[R-390] 4 kc filter

Wed, 24 Jul 2002 12:43:53 -0700 (PDT)

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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