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 Post subject: National NC-100xa knob
PostPosted: Apr Mon 16, 2018 12:30 am 
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Joined: Nov Tue 18, 2008 8:34 am
Posts: 1220
Location: Hutchinson,Kansas
Trying to get the old radio repaired from the damage it got on shipping. For the life of me I cannot get the lower middle band knob off the radio. Any one have any ideas? I can remove both set screws and the center of the broken knob will spin on the shaft but will not pull off. I can remove the freq knob right above it with no problems at all. I assumed the band knob below it would come off the same way but it wont. I have had the radio on its back and almost lifting the radio up by the knob and it still wont come off. Any ideas?


Todd

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 Post subject: Re: National NC-100xa knob
PostPosted: Apr Mon 16, 2018 1:19 am 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 5346
Sometimes the knob will have spun on the shaft building up a ridge making it very difficult to remove. Try taking both set screws out and putting some oil in the holes and let it sit for awhile because sometimes this will help the sleeve in the knob slip over the ridge/burrs on the shaft.

I have run into this several times over the years. It usually results from the set screws slipping on the shaft and throwing up material that prevents the knob from sliding off. Usually the combination of oil through the empty set screw opening coupled with rotating the knob while applying outward pressure will work. I suspect you will find the shaft very chewed up when you get the knob off.

If the knob is past saving you can carefully destroy it removing the outer part from the inner sleeve and then use a cutoff wheel in a Dremel tool to split the the sleeve so it can be removed.

Rodger WQ9E


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 Post subject: Re: National NC-100xa knob
PostPosted: Apr Mon 16, 2018 7:33 pm 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1470
Location: Rochester, NY.
A couple of knobs on my NC-200 were difficult to get off the shafts due to corrosion. It had been stored in a damp environment at one time.
One knob pulled the control shaft out with it, but I was able to reassemble the control after separating the shaft from the knob while off the radio.
Any e-clips or roll pins on the shaft that would allow you to remove the knob with the shaft intact? They are easier to work on when out of the front panel and you don't want to damage the front panel if you can help it.


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 Post subject: Re: National NC-100xa knob
PostPosted: Apr Thu 19, 2018 1:17 pm 
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Joined: Jul Fri 07, 2006 6:09 pm
Posts: 1402
Location: Charlotte, NC
The usual culprit is ridges which have been dug in the control shaft from setscrews which loosened enough to allow the knob to slip on the shaft. Continuing to turn the knob digs ridges in the steel shaft which then cuts grooves in the knob's brass insert and the knob then becomes locked on the shaft. This issue is fairly easy to overcome though. Remove both setscrews and grind the end on one (or to a substitute) as flat and perpendicular as possible. reinstall the flat ended setscrew with some oil and bottom it out on the shaft snug but not tight. Rotate the knob while gradually tightening the setscrew "tool" which will burnish the raised ridges back down flat into the shaft. The knob will slip right off when you've gone far enough with it.

I keep an old unneeded knob handy which has a flattened end setscrew and I routinely use it to burnish any shaft that has setscrew tracks even if the knob came off easily.

A setscrew with hex drive will be easier to work with and control than one with a screwdriver slot.


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