[R-390] Mech filter REPAIR Lankford Trial?

[Dave or Debbie Metz]

A question for this esteemed group:  I seem to remember that in the 
HSN newsletter a few years ago  Dr. Dallas Lankford did a test of 
using a  current filter available from one of the various electronic 
suppliers.  As I recall, it wasn't perfect but was 
relatively  inexpensive. Given the previously noted failures of the 
existing filters, the options down the road would seem to indicate 
either a  remanufacture process, or a good substitution.  Has 
anyone  subsequently tried Dr Lankford's suggestion and could they 
give us a blow by blow account?  I have to sort of believe we need to 
explore a reasonable cost substitution for a component that cannot 
directly be substituted. $600 of filters in a $600--$800 radio seems 
a bit questionable.
Thanks
dave


At 10:44 AM 6/2/2007, Craig C. Heaton wrote:
>Tim & All,
>
>Someone with the correct tooling could make this wish happen. From the two
>websites recently shown on this e-mail reflector, it seems there are
>different styles of mechanical filters.
>
>The only one I've disassembled, the interior is one unit and has to be
>removed as one piece. Then it could be farther taken apart. Trying to pull
>only one end off would of destroyed the filter.
>
>The coil is the sticky wicket on this one. I'll guess the potting substance
>covering the #38 enameled copper wire seems to be the same material as the
>spool!! Once again a guess, it looks and behaves like delrin. This is the
>same material that was used for the gears in the HP 8640B sig-gens. It
>shrinks with age, snap goes the wire!