MFJ-989 lubrication

AK9R

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I've acquired a used MFJ-989C roller inductor tuner.

The inductor knob seems to be a little stiff and inconsistent to turn. I'm wondering if it would help to sparingly lubricate the innards. There are two points of consideration: the plastic gear train for the turns counter and the bearings at each end of the inductor frame. The roller seems to be turning freely, so I'm not worried about it. What lube to use? WD-40? White lithium grease? Teflon spray lube?

Thank you.
 

mmckenna

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My concern with WD-40 is it tends to have a solvent action that will often flush lubrication out. It does seem to leave behind a bit of oil.
Other issue I noticed was that it sometimes damages plastic.

Lithium grease is what's often recommended for plastic gears. I have a small tube I used on the gears in my garage door opener, hasn't fallen apart, yet.
 

jonwienke

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DuPont chain saver is a Teflon/wax lube that has proved safe on every plastic I've tried it on. And It's a good gun lube, too!
 

K4EET

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@W9BU, I also have the MFJ-989C 3 kW Series-Roller Inductor MFJ Versa Tuner V. That is a great tuner and you will be able to tune everything from a wet noodle up. It is very versatile. You might also want to contact MFJ Tech Support at (662) 323-0549 and see what they would recommend that you do/use. 73, Dave K4EET
 

krokus

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WD-40 is not a lubricant. It has a small amount of lubricity as a byproduct. Seeing people use it in place of a lubricant, especially a penetrating oil, grinds me. (Like mmckenna and magnetic mounts in place of the drilled hole.)
 

mmckenna

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grinds me.
Indeed. WD-40 and Duct Tape are not proper 'fixes'. I'm ashamed to own both, but they do have their place. If I use WD-40, I always follow up with a proper lubricant.
And I don't think I've used duct tape in years (gaffers tape is much more useful…).
 

mmckenna

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Correction... That should be DUCK tape from what I've heard... :ROFLMAO: :ROFLMAO: :ROFLMAO:
It goes both ways...

Duct Tape used to seal ventilation ducts. I've never seen a ventilated duck.
but some say it originated as "Duck tape" as it was used to seal ammunition boxes in WW2, as in "water off a ducks back".

To me, either one works, and when you tell someone you want duct tape, they likely are not hearing the difference between the K and the T.

But, yeah. If you think Duct/Duck tape is wonderful stuff, you need to get a big ol' roll of gaffers tape and really live the high life. Once you use that stuff, you never go back.


And I recall my uncle talking about when WD-40 came out, people using it for lubing guns. The solvent would get into the cartridges and cause them to fail.
And an IC guy in the navy, that used it on the sound powered phone jacks, only to discover it destroyed them. Most ships don't carry enough spare SPP jacks to fix them all.


For the record, I do own two mag mounts, one with a UHF connector and one with a mini-UHF connector. Both used for testing only, short duration use.
 

K4EET

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@mmckenna, in reality, I said that jokingly which was the reason for the three ROFL's. Sorry, my friend. But I did learn something. I've never heard that story about the WWII ammo cans. Wow!

Have you heard that WD-40 got its name because it was developed to be a Water Displacement spray (hence WD) and it was the 40th attempt of chemical mixtures before they got it right as they wanted?

Again, sorry for my attempt at a joke on the Duct Tape.
 

mmckenna

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Again, sorry for my attempt at a joke on the Duct Tape.
Not a problem, I knew you were joking. Just went off on a tangent since I'd talked about it with someone at work recently. She felt that WD-40 and Duct Tape were a good solution to many problems. I prefer arc welding and smoke wrenches, myself.

Actually, I find the history of some product names kind of fascinating.
 

AK9R

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Speaking of going off on tangents... :cool:

I put a couple dabs of white lithium grease on the turns counter gears and then wiped off the excess.

And, I sprayed a couple spritzes of dry teflon lube into the bearings at either end of the roller inductor shaft. I put no lube on the roller wheel.

I also sprayed a couple spritzes of Deoxit D5 on the switch contacts and worked the switch back and forth several times.

Subjectively, the inductor knob seems to turn easier. With some effort, I can turn the inductor knob using just the finger hole on the knob. Definitely doesn't turn as easy as the rotary encoder tuning knobs on my radios, but it seems to turn easier than when I first got the tuner.

For those wondering, this tuner uses what I understand is called a "slinky" style roller inductor. There's a coil of stiff wire that is held in place at 0, 90, 180, and 270 degrees around the coil by what looks like circuit board material that has been notched to maintain the spacing of the coil. There's a shaft running through the axis of the coil with a roller attached to an arm so that the roller rolls along the inside of the coil. The coil does not move or deform as the roller moves through it.

Granted, being an MFJ product, it's built down to a price. MFJ might claim that it's a "3 kW tuner", but I know that I will never run that much power through it. I tried it yesterday evening with my 80-40-20 fan dipole and quickly got a tuning solution on all three bands using 100 watts on RTTY.

Finally, in typical MFJ fashion, the tuner had a rattle when I first got it. I took the cover off and found a loose screw. Upon further examination, I determined that the screw came from one of the brackets holding the inductor to the chassis. The nut for the other end of the screw was nowhere to be found. I obtained a replacement nut and reinstalled the screw. I snugged up the other fasteners on the inductor while I was at it.
 
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