What will fail if the U piece falls out?  Will the resulting cost of
resolving that issue(s) offset the cost of buying (50) new custom molded
connectors?  Why cannot the jumper be applied elsewhere in the system?
Lastly, why not a "dongle" which would be just two back-to-back
connectors, with the required jumper in place?

I can see the need to reduce waste (cost) and to make it not require yet
another item--but it seems like a failure point that might be worse of a
headache in the field if it ever occurred, than if the solution was
applied elsewhere.

Shawn Upton, KB1CKT
Test Engineer
Allegro MicroSystems, Inc
[log in to unmask]
603.626.2429/fax: 603.641.5336

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl VanWormer
Sent: Wednesday, August 19, 2009 11:38 AM
To: [log in to unmask]
Subject: [TN] Guitar string shorting jumper

We have need to "permanently" connect two adjacent pins of a female DB-9
connector that has a molded housing, so we can't get at the back side of
the connector for a properly soldered connection.  The first suggestion
was an adapter (male and female connectors, PC board, and insulating
housing or heat-shrink cover).  For the planned quantity of 50 units,
this design effort seemed like a bit of overkill, even ignoring the size
of the ugly protrusion of this adapter out the back of the product.

An alternative is being considered that needs some "fatherly guidance"
from the collective TechNet intelligence:
A short length of .008" steel wire guitar string with a U-bend to span
the two female terminals could be inserted into the proper terminals of
the female DB-9 connector.  If the two legs were bent back on
themselves, forming barbs, the shorting jumper could be inserted into
the DB-9, with the barbs performing a lock-in function to hold the
shorting jumper in place.  A quick test of a bent-up sample indicates
that this approach seems to work well, with only minimal distortion of
the female sockets.  The final product is expected to have only a few
insertion/removal cycles in its lifetime.

The questions to this group are:  
1.  How crazy am I to suggest this solution?
2.  Should I consider Gold plating (or something else) to increase
reliability?

Thanks,
Carl

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