[R-390] Mechanical Filter Repair

[Dan Merz]

Hi,  in general the only reason to use 42 vs a bigger size is whether or not 
you can get the same number of turns on the bobbin with the larger wire as 
was on there with the smaller wire.  If the original wire filled the bobbin, 
then probably best to use the same size wire. The other consideration in 
choosing wire is the type of coating.  I believe "formvar" will be hard to 
remove for soldering and abrasion is the most easily done method for the 
formvar wire I've used.   There's probably a solvent that will work but I 
never found one that acted very quickly.  I've gone to using the later PE 
coated (I think that's the plastic type) type wire that allows the coating 
to remove itself under the soldering iron.  With #42 you have to be careful 
if scraping the wire but it can be done.  I've bought all the wire I have on 
eBay but it seems the price can vary a lot.  I like the 1 lb rolls;  the 
wire unspools nicely off the end;  as the roll gets down it tends to hang a 
bit at times and can break easily at that point.  Don't try unspooling it by 
rotating the roll unless you're only after a small amount of wire,    Dan.
----- Original Message ----- 
From: <Flowertime01 at wmconnect.com>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, June 13, 2007 1:46 PM
Subject: Re: [R-390] Mechanical Filter Repair


>
>
> The finest size I have is 38 gauge but the filter requires 42 gauge .0025 
> mil.
>
> Keith,
>
> You do not have to use exact wire. It must be small enough to fit.
> I do not know how close 38 is to 42 but Its likely good enough.
>
> One place to find small wire is 110 volt relays and solenoid valve coils 
> in
> washing machines. That's a scrounging venture. Auto relays are another 
> place.
>
> Wind the critter back with what you have and give it a try.
> Likely you do not have enough RF isolation in the shack to let you detect 
> the
> difference in the rebuilt filters performance.
>
> Roger AI4NI
>
>   </HTML>
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