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MFJ-986 Antenna Tuner

Created by on 2021-09-10

In 2019 I purchased a brand new MFJ 986 antenna tuner. When I received it and as I was removing from the box, and you could hear a part rolling around in it and then inside the shipping box there was a one-inch bolt. I called them and they sent me another one and it worked great for a year.

 

Then a year later it started to act erratic, so I opened it up and it was full of metal screw particles. I took a brush and compressed air and cleaned it out.

 

Next, I took a can of DeoxIT D-Series D5 electronic cleaner and sprayed all the connections, also the two gears for the Inductance knob were out of aligned so I corrected them also. Boy what a difference all around now. I am very happy with this tuner again and it even adjust a LOT smoother now.

 

Hopefully this will help others who may be having this problem!

 

VE3CUI2021-09-12
MFJ-986 Antenna Tuner
I'm not intimately acquainted with the MFJ-986 tuner, but if it has a roller inductor in it, try this trick that veteran General Motors toolroom techs used to use on all of their electro-mechanical devices to ensure smooth, trouble-free operation: apply just a couple of dabs of ordinary CASTOR OIL onto those components that a contact roller(s) might slide across as the inductance is varied.

PERIOD.

I do this on my home-brew transmatch, as well as my home-brew linear amplifier --- both of which employ large air variable inductors --- & the result is smooth-as-silk reliable operation, for years.

I also apply just a dab of castor oil onto the bearings of variable capacitors here, as well --- gets rid of any stickiness, yet does not affect-alter the capacitance in any adverse way.

Just REMEMBER, though: "A LITTLE DAB'LL DO YA...!!!"