Another connector gripe...

John Lohmeyer jlohmeye at ncr-mpd.FtCollinsCO.NCR.COM
Sun Sep 25 22:52:30 PDT 1994


"Tom Beach wrote:"
> 
> Agreed, also in evaluating SCSI devices with the 68 pin connector I'm
> finding that there are two cable retention schemes. One uses a latch and
> the other uses screws. As you might guess, these are totally and
> completely incompatible. If you have a cable with the latch it won't
> even mate with a connector with the screw retention. You can't even
> TEST it!!!

And only one is following the draft SPI standard, which only documents
the jackscrew retention method.

> Maybe it would be prudent for the committee to deselect this inferior
> connection scheme and quicky (did I really use quickly and committee
> in the same sentance?) move to approve a mini ribbon....
> 
> There is precedent! Anybody remember the ORIGINAL SCSI shielded connector?

Yes, I remember.  I'm the person that brought in the proposal to add the
miniature ribbon connector to SCSI-1 (because of the bent pin problems we
had with the AMPmodu connector).  To AMP's credit, they did come up with
a solution to the AMPmodu problem, but it cost more than the miniature
ribbon connector.  And the committee adopted the change in one meeting.
It can be done.

The last time the issue of bent pins came up on the Amplimite connector,
I was assured by the AMP folks that the problem had not been reported by
anyone else.  Apparently there are several more examples now.  I urge those
people with bent pins to send samples of the damaged parts to Bob Whiteman
at AMP (whiteman at cup.portal.com) along with any documentation of how
the damage occurred, if available.  It would also be extremely interesting
to find out whether the damage occurs with same vendor connectors or does
it only occur with heterogeneous vendors?

Jumping to one of the high-denity ribbon connectors would, of course,
avoid the bent pin problems, but these connectors are not necessarily
perfect either.  Ribbon contacts do not handle vibration as well as the
tab-and-receptical style contact.  I think it is prudent to do a little
failure analysis first.

John

-- 
John Lohmeyer                      E-Mail:  John.Lohmeyer at FtCollinsCO.NCR.COM
NCR Microelectronics                Voice:  719-573-3362
1635 Aeroplaza Dr.                    Fax:  719-597-8225
Colo Spgs, CO 80916              SCSI BBS:  719-574-0424 300--14400 baud




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