4 pin 7a or 2 pin 14a lemo B connector replacement? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: January 19, 2024, 06:30:41 am
content: I got a lemo connector (7A 4 pin) and I am disappointed by the 'quality'. The center plastic started to melt even after careful light soldering with a resistance tweezers leading to loose pins, and the cable strip diagram is hidden behind some kind of registration thing so I had to figure out how to strip the cable etc, plus the assembly of the cable is difficult (seems very tight to put the split shell into the body). And its from digikey.IMO lemo reputation is BS. I think the connector is bad. The fact that they try to make you register to access a assembly diagram is shady too, I think it means they are a marketing company not a engineering company.I wanted a screw lock circular connector preferably, but unfortunately the M12 connectors are only rated to 4.5 amps. Those are very good connectors in comparison. The plastic in those seemed more robust towards soldering. I kind of lost confidence in it since it so temperature sensitive. the stainless steel etc is useless if the plastic in the middle is trash. I bet it would fall right apart once the plastic in the middle loosened from the soldering despite all the engineering that went into some stupid pull lock mechanism/metal collet, which offers a false sense of security if a soldered pin or crimp is vibrating.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: January 19, 2024, 09:16:51 am
content: Hi coppercone2,what exactly did you order? There is no "7a" or "14a"-series, just 4A (triax) and 0A (koax).Post a picture and the complete part-number. If you mean Ampere, then write so.Maybe you picked the wrong isolation-material and the wrong collet for your cable...?The hotline here in munich is very helpfull and competent,they had an answer to my questions within 30 seconds. :-) Just phone them and be nice. ;-)But what the heck are "resistance tweezers"? And how do you solder Lemos with them??Good luck

author: Psi
author_rank: Super Contributor
timestamp: January 19, 2024, 09:31:56 am
content: Quote from: Roehrenonkel on January 19, 2024, 09:16:51 amResistance tweezers are a soldering iron system where you use a tweezer looking thing to solder by passing low volts high amps through the object you grab. The power heats up only the item you pickup and only between the points of contact.I've only ever seen really old and crude ones, but apparently (after googling) you can get modern ones too that look kinda cool.Not sure what type OP is using.Not to be confused with SMT or hot tweezers, which are just two normal soldering iron tips hinged together in a tweezer configuration for pulling off SMTs easier, since you can heat up both sides at once.Resistance tweezers are AFAIK not temp regulated, so OP may have heated the pin up to like 450C

author: Terry Bites
author_rank: Super Contributor
timestamp: January 19, 2024, 01:53:20 pm
content: Is it a genuine LEMO or a Chinmese knock-off?I've been using LEMOs for years and never had any quality issues or temperature induced failures.The insulator is PEEK and that can handle 170'C with no worries.I use a microtip iron, its fidly but you get used to it. I stick a socket in a minivice to hold it all steady while I solder.Solder the centre pin first then fit all the other conductors in the buckets and quickly solder them in. EasySo what if you need to register, it doesn't hurt (unless your a nutjob) and you can buy connectors from them direct. They cost less that way, cheaper than catalog suppliers like Mouser even in one offs.Tech help is firstclass

author: coppercone2
author_rank: Super Contributor
timestamp: January 19, 2024, 02:15:33 pm
content: are you really gonna call a tech support line for a god damn connector??I soldered a whole bunch of cheap ass m12 connectors and they were fine. A whole bunch of coaxial connectors and they were fine too. Something aint right with this. I already paid out the ass for this stupid ass connector and I am not gonna be on the fucking telephone to try to figure out a 100 year old solder cup technologyregister for a strip diagram too? after spending 70$. what god damn universe are these people from.how come RF connector companies sell stuff that is 5000% more engineered, 1000% more expensive, and just give you the damn cable strip diagram in the data sheet without the attempt to get a foot in the door. the practice is preposterous. Actually for the 70$ price tag, putting a piece of paper diagram in the package might be the least bit decent thing to do, it already comes in a ridiculous cubic meter sized shipping box that can handle being throw out of low earth orbit. You can remove 95% of the shipping material, save fucking 5000% on the paper, and still have it ship fine AFTER you include a strip diagram.if a god damn producer of little metal cylinders wants my email they better pay ME.

author: ConKbot
author_rank: Super Contributor
timestamp: January 19, 2024, 02:21:23 pm
content: I've done tiny (shell size 1 iirc) lemo connectors with a soldering iron and had no problem with melting of the dielectric. An you better believe I had way too much dwell time in the pin trying to get the tiny wire in there and flat.On a larger contact it shouldn't be a problem to follow good techniques to keep the soldering brief. Pre tin your wire with a minimal amount, pre tin your soldering cup with a minimal amount, wick excess if needed, lay the wire into the cup, add flux, then quickly hit the joint with an iron, add a small amount of solder so there is fillets, but it's not flooded, and you've got a sound joint. Take a break between each operation so the pin can cool, and it should be fine.I've heard of resistance tweezers used for dense soldering work in connectors, because they won't melt adjacent insulation from accidentally touching. but haven't used them. Sounds like the pin is overheating by a lot, given Lemo uses PEEK for the commonly available connectors.

author: coppercone2
author_rank: Super Contributor
timestamp: January 19, 2024, 02:35:38 pm
content: this paperless document registration email shit is like a obese man trying to get your phone number after he bragging that he leave the curl of decorative parmasan cheese of the 12 inch tall pile of lasanga he eating and calling it a diet.

author: tooki
author_rank: Super Contributor
timestamp: January 21, 2024, 12:17:22 pm
content: 1. Would you share the part number(s) of the connector in question?2. I don’t understand what all your rage is about. For the standard B series, as an example, the instructions are right on the website in the resources library, no login needed.3. The main catalog has all the strip lengths in the back, too…

author: coppercone2
author_rank: Super Contributor
timestamp: January 21, 2024, 08:25:59 pm
content: mainly that it god damn melted and the spin is spinning around and wiggling

author: tooki
author_rank: Super Contributor
timestamp: January 22, 2024, 08:12:15 am
content: For the third time: please share the part number.