[Boatanchors] Roller inductor cleaning

[rrkrr]

Ian,
Silver is relatively resistant to oxidation in air, but readily forms 
compounds with any sulfur impurities in air.  The tarnish seen on silver 
inductors is usually Silver Sulfide (AgS).  The thickness of the tarnish 
layer increases over time if left to itself, and although AgS is 
conductive, it is not as conductive as Silver, so it starts to interfere 
with connections after a while.  Fortunately, AgS is rather soft and 
wipes off with friction rather easily.  Removal of thick layers can be 
facilitated with a solution of baking soda in water.  After removing the 
thicker layers, your roller inductors will stay clean enough if you keep 
the roller pressure tight and operate the rollers often enough to keep 
the contact surface wiped clean.

Bob
WB4TGG

Ian Wilson wrote:
> I'm putting the HF section of a GO-9 on the air. Last night was the first
> time that I've had a chance to do any testing on the PA section (the MO and
> IA appear to be working well so far).
>
> While tuning the PA (with *very* reduced voltage on the plate), it became
> obvious that the (two) roller inductors are making intermittent contact. I
> have used similar techniques to clean them that have worked successfully on
> ARC-5 roller inductors - i.e. a toothbrush with a slurry of BarKeeper's
> Friend, followed by wiping off any residue with damp paper towels, and
> drying well. The inductor wires are now a nice clear silver.
>
> Have also cleaned the slider bars and the roller wheels, but these are still
> somewhat discolored. These appear not to be silvered, rather some sort of
> brass or other copper alloy. Suggestions for how best to clean these?
>
> I don't think I can dismantle the inductors, so have to work with what I can
> see of them.
>
> When tuning, I could see some arcing between the roller wheel and the
> inductor itself, so it may be that most of the problem lies with the wheel.
>
> The spring mechanism that applies pressure to hold the wheel to the inductor
> appears to be weak on the PA roller inductor. The springs may have weakened
> over the years. Ideas for how to stiffen this up would be welcome.
>
> Thanks for any help.
>
> 73, ian K3IMW
>
>
>
>
> _______________________________________________
> Boatanchors mailing list
> Boatanchors at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/boatanchors
> ** List Administrator - Duane Fischer, W8DBF/W9WZE **   
> ** For Assistance: dfischer at usol.com **         
> $$ For vintage radio info, see the HCI web site $$      
> http://www.w9wze.org    
>
>
>