ago, and had similar problems, then I bought a Johnson T/R switch.   Sold the relay, kept the switch.   Haven't ever needed to clean the contacts either. Grin
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« Reply #15 on: March 28, 2021, 05:06:12 PM »

I had a dow-key relay problem a while back in which the center pin of the receive side SO-239 socket did not make good/tight electrical contact with the center pin of a standard PL-259 plug.

I fixed the problem by using a 0.5 inch wide piece of aluminum foil... rolled up into a cylinder that was just wide enough to insert into the SO-239 socketís center pin.

Then I pushed the PL-259 plug into the socket... crushing the aluminum foil insert.

Stu
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« Reply #16 on: March 29, 2021, 01:26:20 PM »

I might have taken a dental probe (thin point) or a tiny jeweler's screwdriver and gently
urged the springy fingers of the socket toward the center...

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WA1QHQ
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« Reply #17 on: March 29, 2021, 03:00:04 PM »

I was restoring a Collins autotune mechanism and the relay contacts were fairly corroded, that is open circuit corroded. I tried every trick there was short of filing/wire brushing the contacts which would be bad news. i finally arrived at a decent solution, 1500 grit wet dry sand paper soaked in DeOxit. Tear the sand paper into long thin strips and fold it over on itself so that you have double sided sand paper strips, soak in DeOxit. Now gently draw the sandpaper between the contacts and watch the contact resistance go back to where it was when new.
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« Reply #18 on: April 01, 2021, 05:32:15 PM »

I like to use a strip of stiff paper cut to fit between the contacts.  I soak the paper in a bit of alcohol, put the paper strip between the contacts and push the contacts closed while pulling the paper out.  Doing this a few times will usually do the trick.
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