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Rebuilding a Lighting Choke

Posted: Wed Sep 14, 2016 1:50 pm
by Jim Sofonia
My previous assistant is faced with a shorted AC lighting choke. The last time we replaced one of these it was very expensive ($3500) and took like two months to get it. So he is considering rebuilding it, but not shure what to use for the insulation between the windings. I thought maybe that orange stuff krypton tape or film. Has anyone here ever rebuilt one of these. The equipment is a Harris atu running at 580 khz, so longer than most other TLC's. It has three windings, beacon, side lights, and neutral.

Re: Rebuilding a Lighting Choke

Posted: Wed Sep 14, 2016 3:35 pm
by ChuckG
I've rebuilt three of those, but they were the old Andrew chokes with flat wire. I used insulating varnish on the windings
as needed and a sheet of insulating paper I got from a local motor rewinder between layers.

Re: Rebuilding a Lighting Choke

Posted: Thu Sep 15, 2016 8:53 am
by rich wood
Chuck,
Give Greg Albert at WJJQ in Tomahawk a call, I believe he still has a single circuit 110 v lighting choke on hand. It was used in his 1 kW ATU and worked when I pulled it out of service.

Re: Rebuilding a Lighting Choke

Posted: Thu Sep 15, 2016 9:07 pm
by ChuckG
Hi Rich;

Thanks for the tip. Perhaps they have what Jim needs.
The three I rebuilt were up at WJMS, about 20 years ago. I planned on replacing them with new Kintronics chokes, but found the new chokes, at least at 590Khz, threw the DA so far out of whack I didn't have enough ATU coil to bring it back. Thus the old ones got re-wound. They probably have the new ones still sitting on the shelf up there.

Re: Rebuilding a Lighting Choke

Posted: Sat Sep 17, 2016 1:46 pm
by BigRed
Have you tried:

Phasetek in Doylestown, PA? They build phasing and tuning equipment for AM stations.

Commercial Radio? They may have what you need too. http://www.commercialradiocompany.com/

And, sadly, the used market? A number of AM stations have gone "dark" (silent) recently. Just saw that a station outside of Chicago has their 15-year-old Pi Rod towers up for sale. $1 takes them all (the caveat is that you have to dismantle and remove them from the site, before the end of this month. Be sure you have at leas $2-million in liability insurance before inquiring). It's possible that someone like that might have an entire LTU available for cheap.

Re: Rebuilding a Lighting Choke

Posted: Sat Sep 17, 2016 3:16 pm
by Deep Thought
Unfortunately, as noted above you can't use just any lighting choke on the bottom of the band so the used market is going to be kinda hit or miss.

The one outside Chicago had unlit towers and had been a loser for decades. Newsweb did a nice job rebuilding it to give the place one last chance but the daytime mostly covered Gary, Indiana and the nighttime didn't cover much of anything due to the high night limit.

Re: Rebuilding a Lighting Choke

Posted: Sun Sep 18, 2016 11:23 pm
by BigRed
Deep Thought wrote:Unfortunately, as noted above you can't use just any lighting choke on the bottom of the band so the used market is going to be kinda hit or miss.

The one outside Chicago had unlit towers and had been a loser for decades. Newsweb did a nice job rebuilding it to give the place one last chance but the daytime mostly covered Gary, Indiana and the nighttime didn't cover much of anything due to the high night limit.
It's curious that all three major suppliers (I forgot to mention LBA in my previous post) don't seem to have different model lighting chokes for different sections of the AM band. Different models for different voltages across the tower base, but nothing about frequency. In fact, all three sources show either inductance or inductive reactance for the entire band for their lighting chokes, but not separate chokes?

But irrespective of that it's going to be a crap shoot to find any lighting choke on the used market. Still, it should be worth a shot to at least look.

And the observation about the AM station with the towers for sale for a buck was as much lamentation about the slow, agonizing death of a radio service that's near and dear to my heart as it was about possible surplus lighting chokes floating around their site. I also find it curious that their towers were unlit given that the shortest was listed at being 205-feet tall, the tallest at 240-feet. At those heights all eight should have required at least a top beacon and a set of side obstruction lights unless granted a waiver. Very strange.

Re: Rebuilding a Lighting Choke

Posted: Sun Sep 18, 2016 11:27 pm
by BigRed
And here's another thought . . .

Check with some tower rigging and service companies, particularly the ones your station uses. There's a chance that one or more of them may have a choke or three sitting around the back of the shop that they may be willing to part with.

Re: Rebuilding a Lighting Choke

Posted: Mon Sep 19, 2016 9:53 pm
by Deep Thought
BigRed wrote:lamentation about the slow, agonizing death of a radio service that's near and dear to my heart as it was about possible surplus lighting chokes floating around their site.
This particular station should have been put down a couple decades ago. I'll give Fred props for trying to make it go but he still has mountains of money to piss away on projects like this from his Chicago channel 50 sale to Fox.
BigRed wrote:I also find it curious that their towers were unlit given that the shortest was listed at being 205-feet tall, the tallest at 240-feet. At those heights all eight should have required at least a top beacon and a set of side obstruction lights unless granted a waiver. Very strange.
That one's on me. I was thinking of a different site.

Re: Rebuilding a Lighting Choke

Posted: Mon Sep 26, 2016 12:31 pm
by Jim Sofonia
Well after considering all the options discussed here, he chose to have Kintronic build a replacement. $1100 vs. $3500 from Gates Air. Thanks to all of you that posted on this.

Re:UPDATE: Rebuilding a Lighting Choke

Posted: Thu Oct 20, 2016 7:20 am
by Jim Sofonia
Eric tells me he received and installed the Kintronic choke. He is pleased to report that his before and after parameters did no change. Even the mounting holes lined up making for an easy install. Thanks to all of you for helping with this problem.