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Retrofitting AM Contactor Cherry Switches..?

S

spinjector

Anyone ever do/see/hear of someone retrofitting the microswitches on their AM contactors with something else more durable? Such as a a beefier switch, or even solid state proximity sensors?

Even some kind of snap-in module with the same old Cherry switches would be better. Tiny little screws + big hands + small spaces + hard to access switch innards = pain in the butt. =-)
 
fm-engineer said:
Check with Kintronics. They have made some custom mods for me in the past.
Click to expand...

Ditto on Kintronic Labs.... good folks. You may also want to ask Kurt at Phasetek.
 
spinjector said:
Anyone ever do/see/hear of someone retrofitting the microswitches on their AM contactors with something else more durable? Such as a a beefier switch, or even solid state proximity sensors?

Even some kind of snap-in module with the same old Cherry switches would be better. Tiny little screws + big hands + small spaces + hard to access switch innards = pain in the butt. =-)
Click to expand...

KTL has a whole new line of linear actuator switches that are very smooth in operation and not as violent action as the solenoid operated versions. Attempting to substitute another type of Micro-switch or other hall-effect sensor might be exchanging problems for other issues. Both of these companies have these things down to a fine science and much better that the older versions. You might consider looking at how the actuator arm is engaging the micro-switches. It is entirely possible to have the actuator arm over engage the switch and that will make them fail prematurely. It literally beats them to death, I’ve see this a lot.

Working on those things in the middle of the night when it is 12 degrees can indeed help a sole develop quit a profanity vocabulary…
 
Hahaha. Yup. The problem is I'm one man with 12 towers x ~50 contactors x 4 = 200 switches. It seems like I'm changing one every month lately.
 
spinjector said:
Hahaha. Yup. The problem is I'm one man with 12 towers x ~50 contactors x 4 = 200 switches. It seems like I'm changing one every month lately.
Click to expand...
Oh my! I'll pray for you...
 
Wow...
Are you replacing the tally, the coil end of travel, or both? Are they failing mechanically? Or are the contacts burning or becoming corroded? That is too much current/voltage or not enough.

Think I've replace maybe half a dozen micrswitches in 30+ years and those were on those 60 amp jobs that look like a big version of a standard relay (not the rocker style). Those things would beat themselves and the micrswitches apart. Had 240 vac on the relays and tallys.

In ten years of maintaining a 6 tower with Harris rocker style relays and a four tower with Phasetek relays not one microswitch failure.
 
Boise, I think most of the contactors are the Kintronics 220v, 40 or 80 styles, the monster rocker ones... Actually that's the only kind I've worked directly with... They all have the little black & red Cherry switches about the size of a postage stamp... I've always eyeballed the Cherry switches with skepticism as to their durability, and considered them a weak point in the system... we used to have two engineeers, but the other was downsized, and he did a bunch last year, and I've done two so far this year...

I thought i'd ask because our 50kw has some switching problems, and i'm in the middle of fixing some things in the switching system... once i'm sure i've done all i can there, i'll have to start going through things in the doghouses, and it's either the switches, or something in one of those little Kintronics relay interface boards... and I figure if there's a "beefer-upper" kit, i'd use it if i found bad switches... the switcher had some bad diodes in it, and wouldn't do NDA1 mode, and last week Night mode died, but i managed to make it work... i'll see what happens after the diodes are replaced... there's eight of them and they're buried really deep in some spots, and it's hard working on it live... i have to go to Sh*t Shack and grab a bundle...

i can see where a previous engineer must have done this on the workbench some time in the past - there's a bag of diodes on the bench, and it's the same kind i'm replacing in the switcher... but he used 1N4001, which seems inadequate for the job, so I'm going to stop the goofing around and replace them all with something 10x the size like a 1N4007... they're only $0.25 each, and for the trouble they cause, it's not worth *not* replacing them since i have it all apart already anyways... all they're used for in the system is firing banks of cascading 24vdc K-style relay logic networks that in turn fire the contactors... my guess is either power surges, lightning, or relay reverse-whatchacallit when the coils disengage keep zapping the diodes...

and if that doesn't do it... off to the cherry switches... first in the phasor, then the doghouses...
 
The Kintronics have enough current through the contacts to self clean. Unlike a certain transmitter line that runs milliamps through the magnetic overload aux contacts. They build up resistance and fail and so does the transmitter.
 
Nope. They're FM's. Hit the plates on and it sits there, nothing. ??? Turns on the PA Overload light before it even tries to close the HV contactors. Have to burnish & treat the Aux contacts with Cramolin on the MAG coils couple times a year.

The talley contacts on phasors run enough current to make a bit of an arc & by design clean those contacts.
I have seen fireworks on AM contactors. ATU/tower was next to a powered tower and we were doing manual switching. Didn't throw it fast enough.
 
Nope...they are small relays with button contacts. Like boise says, the buttons get dirty and the transmitter gets stupid. You can stick a piece of paper thru the contacts and get them clean enough to work.

There's also a solenoid in the same general area of that transmitter that will cause impolite behavior if it isn't kept topped off with damping fluid.
 
I got off on two diff topics. Rocker switches: AM MAG Overloads: FM
What's in common are the tally contacts. AM Cherry switches have enuf "I" to clean them. FM MAG overloads don't since they're running only a few milliamps to the overly complex logic in those FM thingies.

Oh wait! If you look inside the MCI FM coax switches it is a rocker type switch! And I now remember having to relplace all 16 "Cherry" microswitches on 4 switches. A factory suggestion, but we still had to pay for the replacements.
 
Ah ok I always wondered what was inside those big metal FM switch buckets.

Hmm I just had an idea. For the rocker-style contactors that are vertically mounted, the Cherry switches could be replaced with mercury bulb switches like you'd find in an old residential thermostat. That would take care of all the oxidation & reliability problems. And if it got hit by lightning, it'd glow like a fluorescent light for a fraction of the second until the mercury vapor recondensed inside the bulb, and then go back to normal. :)
 
I don't believe I'd do that... the contactor will already be off the contact before the switch closes or opens. You want it to break or make befiore the roller moves in the fingers. One day someone will forget to kill the power before changing the switch, and the position safety is the last chance to keep from generating lightning.
 
So... After looking at (and swearing at) the blueprints for days, I finally did one long 14-hour marathon run to fix the switching system at my 50kw last night. I started at 10am and left at midnight. I did good, I think. The main problem was a bad solder joint on the "Kintronics Relay Interface PCB" on a contactor in one of the doghouses. Took me until about 9pm to narrow it down, then about 1/2 hour to fix it. Throughout the day I also found a mess of errors on the Kintronics RF system blueprints and switcher blueprints, and errors in the author-interpretation between the two. And errors in the construction of the switcher, and erroneous "repairs" by previous engineers - all most likely caused by the errors on the blueprints, which now have lots of corrections scribbled on them in pencil.

I honestly doubt the system has ever worked correctly since it was installed. To make it completely correct, I'll have to get a new front panel made with the contactor status lights in the proper locations. There's a status display board for the contactors, laid out in a row/column format, with lights for Day, Night, NDA1, etc. And because of the blueprint errors, the fabricator(s) drilled the holes for the lights in the wrong rows and used the wrong color lenses... LOL ;D
 
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