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I have a piece of equipment with about a dozen 3M 20-pin SCSI D-sub connectors, which are used for servo rotary encoder cables.

Here is a picture of what the cable side looks like. enter image description here
3M PN: 10120-3000 (female PN: 10220-XXX)

The trouble I'm having with these connectors is that they are extremely unreliable. If I just touch them, several of the pins will lose continuity, and the equipment will fault.

I have verified this repeatedly. I even ordered 4 sets of connectors from Digi-Key (4 male and 4 female), and they too show the exact same behavior. If I mate any two connectors, two or three of the pins will measure 'open' using a DMM (no wires in this test, just the connectors). And if I re-mate them, the open will move to another set of pins. Pushing them together harder seems to make it worse. It takes many tries before I can get continuity on all 20 pins, and usually it's after wiggling the connectors and then pulling them apart about 1 mm. And If I just barely touch the either connector, I get an open again.

It seems that a lot of servo motor drivers use these connectors. But I'm shocked at how unreliable they are.

Has anyone seen this before? Is this a known issue? Is there anything I'm doing wrong? Or is there anything I could do to make this go away?

The connectors on the equipment I'm using are maybe 10 years old, and the ones I ordered from Digi-key are all brand new, and they all show the exact same flaky behavior. So, it's not a case of a bad batch or anything like that.

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  • \$\begingroup\$ Talk to 3M! It's their connectors! You are their customer, you can demand answers. I don't think you're doing anything wrong, but you'd have to show also clear pictures of how you've terminated those connectors. \$\endgroup\$ Apr 8, 2023 at 23:49
  • \$\begingroup\$ try tightening all the way, and then backing up screws one turn \$\endgroup\$
    – jsotola
    Apr 8, 2023 at 23:52
  • \$\begingroup\$ @jsotola, this is basically what I am doing, and it does produce the best results, although, it still takes multiple tries before the connection is good again. \$\endgroup\$
    – njs
    Apr 9, 2023 at 1:31
  • \$\begingroup\$ @Kubahasn'tforgottenMonica, I can replicate the problem with just two brand new connectors and a digital multi meter: no termination required to show that these things are completely flaky. Contacting 3M will probably be my next step, but I'm reluctant. I've contacted manufacturers in the past, only to be ignored. Or, worse, they demand a ton of information (company name, product name, manufacture of the product they are on, picture, etc.), then nothing, nada, no answers, or maybe some vague suggestion or something, but nothing of value to offset the massive amount of time they wasted. \$\endgroup\$
    – njs
    Apr 9, 2023 at 1:35
  • \$\begingroup\$ maybe one, or both, of the connectors is counterfeit \$\endgroup\$
    – jsotola
    Apr 9, 2023 at 4:22

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