[R-390] Mechanical filter postmortem

[Jordan]

Yes the foam sheet I have used is a form of closed cell foam....I don't know how
well it would hold up if you were resoldering the filter case, the Yaesu filters
are not soldered near as much a the Collins filters are, but then the foam was
used when they were both originally soldered, so....?    73 de Jordan...

John Kolb wrote:

> On Mon, 8 Apr 2002, Barry Hauser wrote:
>
> > You wrote
> > > I have repaired several Mechanical filters in Yaesu gear, but they open a
> > > lot easier than the Collins filters do... In the Yaesu filters, it is
> > > usually migration and decay of the 'foam' padding that causes an increase
> > > in loss through the filters... Yes I have had to resolder a couple of the
> > > pick-up coil leads also.. 73 de Jordan...
> > >
> >
> > Did you replace the foam stuffing?  If so, with what?  Is it necessary?
> >
>
> When I repaired a couple  of Kokusai filters, I used loose cotton
> from the filler in a medicine bottle. Someone recently (Barry?)
> reported using a sheet of closed cell foam, which sounds like
> a better idea to me.
>
> Comments on Buzz's postmortum - GREAT!
>
> That wire he pictures "sticking up in the middle" that's
> the magnetostrictive element - if that breaks off, writeoff
> the filter.
>
> Judging from my experience with the Kokusai filters, yes
> the polyfoam in the Collins filter could get on the disk
> elements and cause them to become more lossy. If the filter
> bias permanent magnets became weaker, that could also be
> the cause of a weak filter.
>
> I've repaired a small number of Collins filters with open
> coils - if the wire breaks at the terminals, it's an easy
> repair - once found a  filter with a terminal that had never
> been soldered. With care, a wire broken halfway between
> the filter coil and the  terminal can be spliced. If the wire
> breaks at the coil on the outside of the winding a little
> can be unwound and extension soldered on.
> If at the end of the body but coming from the coil pi winding
> from the other end of the coil, It can be losened from the
> glue blob and extended. If the broken lead is from the inside
> of the coil - the part next to the core, the coil is toast.
> I have, however, done a coil transplant from another filter.
>
> After spending lots of time holding a 250 watt iron trying
> to unsolder the case on D/E case or the small V case filters,
> I gave up and just cut off the filter end with a mototool
> with cutoff wheel. Save the end piece and glue  it back
> on with hotmelt glue.
>
> > Just a sec... YO!  BACK THAT TRUCK FULL 'O FILTERS IN RIGHT HEEEUH!  THAT'S
> > RIGHT, A LITTLE MORE, COME BACK .. COME BACK ... WHOOOAAAA!  UNLOAD 'EM
> > BOYS!.
> >
> Actually I do have a box of bad filters waiting for the time
> I can get back to trying to repair more of them - have never
> been willing to sell them as I've afraid I might end up buying
> one of them back at the swap meet labeled good  :) All the open
> coil ones have been worked on, sucessfully or not. Remaining
> 40 or so have more serious problems. No R390 filters
> among them however.
>
> Commercial plug- e-mail me if you want a copy of my list
> of filters for sale.
>
> John