Contactors!

AM Radio discussion. Directional arrays are FUN!
sallen
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Contactors!

Post by sallen » Tue Sep 15, 2015 10:09 am

RF switching contactors are great when they work and switch fast, when they start to hang they become a real pain. I have two, maybe more Kintronics contactors that are hanging on pattern change. What do you do for regular maintenance for these contactors. Prayer beads, lubricate? Is there a way to guarantee the linkage works freely?

I also have a station using the MT 161-220-1 RF contactor. Any hints or tricks for them? Time to share your most cherished contactor memories! Maybe some advice or epiphany will hit me as I read the responses.

Thanks for sharing!

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Deep Thought
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Re: Contactors!

Post by Deep Thought » Tue Sep 15, 2015 11:17 am

In my experience, two things happen with the KTL contactors (short of a coil or microswitch failure): First the mechanical linkages get crap in them to the point where they start to bind up. If you can't flip the arm with your finger it's too stiff and a good cleaning and lubrication with something that manages to stay pliable at -20°F and doesn't attract moisture (i.e. not WD-40) is in order. While you're doing that, make sure the spring tension isn't set too tight. There are adjustments from the top and the bottom (between the solenoids) that are often overlooked. Second, the mechanical linkages wear and get too loose letting the solenoid shafts pop out of the coil too far, allowing them to get out of alignment. That is a real problem when they are mounted any other way but "up" and usually requires a complete disassembly to fix.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

grich
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Re: Contactors!

Post by grich » Tue Sep 15, 2015 3:12 pm

What Deep said applies to the Multronics contactors, too. Keep it clean and properly lubed. Check contact hardware to make sure nothing is shaking loose and that the contact finger cups are not missing any fingers.

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kkiddkkidd
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Re: Contactors!

Post by kkiddkkidd » Tue Sep 15, 2015 5:55 pm

I maintain a 4 tower DA2 with a Kintronics relay in each ATU and 3 or 4 in the phasor but in a the more temperate winters of southern TN. Almost 100% of the coil failures have been in the coldest weather that we typically experience. All the above applies... As well, If the RF contact surfaces are pitted but not completely missing fingers that is still a bad thing. Micro switch failures are a large factor in coil burnouts on this array.

A number of years ago, in a hypothermia induced semi-coma, I gave each contactor RF contact a healthy dab of Radio Shack Teflon gel lube. A few warm days later I wondered if the lube might be insulative. A few months later I wondered the same thing because I hadn't heard anything from the station owner thru several cold snaps. As it turns out, the Radio Shack Teflon gel was very friendly to the Kintronics contacts.

Upon later inspection, they (the contacts) were oddly colored (silver contact surface was greenish) but very slick and unpitted with no contact or coil failures. This array has always had numerous coil failures every winter.

Later,
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sallen
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Re: Contactors!

Post by sallen » Tue Sep 15, 2015 7:43 pm

Any tips on setting the tension springs? Is there some documentation? I may try a squirt of Tri-flow lubricant on the contactor on the bench that is slow in operation to see if that can clean and lubricate it. Tri-Flow makes several flavors has any one tried any of them on contactors? What lubricant have you used.

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Re: Contactors!

Post by ChuckG » Tue Sep 15, 2015 11:14 pm

Still have the late 50's EF Johnson contactors over here, same at every DA I've worked on. I don't use any lube on them, there aren't any parts that are machined that closely where friction is a real issue.
Oil does exactly the opposite of what I want.. it attracts dust, dirt, pollen, you name it and eventually cause the linkages to bind. I use automotive brake cleaner to clean the mechanical parts, then leave well enough alone. That stuff is flammable, so not while powered up.

I adjust the spring tension until the arms snap into place firmly when operated by hand, but not so tight the coils can't quickly reverse their position. Keep the contact fingers and shorting bars clean.

A problem I see quite a bit with "sluggish contactors" is a long run of control wire out to the doghouses causing a good sized voltage drop at the coils. If they are running on 110v the problem is twice as bad. I've had to ad a boost transformer at the phasor end to jack up the voltage on long runs.
Had a three-tower with #14 control wire - 1,300 feet of it...ended up sequencing the contactors through the microswitches so they operated one after another instead of simultaneously. There wasn't enough current available to operate all three at once unless the stars were correctly aligned.
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Deep Thought
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Re: Contactors!

Post by Deep Thought » Wed Sep 16, 2015 8:25 am

sallen wrote:Any tips on setting the tension springs? Is there some documentation? I may try a squirt of Tri-flow lubricant on the contactor on the bench that is slow in operation to see if that can clean and lubricate it. Tri-Flow makes several flavors has any one tried any of them on contactors? What lubricant have you used.
It is more important to keep everything clean. I've used a small shot of "Alumaslick" (intended for things like sliding door tracks, etc.) on the sliding surfaces in locations where corrosion is likely but other than that it's been a very light wipe of oil and not much else. The idea is to keep it all loose but not too lose, and avoid product that attracts dirt and moisture.

Chuck covered the spring settings. You want positive action, but not so stiff that it takes a prybar to get it to switch. You should be able to flip it with your fingers. And definitely check the voltage at the contactor during switching. They'll put up with about a 15% sag but that's about it, especially if wired for 120v.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

sallen
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Re: Contactors!

Post by sallen » Sat Sep 19, 2015 7:26 pm

I tried Tri-Flo on a contactor that was sluggish I had pulled out and was on the bench. I only sprayed the linkage and not the contactor contact or swing arms. It brought the contactor back to a quick position switch with no sluggish action. It did was out some grit or maybe dust that had settled into the linkage. I have used Tri-Flo on locks for a few years and it works great, leaves a clean lubricated surface and does not attract dust. Like WD-40 but no bad effects. So I then sprayed 5 contactors that were switching with sluggish action and all went to a nice fast switch. I do have to say that it is a lot easier cleaning and spraying out the linkage when the contactor is on the bench. The 5 contactors were sprayed in place trying to get the linkage and I was not able to wipe the linkage real well like the one on the Bench. I would gladly spray them once a year to keep the fast pattern change I have now. This is a 220volt system using #10 wire.

I called Kintronic and talked to Larry Arnold. He had not heard of Tri-Flo and was interested in how it rejuvenated the action of the contactors. I asked what kind of lubricant they used on the contactors and he said it was a Dow Corning product called 111 Valve Lubricant & Sealant. It's the stuff we use on "O" rings. It's silicon based with a wide temperature range. The one thing the Tri-Flo does the Dow Corning product does not do is the Flushing action of an arousal product. And easier application when a switch is buried in the back of a cabinet.
The company I contract with did spring for a new Kintronic contactor so I was able to observe a new contactor from the factory and see if there was any pre lubrication. I did find a thin coating of the Dow Corning compound on the linkage and actual contacts and swing bar "metal contact" bar. So to repeat the actual contacts had a thin coating of the Dow Corning Compound. I also had a contactor I was trying to improve sluggish action, I had already applied Tri-Flo to the lower linkage to flush and lubricate and wiped a thin coating of the Dow Corning product on the contacts. It now is switching like new as stated above.

When talking to Larry I mentioned the Break Cleaner and while it might be OK on the linkage he was worried that it might contaminate the fiber glass swing arms/arms. The original Johnson contactors have ceramic swing arms/arms so the break cleaner might be fine for them but use caution on Kintronic contactor fiberglass parts.

I also tried the Tri-Flo on the MT-161-220 and it helped. This contactor has a pivot point that uses a small amount of grease. Over time the grease dries and needs to be wiped out and replaced. Since I have three that were never installed but purchased 15 years ago they now needed the grease cleaned out and replaced with new grease to maintain quick action for future use or emergency replacement. I would also use the Dow Corning product on the MT-161 contacts. I have one more contactor to grease and may try the Dow Corning grease to see how well it works. I also use the Dow Corning grease for outdoor screw in lamps to help lubricate the socket and it makes removing the bulb in a couple of years easier, but with the LED ones I just put in who knows when I'll have to replace them. I'm glad Larry at Kintronic reminded me of the Dow Corning 111 Lubricant and it's many uses.

In 30 days I'll be checking the action on the 5 contactors sprayed with Tri-Flo and hopefully they will be fine.

sallen
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Re: Contactors!

Post by sallen » Sun Sep 27, 2015 10:56 am

Two weeks in and everything is still switching fast.

As it turns out I found another type of Dow Corning silicone based grease in a green tube. Dow Corning Compound 4. I think the main difference between the #111 compound and the #4 is that the #4 will set up where as the 111 stays more pliable. Is that right? Any one know the difference between the #111 and #4 Dow corning compounds?

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Re: Contactors!

Post by ChuckG » Mon Sep 28, 2015 6:57 pm

Thanks for passing along the info on the Dow Corning products!

Best I can tell, #4 is an electrical insulating compound that happens to have some lubricating properties, while #111 is a lubricant/sealant .
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Dale H. Cook
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Re: Contactors!

Post by Dale H. Cook » Tue Sep 29, 2015 7:43 am

Tri-Flo aerosol and Molykote 111 (the current designation for Dow-Corning 111) are both available in small quantities from Amazon. I have ordered both as I need to get cracking on winterizing ATUs.
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sallen
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Re: Contactors!

Post by sallen » Tue Sep 29, 2015 9:50 am

I'm curious, how low does your ATU temperature go? Do you do anything to try to keep it warm other than putting RF through the system. 200watt light bulb? Heater? What's affected most, Contactor action? parameter drift?

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Re: Contactors!

Post by ChuckG » Tue Sep 29, 2015 2:42 pm

sallen;

One site I worked at in Upper Michigan would hit -20 degrees or worse overnight some winters. That's where I got into the habit of not using any lubricant on the contactors, pretty much anything would get stiff. No lights, no heat in the ATU's.
The biggest problem was 1,700' of solid copper transmission line contracting in the extreme cold. If the center conductors didn't pull apart entirely (which they sometimes did) the parameters would noticeably drift.
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Dale H. Cook
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Re: Contactors!

Post by Dale H. Cook » Wed May 17, 2017 4:36 pm

ChuckG wrote:
Tue Sep 29, 2015 2:42 pm
One site I worked at in Upper Michigan would hit -20 degrees or worse overnight some winters. That's where I got into the habit of not using any lubricant on the contactors, pretty much anything would get stiff.
That is one reason why I use those specific lubricants. Dow Corning Molykote 111 (for the contacts) is rated for -40 to 392 degrees Fahrenheit (-40 to 200 degrees Celsius). Tri-Flow aerosol (for the linkages) is rated for -60 to 475 degrees Fahrenheit (-50 to 250 degrees Celsius).
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kkiddkkidd
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Re: Contactors!

Post by kkiddkkidd » Wed May 24, 2017 9:22 pm

Dale H. Cook wrote:
Wed May 17, 2017 4:36 pm
ChuckG wrote:
Tue Sep 29, 2015 2:42 pm
One site I worked at in Upper Michigan would hit -20 degrees or worse overnight some winters. That's where I got into the habit of not using any lubricant on the contactors, pretty much anything would get stiff.
That is one reason why I use those specific lubricants. Dow Corning Molykote 111 (for the contacts) is rated for -40 to 392 degrees Fahrenheit (-40 to 200 degrees Celsius). Tri-Flow aerosol (for the linkages) is rated for -60 to 475 degrees Fahrenheit (-50 to 250 degrees Celsius).
You lost me at the -40.
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