Beware - Certain types of HIRSCHMANN plugs get stuck, won't come out of 34461A - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: November 03, 2017, 10:03:17 am
content: Hi guys,So, I bought some banana plugs, namely the type BUELA 20 K, made by HIRSCHMANN, made cables from them, plugged them in my Keysight 34461A, done my measurements... and one of the bastards won't come out.I'd guess that the head is stuck, since the construction is such, that 6 plated bits are springy and when inserted make contact with the outer tube of the socket. The tip of the plug is a metal bit that holds them in place. This means that the diameter of the body of the plug can be smaller than the tip, when the springy bits are pressed into the body.I'm guessing that the sockets in the Keysight device are a tube, but not all the way through - as such the head got caught on the end of the tube and the bastard won't come out. Bonus points if the head gets deformed by more frustrated attempts at pulling it out, making it more stuck.So, yeah. This will be fun.Attached are the photos of the culprit.

author: daqq
author_rank: Super Contributor
timestamp: November 03, 2017, 10:12:40 am
content: Update: After using much more force than I'm comfortable with when used in combination with a pretty damn expensive meter I pulled the plug out... without the tip, which is probably still stuck in the socket. Also, a quick inspection of the socket reveals some internal damage - a small bump in the metal. I can't make a photo of it at the moment.

author: cat87
author_rank: Regular Contributor
timestamp: November 03, 2017, 02:23:53 pm
content: Where I work, we have many types of banana plugs, among which the same Hirschmann as you have. And I've noticed the same issue with these. It's that damn dome in the end of the banana jack, that gets stuck and is a real pain to pull out. I've even had the thing get stuck in another banana jack.Now, I stay away from any plug that has the same type of tip on it. I prefer the jacks from Schutzinger. They seem to be much more robust and tend to have a nice contact pattern with the mating jack

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 03, 2017, 02:32:32 pm
content: Quote from: cat87 on November 03, 2017, 02:23:53 pmIs the type pictured the right or the wrong type?

author: capt bullshot
author_rank: Super Contributor
timestamp: November 03, 2017, 08:01:58 pm
content: I don't use this kind of plug anymore for many years.

author: Vtile
author_rank: Super Contributor
timestamp: November 03, 2017, 08:34:10 pm
content: Quote from: cat87 on November 03, 2017, 02:23:53 pmbeware of the cheap connectors of these type (type 5. in picture), almost everyone of them have substandard connection when wires/leads are moved. It also seems that some of the "Chinese" factories are littering (based on my two online orders) the markets with too tight banana sockets.In my mind variations of this mechanical contact structure of the type 1 and 2 are really good ones and actually the connector 2 in picture is a standard test leads for Unigor 6e meter. The best ones are the three finger connectors numbered 4. and close to that are the type 3 (Pomona seems to like it)., but it usually is "too short".

author: HighVoltage
author_rank: Super Contributor
timestamp: November 03, 2017, 09:57:05 pm
content: I had this problem once, many years ago and damaged a 34401A.Since that time I have never again plugged a Hirschmann banana plug in to an expensive instrument.I am using only gold plated MultiContact (MC) banana plugs since then.The first time you insert one of these, you feel the quality!

author: Vtile
author_rank: Super Contributor
timestamp: November 03, 2017, 10:10:48 pm
content: ^^ That almost sounds like one of those audiophoolery reviews.Edit. This "The first time you insert one of these, you feel the quality!" part.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 04, 2017, 08:37:26 am
content: Quote from: Vtile on November 03, 2017, 10:10:48 pmFunny: It does sound like it.Also, watch out for some of those banana plugs that have a plastic (dome) tip at the front.Some of these plastic tips are so tight, that they start expanding from the temperature of the instrumentand then they are so tight inside the receptor, that you can not take them out anymore.

author: cat87
author_rank: Regular Contributor
timestamp: November 05, 2017, 12:44:06 pm
content: QuoteThe picture is the kind on banana plug I DO use. Notice the Hirschmann has the bit on the tip riveted, while the Schutzinger one in my previous photo has a different way of holding the tip (brazed perhaps? or just turned?)On the Hirschmann, the rivet tends to loosen and the tips is no longer is line with the rest of the lead, that's why it gets stuck.I've also used No.1 and No.2 plugs from Vtile's photo and are also quite good, except the contact pattern may not be well suited for some high-ish current applications (> 3A). At least that's whay my mind thinks.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 05, 2017, 01:25:46 pm
content: I had a similar problem with one of the Hirschmann or similar plugs too - though not in an expensive instrument, but a self made box and rather cheap terminal (just a tube open at the end). So in this case I could see the inside and remove it reasonable easy.In my case to cap at the front of the plug was bend a little, maybe stepped on it, dropped something heavy on it or maybe just bend to the side when removing from a terminal.Otherwise this type of plug is rather good. It is more like the simple split plugs like No 4 type that can have poor contact.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 05, 2017, 01:57:04 pm
content: I experienced the same problem on a Beckman DM25xL. I traced the condition to a less than perfect fit of the thin hemispherical cap in combination with PCB-mounted jacks, which have a distance from the PCB (except for the solder pins), which allows the rim of the cap to get caught.

author: daqq
author_rank: Super Contributor
timestamp: November 12, 2017, 12:56:02 pm
content: OK, after some testing, the plugs are usable (safe), if you remove the metal cap. That said, I'm never touching this particular type again.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 12, 2017, 01:11:07 pm
content: Hirschmann SKSmakesa lotof banana plugs.This type with the spring wires put into rings it a high insertion force type, probably for high current, and you can't stack them touch safe. I don't know why people even get these.The one with the bent sheet metal as shown bycat87is much better.There is also the one with a single curved strip, it will be loose quickly.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: November 13, 2017, 04:02:58 am
content: It seems right - BUELA 30 K (20K ? ) -30 Ams rated, MZS 4 - probable better in this application