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WA3DSP
12-29-2012, 03:39 AM
One of my winter projects will be rebuilding and updating a Heath SB-200 amplifier. Unfortunately the plate RF choke is physically broken and not repairable. I have not been able to find a commercial choke that would be physically and electrically compatible. I suppose I could wind a new choke. I have a suitable piece of Teflon. The original choke was close wound, no breaks, and measured about 50uh. I am sure Heath did some engineering of this choke but other similar amps seem to have multi-segmented chokes with much higher inductances , 200 uh is common.

Any ideas would be appreciated? If anyone has replaced this choke with a commercial value or rewound it let me know your experience.

Doug, WA3DSP

K1ZJH
12-29-2012, 03:50 AM
Contact Lou: http://qroking.com/

He does 6 meter conversions, and he should have some usable plate chokes on hand from SB-200 amps.

Multi-segmented windings breakup series resonances--they became more popular when amps started to include the WARC bands.

Pete

KO6WB
12-29-2012, 04:44 AM
Or you could use the one Ameritron has; http://www.mfjenterprises.com/Product.php?productid=10-15197. It's 20 buck and 225uh. It'll easily handle the voltage and the current.
You can rewind you own and the older ARRL Handbooks usually have that information in them. It doesn't have to be exactly the same but it would be nice if you could get close.
These guys did use the Ameritron plate choke as well as doing some other very interesting (strange?) things to an SB-200. Here; http://www.kcdxclub.com/AC0C%20SB200%20Sleeper-v3a.pdf.
Have fun
73
Gary

WA3DSP
12-29-2012, 05:07 AM
I sent Lou an email. The Ameritron (RF Parts) choke is way too big to fit in the RF compartment of the SB200 with the 572's. If anyone has shoehorned it in let me know. The article is interesting and I will add it to my reference material but I think they used the RF parts choke with the new Russian tubes they installed. That choke is about 1.5 times more in diameter and about 6" vs. 3.75" tall for the original choke.

KO6WB
12-29-2012, 12:54 PM
I sent Lou an email. The Ameritron (RF Parts) choke is way too big to fit in the RF compartment of the SB200 with the 572's. If anyone has shoehorned it in let me know. The article is interesting and I will add it to my reference material but I think they used the RF parts choke with the new Russian tubes they installed. That choke is about 1.5 times more in diameter and about 6" vs. 3.75" tall for the original choke.
Not sure they actually did or not but if you look at the photos of the SB-200 there are some that show the Ameritron choke with 572B's. They may have done it or found out the GI7B's where a better idea.
Hope this helps
73
Gary

K1ZJH
12-29-2012, 03:51 PM
Not sure they actually did or not but if you look at the photos of the SB-200 there are some that show the Ameritron choke with 572B's. They may have done it or found out the GI7B's where a better idea.
Hope this helps
73
Gary

I used the MFJ RF choke in my SB-220 as it was designed for 160 Meter and WARC band coverage... it was a tight fit, but my entire RF deck was redesigned to accomodate the changes.

Pete

WA3DSP
12-29-2012, 05:23 PM
Pete, Did you document, take pictures, of your mod? I would be interested in seeing.

73 Doug

AF6LJ
12-29-2012, 05:26 PM
Pete, Did you document, take pictures, of your mod? I would be interested in seeing.

73 Doug

Post number 8 in this thread, very nice job...
http://forums.qrz.com/showthread.php?372651-SB-220-Find&p=2725590#post2725590

(http://forums.qrz.com/showthread.php?372651-SB-220-Find&p=2725590#post2725590)

WA3DSP
12-29-2012, 06:24 PM
OK thanks, but that is a SB220. I am talking about a SB200. Two different animals! There is less room around the tubes in the 200.

AF6LJ
12-29-2012, 07:21 PM
OK thanks, but that is a SB220. I am talking about a SB200. Two different animals! There is less room around the tubes in the 200.

There is no way that choke is going to fit in your SB-200.
Every once and a while those chokes show up on E-Bay.

N3JBH
12-30-2012, 01:10 AM
Are them chokes that hard to find ?

WA3DSP
12-30-2012, 01:35 AM
I wonder if anyone has used iron core material in RF chokes? This article -

http://kk5dr.com/chokes.htm

Seems to indicate that it works well but I am sure there is another side to the story. If it works as well as he claims I am sure you would see them in commercial products.

There is some discussion out there disputing KK5DR's claims but it appears they tried to use ferrite which he points out NOT to use in his article.

K1ZJH
12-31-2012, 04:25 PM
Are them chokes that hard to find ?

Lots of those amps being parted out... and guys like Lou and Carl, KM1H are doing 6 meter conversions. Finding clean, used choke shouldn't be too hard, or expensive.

Pete

N3JBH
12-31-2012, 05:09 PM
Thats what i thought, I know i have at least one laying around here from a SB 200. Not sure why i am hanging on to it but heck you never know when ya might need one.

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