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 I actually fixed something for once, rather than breaking it 
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Post I actually fixed something for once, rather than breaking it
I bought a nice old MFJ manual ATU with a differential T tuning system, I tended to get annoyed with the doublet needing retuning every 100Hz or so on a standard "T" circuit.

Anyway, it was a good price and little cosmetically rough but I knew that well before purchase as the seller did not lie to me, so I got it set up and noticed that it was intermittent upon receive as I have not transmitted into the ATU as the dummy-load construction is awaiting resistors before I can do a thing. I also noticed what appeared to be jumping and slipping off the inductor selector wheel and a general feeling of something is not right, so off with the top for a visual and whilst working the inductor dial I noticed that the inductor selection wheel was slipping off the inductors coil, jumping between two coils. At one point I could see where it has been heated up to the point of removing some of the silver coating on the coil and no doubt due to the wheel contact being intermittent.

So I thought like most black box operators that I will contact MFJ and buy a new inductor coil, then I heard that nagging voice of the other half saying "I" have spent enough on this hobby! So I thought to myself what have I got to loose and set about the strip down of the inductor, low and behold two old springs and ball bearings acting as the indents to push a bar with the inductor selection wheel was jammed at the edges. It appears as though they were fitted too tightly on the inductor shaft and jamming the purpose of the suspension design, out comes the emery paper and some cleaning up later and a re-stretch of the old springs and the inductor wheel maintains contact all the way through the tuning range and the bar can move freely up and down acting like suspension in a car so that the wheel runs true over every bump or undulations of the inductor coil. The inductor now runs smoothly throughout its range with no hesitation.

I wonder if this had been like this since it was manufactured?
Well, whatever the case may be I have now sorted it and I did not break it which is my usual outcome!

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John G Ritson CMH


Tue Aug 15, 2017 12:45 pm
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 I actually fixed something for once, rather than breaking it 
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Post Re: I actually fixed something for once, rather than breakin
From reading lots about MFJ over the years always consider it a partially completed kit when you buy and you will be ok,

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Trevor
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Tue Aug 15, 2017 1:42 pm
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 I actually fixed something for once, rather than breaking it 
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Post Re: I actually fixed something for once, rather than breakin
ei2glb wrote:
From reading lots about MFJ over the years always consider it a partially completed kit when you buy and you will be ok,

Have not had all that much from MFJ but as you mentioned that "they are like a partially completed kit" I would say that this has been case for this ATU, can't say for sure but I think someone else had attempted a fix as most of the grub screws needed replacing from being chewed up! I never had any on hand so went with the stainless bolts of the right thread fit and used my rotary tool to cut a slot so that I could use a screwdriver to tighten the parts up worked very well and much stronger.
Might have to source a selection of compression springs to replace the old ones as they will no doubt be weakened, but time will tell and it is nice to have repaired something at so little cost to myself. :hello:

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John G Ritson CMH


Tue Aug 15, 2017 2:13 pm
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