[ARC5] Etching Crystals and WHINK Revisited - contact resistance.

[Dennis Monticelli]

Regarding broken bonds on FT-241 blanks:

Go to Radio Shack and buy the conductive glue.  I think it runs about $5
for a small tube that will go a long way.  Put a small amount over the
broken connection.  If the surface of the plating or the surface of the
wire bond is badly corroded the glue may not form a full conductive path.
You may be able to remove the surface corrosion with the proper choice of
chemical.

Note that because the glue will increase the mass, the freq may drop a
little.  In fact, the thickness of plating is sometimes used in modern
crystals to tweak the freq.

I can't think of any other repair techique for that problem. It is
analogous to the wire bond lifting on the pad of an IC, something of which
I am very familiar.

Dennis AE6C

On Wed, Nov 5, 2014 at 7:41 AM, Kenneth G. Gordon <kgordon2006 at frontier.com>
wrote:

> On 5 Nov 2014 at 0:49, Mike Everette via ARC5 wrote:
>
> > With the FT-241, the leads from the holder pins are soldered or welded to
> > electrodes attached to the quartz.
>
> The electrodes are plated onto the quartz, which is usually circular, not
> rectangular like in FT-243s. If one attempted to etch those, the plating
> would
> come off and there would be no way that **I** know of to reattach the
> electrode to the quartz.
>
> >  I've seen many of these wherein the welds
> > (?) have broken.  No idea how to fix this.  Out of a box full of these
> > crystals which were given to me maybe 30 years ago, about half of them
> are bad.
>
> I have quite a number of those LF FT-241s which were used in the SCR-608.
> There is no way that I know of to change their frequency.
>
> > The FT-243s I have opened up have responded rather well to cleaning the
> brass
> > plates (BE CAREFUL), and/or washing the quartz.  I've been able to repair
> > several holders with brass plates broken away from the pins.  Not all,
> > though.
>
> Yes. Some simply will no longer work no matter what we do to them.
>
> Ken W7EKB
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