My multi-pin connector threw up in the transmitter room

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NECRAT
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My multi-pin connector threw up in the transmitter room

Post by NECRAT » Wed Apr 18, 2012 1:40 am

So one of our ENG receive sites has been having an ongoing issue of "chewing" through PTI boards on their Troll System slaves.
Well it got to the point where the Troll Slave was blowing fuses almost instantly. After a bunch of troubleshooting, I noticed something odd on the connector

Image
While it's hard to see here, but there is oxidation on the multi-pin connector. This connector is on the end of a cable that starts here and goes up 800 feet up the tower, and is not enclosed in a conduit. This connector, however, sits on a surge suppressor, indoors. The cable, goes into a cable tray from the tower bridge, down a rack, around a 180° bend, and into the surge unit. So why is there oxidation? There are no signs of water damage above the rack or on any of the shut off analog gear in the rack. On a suggestion from an engineer at MRC, I decided to open up the connector... and upon doing so... you can see, it vomited all over the floor

Image
Image
Needless to say, now I have a much bigger problem, need to figure out how water is getting inside the cable (I am guessing the jacket has a breach somewhere, and it is travelling inside the jacket) and also need to come up with a way to "drain" the cable to prevent future problems. (And I can tell that I need to replace the 28 pin connector too...)

Ah the life of an engineer...
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Re: My multi-pin connector threw up in the transmitter room

Post by w9wi » Wed Apr 18, 2012 6:06 am

This happened to us.

I wasn't involved in the repair so I don't remember what we did, but I'll see if I can find out.

One thing we did do was to reroute the cable so it approaches the equipment from below.

(we had that option, because the equipment is on the second floor of the transmitter building)
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Re: My multi-pin connector threw up in the transmitter room

Post by PID_Stop » Wed Apr 18, 2012 6:49 am

Had a similar problem here many years ago, and ultimately wound up cutting the cable and fanning the wires to the bottom of a barrier strip on the wall near where the cable entered the building. The incoming cable came down from above and the outer jacket was stripped just to the left of the strip; the wires formed a "U" to come up to the terminal screws. Essentially, it formed a drip loop. Then the cable continued from the top of the strip to the mil spec connector. Not only did this stop the water accumulation, it gave us an opportunity to put transient suppression on the lines -- which solved a few other problems.

Ironically, there has been no sign of water getting into the cable since then, making me wonder if there was moisture inside the line when it was manufactured, and it just migrated down over time. (Never seen this before and it seems rather unlikely, but I can't come up with a better theory.)

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Re: My multi-pin connector threw up in the transmitter room

Post by grich » Wed Apr 18, 2012 10:20 am

We did a similar thing to a two-conductor cable that goes up to a preamp (We have two preamps...the top preamp at 1800 feet is coax-powered, and having the top and mid-level (900 feet) preamps powered thru separate paths helps a lot in troubleshooting). The cable loops to the floor, comes back up a foot, then is fanned out to connect to the power supply. Water oozes out of the jacket on occasion and just drips to the floor. In your case perhaps a loop to the floor, and a carefully-placed slit through the outer jacket at the low point would allow seepage to drip out into a bucket or tray.

Glad we don't have that much Troll cable to worry about...the above installation only has two wide horns combined together. Our second site has a 4-sector antenna but the multi-conductor Troll cable is only about 80 feet long on top of a building.

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Re: My multi-pin connector threw up in the transmitter room

Post by NECRAT » Wed Apr 18, 2012 12:49 pm

PID_Stop wrote:Had a similar problem here many years ago, and ultimately wound up cutting the cable and fanning the wires to the bottom of a barrier strip on the wall near where the cable entered the building. The incoming cable came down from above and the outer jacket was stripped just to the left of the strip; the wires formed a "U" to come up to the terminal screws. Essentially, it formed a drip loop. Then the cable continued from the top of the strip to the mil spec connector. Not only did this stop the water accumulation, it gave us an opportunity to put transient suppression on the lines -- which solved a few other problems.
That is quite funny you mention the Barrier Strip. That is my plan as well, I am going to break out to a Barrier Strip prior to the Surge box, with a "drip loop" configuration.
I am also going to make sure the Barrer Strip is in "Alphabetical order" in accordance with the pins, as it will provide an excellent test point. My only fear is that the moisture is from a deeper breach than the jacket, and we may be having a bigger failure. And go figure, it's the longest run of cable (1000') of all my sites.

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Re: My multi-pin connector threw up in the transmitter room

Post by PID_Stop » Thu Apr 19, 2012 10:38 am

NECRAT wrote:I am also going to make sure the Barrer Strip is in "Alphabetical order" in accordance with the pins...

-- Mike
Hmmmm. I can see it now:
  • • Eight
    • Eleven
    • Five
    • Four
    • Nine
    • One
    • Seven
    • Six
    • Ten
    • Three
    • Twelve
    • Two
:P

-- Jeff

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Re: My multi-pin connector threw up in the transmitter room

Post by NECRAT » Fri Apr 20, 2012 10:57 pm

Oh no no, it's the true RadioWaves way. (Actually this is the standard for this connector.)

ABCDEFGHJKLMNPRSTUVWXYZabd

And the "jumper" diagram has Z connected, where the tower connection shows R connected.

FYI, if you're ever looking for the connector Mouser Has them for $45.54/ea.

I have a bunch of Troll, Interconnect and other documents, in case anybody ever wants them... PM me with an email.
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Re: My multi-pin connector threw up in the transmitter room

Post by NECRAT » Thu May 03, 2012 8:15 pm

I am happy to say, that this site is back in service again, after today's visit from the tower crews to seal up the connector on the antenna, who's weather sealant dried up.

And because everyone loves tower p0rn, here is a photograph from under the antenna looking down, taken today. 800' up.

Image
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Re: My multi-pin connector threw up in the transmitter room

Post by Baylink » Tue May 15, 2012 10:07 pm

Proof that I am not a tower guy: just looking at that *picture* scares the everlovin' crap outta me.

But I gotta ask: what was that cable driving? That many pins?

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