[R-390] 4 kc filter

Wed, 24 Jul 2002 15:16:08 -0600

I have had to rewire a bobbin in Kokusai filter as it had broken.. I simply unwound
3 turns, out of the hundred or so turns on the bobbin, clean the end , and solder it
back on.. worked like a charm...
The trick with some of the Collins filters is removing the filter assembly and the
rubber fittings without causing more damage .... 73 de Jordan...

John Kolb wrote:

> On Wed, 24 Jul 2002, Norman Ryan wrote:
>
> > Hello, Les and crew,
> >
> > True enough.  But I wonder why that is.
> >
> > Is it disintegrating plastic foam gumming up the works or causing the
> > resonator to touch the shell?
> >
> > While I'm here, anyone know the enameled wire size on the bobbins?  How
> > many feet of wire for 50 Ohms DC resistance?  I've got a couple of duds
> > I'd like to try and revive some time.
> >
> Very, very fine, much smaller than 30 ga. Probably varies with the
> filter, smaller with the newer, smaller filters.
>
> > Other than resoldering a broken lead inside, has anyone successfully
> > revived one of these either by rewinding the bobbin or replacing plastic
> > foam?
> >
> I've restored a couple of Kokusai filters by replacing the foam
> with cotton - don't recall seeing any foam in Collins filters,
> only rubber fittings. Haven't been inside the type "N" filters
> used for the R-390A, so don't know how they are supported.
>
> I haven't rewound a bobbin, but have transplatted a bobbin from
> a different filter for a repair.
>
> John  KK6IL
>
> > 73 de Norman KG4SWM
> >
> >
> > [email protected] wrote:
> > > They might be good "now', but the 4 kc filter is/was the most used filter on
> > > the R-390A. They will only vibrate a certain number of times before they go
> > > kaput! And, that time has approached judging from the failure rates being
> > > reported now.
> > >
> > > Les
> > _______________________________________________
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> >
>
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