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Author Topic: jonson matchbox  (Read 1339 times)
N2JXN
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Posts: 189




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« on: February 06, 2008, 02:25:28 PM »

Hello and thanks for taking the time to read this I have recently come into possesion of a johnson matchbox. upon opening it up to look at the condition I found that everything looks good except for the coil. It had plastic spacers which have broken into small pieces. Is there somthing or a way to repair/replace this so as to brin them back to the right spacing. Thanks
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KA5N
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« Reply #1 on: February 06, 2008, 06:34:01 PM »

The coils in E.F. Johnson matchboxes are were built with the windings embedded in plastic strips.  Probably the strips have come apart due to aging of the plastic (becomes crazed as it gets old).  The coils were heated and they melted into the strips. Unfortunately the pitch of the coil is not constant and although the same style coils are available, they are made with a constant pitch.  You might be able (if you have a steady hand) to hot glue plastic strips to the coils.  If you have the kilowatt version such effort might be worthwhile, but the 275 watt job is not worth nearly as much.  The other possiblity is to get another junker and make one good unit out of the parts of the two.
Good Luck Allen
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KE3WD
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« Reply #2 on: February 07, 2008, 09:34:04 AM »

 
The hot glue method is faster, find the highest temperature hot glue rods you can, though.  This can be done with the coil in situ with a little thought.  Works fine for me.  

Don't try to remove the old plastic that is stuck to the coil.  Okay to pull out any that is very loose or lying on the chassis, though, of course.  


KE3WD
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N2JXN
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« Reply #3 on: February 07, 2008, 03:01:17 PM »

Thanks for the info. Is there a site that shows the internal look of the unit. Would like to compare it to the one I have as it seams the prier owner tried to make it in the the killowatt version. If you compare the one I have with the schematic it looks that way. Being I got it for nothing I would like to try and see if I can restore it enought to play around with.

Also is there a site with info about this.

Thanks again for all the help and support
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WA2FNS
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« Reply #4 on: February 08, 2008, 07:13:09 AM »

Hi,
   Have pictures of the 250 watt matchbox that I took for others.Send your email address, will forward.They are big pix, about 650 kb.......John
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N2JXN
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« Reply #5 on: February 08, 2008, 09:04:56 AM »

Thanks John. The E-mail address is Chris54@gmail.com.
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KL7AJ
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« Reply #6 on: February 08, 2008, 01:58:45 PM »

Yip....I did the hot glue on mine....works like a champ..

eric
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N2JXN
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« Reply #7 on: February 09, 2008, 02:41:30 PM »

Thanks for all the input. Ian looking for the porcelain insulators for the matchbox does anone have any ideas as to where to get them
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WD4HXG
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« Reply #8 on: February 27, 2008, 03:53:45 PM »

Hello John

If you have the old insulators you can glue them back together. Most auto parts houses have a thick form of Superglue which works well in this application.

Trying to buy new insulators is troublesome. You might try Cambion. Last time I checked about a year ago they still carried some insulators. Also try the surplus stores. While in California on business a few years back I found a box of old insulators priced at fifty cents each. ALso check e-Bay. Every once in a while someone will part out a Matchbox.

As for the plastic strips my solution was to cut strips of 0.25 inch thick plexiglass slightly longer than the coil. There is a kit called Plas-ti-pair, a two part powder and solvent. I mix up a batch of plas-ti-pair and apply a bead to the edge of the plexiglass strip. Then I place it on the inisde of the coil.. It sets quickly and within five minutes I apply another batch along the new plexiglass on the outside of the coil.

A few ops say the 250 watt model of the Matchbox is not worth the effort. I disagree as no house manufactures a  comparable box at an attractive price these days other than MFJ. MFJ's price is right but the Matchbox is mechanically superior in my opinion.

YMMV

73

Chuck
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