reseating MTA connector wires? (IDC) - Page 1
Forum section: electronics / repair

author: coppercone2
author_rank: Super Contributor
timestamp: January 13, 2023, 09:19:27 pm
content: So if you have a MTA connector (IDC type), that has a wire come out of it, can you reseat the wire by lodging it in there with a screw driver, or should you really just replace the whole connector?Like, I was under the impression that it involves cold welding. If the wire pops out, that means the cold weld broke. Are the surfaces suitable for reseating? Can you even get a good fit without using the crimp tool. I used the real crimp tools before but it just feels kinda weak, but I am wondering if it depends on precise geometry of the connector. It does appear to work when I pressed a wire back in there, but I wonder how bad it is.https://www.tindie.com/products/clockworks/mta-100-8-and-12-pin-cable-assembly/

author: berke
author_rank: Frequent Contributor
timestamp: January 13, 2023, 10:50:39 pm
content: When you push a fresh bit of wire into the slotted MTA wire receptacle, the slot displaces the insulation from two sides and then eats into the wire from those sides. Maybe that's where the "cold welding" action happens, and why you need to pay particular attention to the wire gauge (in your case that shouldn't be a problem.) The thing is that the tool (I have the little dinky 35 buck hand tool) has teeth that allow you to push the wire by two ends over the U-shaped slot/receptacle, but without pushing the slot itself. I'm not sure how you can achieve that effect with an unodified screwdriver. Even with the tool MTA connections are a bit so-so IMHO.If you have the hand tool, pull out the offending wire, trim it so you get a fresh start and then you should be able to push it back in with the tool, I've done so a couple of times and it seems OK.If you don't you might make a decent MTA tool by taking an old screwdriver and filing a little slot in it.I wouldn't personally trust wire that has been just pushed in with a screwdriver.

author: coppercone2
author_rank: Super Contributor
timestamp: January 13, 2023, 11:47:58 pm
content: I think its designed so that the wire makes a cold weld with the knife fork, but the thing is, that only makes sense for solid wire. I don't know whats going on with stranded IDC wire. I guess it would only cold weld to a few of the strands,but some how this is considered reliable in industry. I am guessing its too dull/deformed to do the same kind of action again after 1 use.I don't think there is enough pressure there to cold weld the entire bundle together.I have a power supply where I reseated a wire, and it works OK, but I am thinking that I should replace the whole harness before it does something stupid like output maximum voltage randomly and destroys something more expensive then the cable.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 14, 2023, 02:51:10 am
content: to use a screw driver you need one with almost the same size as the cable slot in the pin, slightly narrower, to be sure it will not expand the pin cable "slot"i used a buffer to adjust itand you need a straight constant width, and you gently push all the way ... never had problems ??

author: coppercone2
author_rank: Super Contributor
timestamp: January 14, 2023, 02:54:34 am
content: but like, are they supposed to be cold welded or are they press fit? Like does anyone have background on that connector that explains the physics more then a machinist 1 page diagram?

author: coppercone2
author_rank: Super Contributor
timestamp: January 14, 2023, 03:01:15 am
content: https://www.kyocera-avx.com/news/the-history-of-insulation-displacement-technology/Like this one shows cold welding, but thats not a MTA connector, and it also does not really explain stranded wire. I guess they show stranded wire in the diagram but I don't get exactly whats going on in there... and if the blades can be reused its a big mystery, I know the defacto way to fix a ribbon cable is to press it down in a vise.I guess it can be called iffy?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: January 14, 2023, 03:35:54 am
content: For the intended use case MTA connectors are IDC, not cold-weld like a proper crimp. They only work for stranded wire with basic insulation like PVC. For instance, they won't work with Teflon. Ideally use the proper tool.For non-production use, the screwdriver method works, but be careful about forcing the blades of the terminal apart. This will just make it easier for the wire to come out. Solid wire can be made to work, if it's oversized and held in by the teeth meant to hold in the normal wire. Otherwise in a pinch solder the wire in place.

author: coppercone2
author_rank: Super Contributor
timestamp: January 14, 2023, 03:44:28 am
content: the avx website says that they are cold weld. And I don't know about crimps being cold weld, I find the IDC thing being more plausible, I took apart crimps that were done properly and after grinding wires were comming out easy with a pick. The only thing I trust is a cold weld is a wire wrap post. I give IDC a "maybe" because the bond area is really small and focused.The wire wrap thing makes sense because there is a enormous amount of force on a sharp corner of a square post. IDC I think "kinda" because the fork is really small and its a wedge. Circular crimps I think might be gas tight but I don't think it is cold welded.