Staubli (MC) 4mm CuBe plugs and imitations. - Page 1
Forum section: electronics / general

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 30, 2025, 04:24:54 pm
content: Separated fromanother thread, not to get OT there.I prefer these Staubli (MC) to any other 4mm plugs as they are long lasting, stackable, easy to assemble and disassemble, make a good contact , have a very low mass and the beryllium copper is good from the thermal EMF side. I use these for all my metrology stuff, with voltage and resistors references and these are consistently give an excellent performance, keeping DC offsets very low and contact resistances stable. Lately my usual sources (Farnell UK and RS) stopped stocking these and I assumed that production has stopped. There areimitations of the metal insert you can get from eBaybut these Chinese variants are difficult to use due to an imprecise shape and burrs which I had to file off (together with the gold plating, obviously).In the original thread a couple of members gave pointers to where the genuine Staubli plugs are still available, with proper isolation bits in various colours. I immediatelybought a quantity from Poland (TME)and on arrival was somewhat disappointed that the plugs were different from the original matt plated ones, with a shiny gold plating similar to the eBay version (though much better made and without burrs). Just to make sure that now Staubli changed the bit, I'veorder another quantity from Burklin in Germany. Now I have all four sourced plugs on my bench and, as promised, looked for the differencies.In short, plugs from TME and Burklin are identical, well made with clean de-burred edges and have a conical shape with the diameter at the back (~4.6mm) larger than at the front (~4.25mm). The original "old stock" plug has an oval shape at the front with 4.0 x 4.4 mm size and round 4.6mm at the back. The Chinese eBay version is cylindrical, 4.2mm an the front and back, much more difficult to stack, with burrs and sharp edges which are trying to cut into a socket sides when in use.UPDATE 04 July 2025 - new version metal bits from Staubli as supplied from TME and Burklin are MAGNETIC which might indicate a Ni layer under gold plating or a different Cu alloy. The old version (matt gold plating) is NOT MAGNETIC and the eBay Chinese plugs are NON MAGNETIC.Conclusion -the current plugs are almost as good as the original ones and I am happy these are still available from proper sources and at a very good price.Nothing is perfect.CheersAlex

author: tggzzz
author_rank: Super Contributor
timestamp: June 30, 2025, 10:38:34 pm
content: That's a remarkable example of synchronicity; I was just about to start a thread on this topic!It does indeed appear that Staubli has stopped making them, so thank you for finding alternatives.

author: gmac34
author_rank: Regular Contributor
timestamp: July 04, 2025, 08:08:40 am
content: Did you notice any difference in the EMF "behaviour"?The difference surface finish may mean that the plating process has changed, the new one probably have a nickel substrate under the gold, I wander if the old were a more expensive thick gold plating on bare copper

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 04, 2025, 12:22:44 pm
content: Well spotted, that is one side I didn't check (getting older I suppose). The results are interesting - I've used a small strong magnet to check.The old "original" matt plugs are NON-MAGNETICThe new version plugs from both TME and Burklin are MAGNETIC, which indicates a Ni layer or a different composition of the Cu alloy. I've tried to check by scratching the gold layer and I couldn't see a Ni layer even with a good metallurgical microscope at x400 magnification, only copper and gold. Normally I would expect it to be visible.The eBay version, while mechanically inferior, is NON-MAGNETIC!Nothing is perfect it seems. I might do some Thermal EMF checks just to see if there is a measurable difference... .CheersAlex

author: tggzzz
author_rank: Super Contributor
timestamp: July 04, 2025, 12:53:57 pm
content: I've just received a few from TME, and can confirm they are magnetic - unlike those I bought a few years agoCan I suggest you edit/update your first post.Such mistakes are easy to make. I've bought some Staubli leads, only to find they are 2mm, not 4mm. Doh!

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 04, 2025, 01:02:27 pm
content: Quote from: tggzzz on July 04, 2025, 12:53:57 pmDone, thank you!CheersAlex

author: tggzzz
author_rank: Super Contributor
timestamp: July 04, 2025, 01:16:31 pm
content: Maybe we could flip the magnetic ones on fleabay for £10 each..."Magnetic gold 4mm plug inserts, ideal for audiophoolfile applications. Unlike the original non-magnetic plugs, these have been improved by adding a small magnetic layer between the gold surface and copper body"

author: gmac34
author_rank: Regular Contributor
timestamp: July 04, 2025, 01:30:52 pm
content: I did not check if mine where magnetic, but they problem are, as they where recently purchased from Burklin.For the Ebay ones, did you find some actually made of copper? al the ones that I have bought were brass, either copper or gold plated, and definitely had worse thermal emf performance that the Staubli ones.

author: PrecisionFreak
author_rank: Contributor
timestamp: July 05, 2025, 10:44:24 pm
content: we are talking about MC multi-contact LS4 22.1005Laboratory plugs, 4.0 mm, type MC LS4. Eur 1.88 @1 at Bürklin (now in stock = 231)It's time to check for sellers with old stock, also the sets with isoltion 22.2060.xx or try to get cables fitted with them (LK4-B, LK4-B Sil, LK4-B1,5)https://www.farnell.com/datasheets/9604.pdfother sources:https://twen.rs-online.com/web/p/banana-connectors/0531453

author: coppercone2
author_rank: Super Contributor
timestamp: July 05, 2025, 11:04:50 pm
content: wow that plating looks like proper shitI think they did a fast plate over grease or something. My DIY stuff looks 100x better

author: gmac34
author_rank: Regular Contributor
timestamp: July 06, 2025, 05:27:33 am
content: If you refer to my pictures, those are examples where I removed the plating to see if there was copper underneath. Both are AliExpress grade claiming to be copper but actually made of brass. I haven’t tortured the staubli ones yet

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2025, 07:58:30 am
content: oh ok I got scared that someone sold that lol

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 06, 2025, 09:33:16 am
content: I wonder, which barrier layer multi contact has used in former days, than a nickel one.My 30 y/o plugs with PVC cables from mc are non magnetic as well, but the hard plated gold layer is still fully intact, even after 30 years of heavy use..The question about e.m.f. for the new Ni barrier layers is irrelevant, to my opinion.In my old assemblies, the plugs are directly crimped to the copper strands of the cable, so this contact e.m.f. is neglectable.Nowadays, you need to solder your "new" plugs to your cables, therefore this solder joint is the only relevant e.m.f. source, so you can completely forget about the Ni barrier layer.I have soldered 2W PTFE cables with the old mc plugs for precision absolute DCV measurements (of my LTZ1000 references), and I found that the emf of my DIY cables is always well below 300nV in practice , i.e. < 0.03ppm error. I also assign this mostly constant offset to an expired CAL 0 calibration of my 3458A.Btw.: I still have enough stock of these old mc plugs, as well I got a lot of complete, old cable assembliesAnyhow, I'm meanwhile using DIY PTFE cables with crimped copper lugs only, and the current problem is to find gold hard plated ones, which would withstand the usual use.I got lugs from China, where the gold plating is vanishing after a few years, obviously made w/o Ni barrier layer, either because the gold layer is too thin, or beacuse they didn't use the hard plating process.Any hints to such better lugs is welcome.Frank

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2025, 09:39:28 am
content: what if you just solder em with cadmium, very carefully with a fume extractor, and then possibly give it a coat of sealant if you are scared of it. It should be well contained in a little solder cup anyway,

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 06, 2025, 09:42:22 am
content: Quote from: coppercone2 on July 06, 2025, 09:39:28 amAs said, that would be of no practical use at all, because the emf is always very low even for leaded solder joints, and I cannot really assign the residual 300nV (possible 0.03ppm effect) to the solder joints.Frank

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2025, 09:43:49 am
content: Oh I thought you meant that it was the root of all your problems

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2025, 09:47:40 am
content: Hmm for coating , I was doing experiments for dip coating stuff. I managed dip coating/soldering in 56% silver braze in a small crucible for copper wire. That stuff melts easy and its reeallly easy to use/works well. The layer is thin and uniform. stuff is real fluid. I mean its a real film, not some blotchy crap with high spots etc.I got it to work on copper wire with pure silver once, but it was real fast, and I melted my test joint into the silver when I tried again. Pure silver melts kinda hot.But, for gold alloys less then 24K, you can melt em at a lower temp. IDK what is the minimum karat value you can use, but I suspect it might be possible to dip coat some stuff with gold. No chemicals just get gold to stick to it. A gold silver mix... I suspect it works much like paint. 14k should be childs play. 18k I am not sure, 20+K might need an aparatus to dunk it for you so it does not melt, depending on what it is. Or real tight temperature control. 14K i bet you can do with a blow torch easy. The lug should be easy because its massive. As hot as it is, not enough heat transfers through it to melt it instantly. SIlver is worse because the thermal conductivity is the best. Gold is like 25% less then that. You just can't dilly dally with it.I am going to go out on a limb, that using a 23k gold (with a little bit of silver to help it flow and adhere) should be very possible on a fat copper lug.But you need to be good not to over heat the stuff.But if you try,. make a silver alloy that melts at a similar temp and try it yourself, before you contaminate a crucible of gold with molten copper

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 06, 2025, 10:25:12 am
content: just to illustrate the deterioration of these Chinese lugs, I add a picture, together with the mc plug from old stock.Btw.: No, I don't have any problem with emf from plugs, lugs, cables, whatever.It's only of cosmetic relevance, and I'm currently doing research on reducing the uncertainty of DCV measurements for my LTZ references.This is limited due to noise of the references, of the DMMs used (3458A, 1271 as I have to make absolute measurements in contrast to differential ones) and due to time and temperature induced drifts.These effects are on the order of 200nV StD for DMM measurements and the references, and about 1µV Std for drift effects over the ~45min transfer time window.Therefore, any (varying) emf errors are completely irrelevant in proportion and I don't waste any thought about this topic, before I don't manage to greatly reduce these other effects.Frank

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 06, 2025, 06:38:53 pm
content: To be of real benefit for Alex, instead of posting such OT stuff, I'll instead publish my geometric measurements on proven 30y/o and genuine mc plugs:D2 = 4.51mm/4.2mm (perpendicular diameters)D1= 4.65mmH1 = 30.08mmH2 = 5.04mm