Gates 5. Again.

AM Radio discussion. Directional arrays are FUN!
Post Reply
ChuckG
Posts: 874
Joined: Tue Mar 11, 2008 11:12 pm
Location: Moo
Contact:

Gates 5. Again.

Post by ChuckG » Thu Jul 28, 2016 11:35 pm

Granted it's been a stormy summer with lots of lighting, but here we go again. Gates 5 output network damaged for a second time within months, this time while operating in DA mode at 500W.
Electrical storm had passed through a few hours earlier, but it was relatively mild.

PA Tuning control arced at the variable tap and to the front panel, destroying the variable tap finger and part of the coil winding itself. VSWR Shutdown, thankfully saved the PA boards.
20160728_163234.jpg

Front panel with the Tuning inductor removed showing one of the scorch marks. I have no idea why the pic is sideways.
20160728_163330.jpg

Here's the remnants of the damage from last time when it blew the output network caps. Pic shows the replacement caps and cleaned-up tubing & insulators. That black crap just doesn't want to come off of the aluminum, even after an alcohol scrub.
20160728_163453.jpg


There's something going on here but I don't know what. I'm not having this problem on any other Gates-series AM I maintain.
Tower arc gaps are in good shape and adjusted to just beyond the point where they arc on modulation.
Two turn loop in the RF Feeders.
Ground straps are solid, screen and radials are good, at least where I can access them.
4" strap from transmitter to tower ground rings, appears solid where I can see it.
Lea Dynatech AC line suppressor at the breaker box.
Pa volt/amp ratio matches the checkout sheet, VSWR is zero, bridge shows the load @ the transmitter output is correct.

What am I missing?
<><><><><><><><><>
Chuck Gennaro
Central Wisconsin

User avatar
Deep Thought
Posts: 3124
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: Gates 5. Again.

Post by Deep Thought » Fri Jul 29, 2016 7:49 am

Was that coil replaced in the previous incident? If not it may have been weakened then and finally just let go. Had a similar coil of similar vintage decide to end it all in a phasor awhile back...the normal 8 amps of RF current in a 20 amp coil did this:
DSC01432.JPG
Failure point was the finger "tips".
DSC01443.JPG
Transmitter driving the phasor (an SX-5) is not even capable of feeding enough current to the common point network (this was the common point input coil) to cause an over-current situation. It took 30 years, but it happened. No lightning, no system disturbances, just a normal day. * poof *.

Not much help here but another data point.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

Kelly
Posts: 474
Joined: Thu Aug 21, 2008 5:32 pm
Location: Washington D.C. Area

Re: Gates 5. Again.

Post by Kelly » Fri Jul 29, 2016 10:41 am

MMmmm, Krispy Koil!
Skype:kellyalford Twitter: @KellyAlford

User avatar
Shane
Posts: 705
Joined: Fri Feb 01, 2008 12:08 am
Location: Omaha
Contact:

Re: Gates 5. Again.

Post by Shane » Fri Jul 29, 2016 10:56 pm

Kerosene will get the black goop from the blown micas cleaned up. I had the privilege of doing such a cleanup on an RCA BTA50H1(or 2).

Funny part of the story was we couldn't find a kerosene can at a local store so we got a gasoline can and showed up at the kerosene retailer who, rightly, refused to put kerosene in a red can.

Armed now with the information as to what color it needed to be, we went back and bought a can of blue spray paint and Voila! We got our kerosene and a few good laughs about it.

Fast forward 20 years and my stepdaughter ran out of gas for the lawn mower so she grabbed the blue can and put that in it. No laughs.
Mike Shane, CBRE
---Omaha---

User avatar
NECRAT
Site Admin
Posts: 2900
Joined: Sat Nov 17, 2007 9:13 pm
Location: Taunton, MA
Contact:

Re: Gates 5. Again.

Post by NECRAT » Sat Jul 30, 2016 4:47 pm

Shane wrote: Fast forward 20 years and my stepdaughter ran out of gas for the lawn mower so she grabbed the blue can and put that in it. No laughs.
Did you at least get a video of the fire?
http://www.necrat.us

"Arguing with an engineer is like mud wrestling with a pig. After a couple of hours, you realize the pig likes it"

ChuckG
Posts: 874
Joined: Tue Mar 11, 2008 11:12 pm
Location: Moo
Contact:

Re: Gates 5. Again.

Post by ChuckG » Sat Jul 30, 2016 9:48 pm

Shane wrote: Fast forward 20 years and
You managed to keep a gas can for 20 Years? I don't know whether to laugh, or bow.

I think the staff would call the cops if they saw me heading towards the transmitter with a gas can at this point. " Oh yeah, that tar's gonna come right off, you bet it is". :lol: :evil:
Ironically the matching Gates 5 I'm using as a standby did survive a transmitter building fire.
<><><><><><><><><>
Chuck Gennaro
Central Wisconsin

User avatar
Shane
Posts: 705
Joined: Fri Feb 01, 2008 12:08 am
Location: Omaha
Contact:

Re: Gates 5. Again.

Post by Shane » Sun Jul 31, 2016 11:42 pm

Did you at least get a video of the fire?
Heh. Had there been a fire. All I got was a mucked up engine that should be salvageable but I wasn't successful on the first two attempts. I am told Kerosene has an octane rating of about 25 so you can see why it wouldn't burn in an engine that was expecting to be able to breathe.
You managed to keep a gas can for 20 Years?
No, but I am always mystified by the fact that everybody else has to use Stabil in the gas they hold over from the previous mowing season and drain the tank and carburetor bowl on the machines they will put this gas into. I have never had that problem. I almost never use Stabil nor drain the gas from my mowers and snow blower but they always start right up the next season.

Except the one that had the kerosene put in it.

I had a friend give me a 5 gallon metal can of kerosene that had been sitting around for he-didn't-know-how-long and I kept it hanging around for about another couple of years. Then I put some in the kerosene heater as a test; no ill effects. Ended up burning all of it.

(The thing I like about a kerosene heater is that you've already paid the bill for the heat!)

Now about taking gasoline to the transmitter.... Gasoline is good for cleaning stuff but I wouldn't (although I can think of a few ATU houses that would have been improved by setting then on fire). I can't remember who suggested we use kerosene to clean the mica cap gunk out of the transmitter but it sure did work.

We never did get that transmitter back up to full power again, though a 25kw backup transmitter ain't bad. Sometime after I left the station, they dismantled the old girl and put in a DX-50 relegating the Continental 317-C3 to backup duty. Just going by how many of the 50kw stations of the 70's and 80's had some form of 317 is a testament to those rigs. They may have been the best 50kw transmitter ever made that still used some tubes. IMHO, of course, and in my limited experience with those kinds of rigs.
Mike Shane, CBRE
---Omaha---

awsherrill
Posts: 234
Joined: Fri Nov 16, 2007 10:30 pm
Location: Raleigh NC

Re: Gates 5. Again.

Post by awsherrill » Mon Aug 01, 2016 10:15 am

Mike, your story reminds me of something my daughter did a couple of years ago. She took our old Honda Accord to a gas station, and somehow managed to put a full tank of diesel in it. I'm wondering how she got the nozzle to fit in the Honda's filler tube without spraying diesel everywhere.

Then she drove about ten or twelve miles, almost made it to her boyfriend's house before it died. Got it towed back home, and in the meantime we did the twenty questions with her, and figured out what happened. Long story short, I managed to suck all the diesel out of the tank and put some fresh gas in. Got it running and it's been fine ever since.

We still call it the "diesel Honda" :lol: I guess it would take more than that to kill that car.

Back on topic, I've never seen coil damage in a phasor like that shown in Deep's pictures. Wow. I did have to replace sliding contacts in a couple of coils in one of our phasors a few years ago. The contacts had welded to the center shaft and you couldn't adjust the coil anymore. Working on a similar situation in a phasor at another station currently, not quite to the same extent of damage yet. We will be cleaning them up and applying silver conductive grease to the moving contacts.

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests