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Old 24th Jun 2018, 10:40 am   #1
NickG0HIK
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Default MCR-1 Aerial Trimmer

I got around to trying to sort out the Aerial trimmer on my MCR-1. The shaft of the trimmer was very loose and the vanes touched each other.
Upon inspection the radio must have suffered a bang at some time (maybe other than in the 1940's ), as a part of the knob was loose inside the set. The loose shaft was caused by the sprung earth connection being distorted.

I tried to sort things out and with my hamfistedness have only made things worse,the vanes of the rotor and stator have now parted company with the shafts they were crimped on to.

I feel the only action is to replace the trimmer capacitor now.

I've not seen these trimmer capacitors, before any ideas what other equipment used them, to look out for.

Any ideas how to get the shaft nut off, the insulating washer has done a fine job of locking the nut on and due to other components in the area I cannot get a spanner on it.

The Cap is 15pf, the shaft is 4mm diameter and 30mm long.
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Old 24th Jun 2018, 10:42 am   #2
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Default Re: MCR-1 Aerial Trimmer

Use a long reach thin walled socket on the nut?
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Old 24th Jun 2018, 10:48 am   #3
NickG0HIK
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Default Re: MCR-1 Aerial Trimmer

Thanks, yes, sound obvious, but once you see the set, that is not possible without removing a "PCB" that the shaft goes through.
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Old 24th Jun 2018, 11:07 am   #4
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Default Re: MCR-1 Aerial Trimmer

If all else fails, plus gas or whatever then soldering iron heat on the nut as best as possible then use an old small screw driver with a sharp blade (to use like a small mini chisel) sharp tap on the nut edge anticlockwise just before a hex point, once seal's broken use longnose pliers in the tenth of a turn at a time shuffle mode, should come off ok. Done a few, a bit like cracking large nut/screw interface with a cold chisel on old vehicles etc.

Lawrence.
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Old 24th Jun 2018, 5:45 pm   #5
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Default Re: MCR-1 Aerial Trimmer

Quote:
Originally Posted by NickG0HIK View Post
Any ideas how to get the shaft nut off, the insulating washer has done a fine job of locking the nut on and due to other components in the area I cannot get a spanner on it.
In situations like this where there is insufficient room for a conventional open ended spanner I usually find that an open ended ring spanner will do the job as long as the split is wide enough to go over the shaft. You really need a proper castellated one as per the photo below (they are both 5/16") not just one with six flats. A search for 'open ended ring spanner' produces lots of hits.

Mike
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Old 24th Jun 2018, 7:31 pm   #6
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Default Re: MCR-1 Aerial Trimmer

A 'box spanner' [which is basically a tube with the end formed into a shape to fit the nut] is what you want here.
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Old 24th Jun 2018, 9:54 pm   #7
NickG0HIK
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Default Re: MCR-1 Aerial Trimmer

Thanks for the input guys, I particularly like the idea of an open ring spanner. I'll see if I can source the correct part for the job.

Nick
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Old 2nd Jul 2018, 1:09 pm   #8
NickG0HIK
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Default Re: MCR-1 Aerial Trimmer

Quote:
Originally Posted by Dual Standard View Post
In situations like this where there is insufficient room for a conventional open ended spanner I usually find that an open ended ring spanner will do the job as long as the split is wide enough to go over the shaft. You really need a proper castellated one as per the photo below (they are both 5/16") not just one with six flats. A search for 'open ended ring spanner' produces lots of hits.
I could not find an open end ring spanner easily, but Screwfix stock a 1/2" AF combination spanner. A little bit of work with the Dremel turned it into an open ring though.
Nothing is easy with this project though, the mounting boss on the trimmer just span around and the lock nut would not come off.
I removed the capacitor shaft and fitted a screw extractor in the hole left and finally managed to get it all removed.

Now to see if my local metal turning hobbyist can devise a way of joining the 4mm shaft to the 6mm one.

Nick
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Old 18th Jul 2018, 7:46 pm   #9
NickG0HIK
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Default Re: MCR-1 Aerial Trimmer

All working well now, I got a model maker to turn a 6mm shaft extender down to 4mm to take the original knob.
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