[TowerTalk] Roller Inductors

[zl1aih at ihug.co.nz]

>> I recently returned to the air after an eight year absence.  The
>> roller inductors in my Nye MB-V-A and my Ten Tec 4229 antenna tuners
>> have corroded and are intermittent.  I have squirted contact cleaner
>> on the coils and rollers and run the rollers back and forth with no

>My *guess* would be the coil surface is OK. That oxidation is
conductive.
Roller?  One drop of WD-40, or PB Blaster. Don't spray and don't get
on 
anything else.
However there is a wiper for the coil itself (not the roller) that
might 
need attention. I'd try a lubricating contact cleaner on that if need
be.

The problem with lubricants is not their insulating qualities, but
rather 
their great ability to catch and hold dust which creates an
abrasive.

OTOH my MFJ989Cs (the one in the den gets far more use than the one in
the 
shop) will start to complain if the roller isn't "exercised" every few
months although I've never had any problems with them in actual use. 
When I 
hear lots of static in the receiver while moving the inductor I know
it's 
time to run it end-to-end a few times.>


>> improvement.  Does anyone have any suggestions?
>> 73, Hank, W6SX
>> Mammoth Lakes, California
>
>
>
> The RCA manual for their AT3 transmitter (WW2) recommended a mixture of
> anhydrous lanolin and carbon tetrachloride as a lubricant for the roller
> carriages.
> I still have some anhydrous lanolin but carbon tet is no longer available 
> in
> NZ.
>
> My local chemist ('drugstore' in US) sold me a small bottle of
> trichloroethylene after
> strict examination and sure information from the RCA manual revealed that 
> my
>
> intentions were entirely legal.
>

>What's illegal about tri-chlor? Other than being a proven carceogenic,
it's 
a whale of a good degreaser. It's also directly absorbed through the
skin.> 

My dispensing chemist seemed to think that there is some NZ Government 
regulation concerning tri-chor - he insisted on photocopying the page from my RCA 
AT3 manual.   I didn't ask him why RCA would specify a mixture of a de-greaser 
and grease - chemistry was never my strong subject anyway.

The mixture works well on the AT3 roller inductor - 26 microHenry, 5" diameter flat-
wound 1/2" by 1/8" copper bar, double rollers on a 3/8" carriage - no static in the 
receiver during rapid band-change, and the turns-counter crank is easy, if the 
operator (in his youth) has owned a Ford Model A.
    
The inductor and the vehicle have much in common - only 10 years between 
design, and both almost indestructible.<G>

73, Ken ZL1AIH