What Connector is this? (Three-Lug minature bayonet connector) - Page 1
Forum section: electronics / repair

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 08:54:43 pm
content: Does anyone know what connector this is? It looks like a miniature, three-lug bayonet connector.I don't actually own this Dymec part, but I have what I believe are the male connectors in a bin and can't figure out what these are called.

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 09:04:37 pm
content: It is a Triax 3 lug connectorhttps://uk.farnell.com/keithley/237-bnc-trx/conn-3lug-triax-bnc-w-guard-discon/dp/2460226

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 09:10:28 pm
content: No, this isn't triax. This is coaxial (only two conductors). It does have three bayonet lugs like modern triax though (older Keithley triax had two lugs and I have seen four-lug triax as well).

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 09:11:19 pm
content: The datasheet on the Farnell page begs to differ with youIt is a Triax type connector without the guard connected.https://www.farnell.com/datasheets/2574011.pdf?_gl=1] https://www.farnell.com/datasheets/2574011.pdf?_gl=1*1fg3sz5*_gcl_au*MjM2NTg2NDAzLjE3NDAwODUzODg.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 09:14:28 pm
content: Fraser... This is not triax. I own plenty of triax, this connector is smaller and has only two conductors. It looks similar to the small connector used on old Tektronix plugins. It does have three bayonet lugs like _modern_ triax, so I can see why you are confusing them.

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 09:16:35 pm
content: Please read the data sheets. I know Triax as well but there is a version of the three lug Triax connector that does not have the guard connected. Believe your own eyes by checking the data sheets that I have linked to.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 09:17:52 pm
content: Here's a photo of a male connector I have. You can see that this is a normal coaxial connector, but miniature and with three lugs.

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 09:20:21 pm
content: I attach the description page that shows the connector in detail.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 09:24:31 pm
content: Fraser, I don't know why you insist that this is triax. It is not. Thanks for replying anyways.

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 09:25:29 pm
content: So this connector is a miniature BNC size ? I used to have some of those miniature BNC format connectors but with 2 lugs. Thanks for the picture.Sorry I cannot help.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 20, 2025, 09:32:27 pm
content: Yes, it is closer in size to a miniature BNC or the small bayonet connector used on old Tektronix plugins (BSM). This particular male connector uses RG-174 cable.

author: Fraser
author_rank: Super Contributor
timestamp: February 20, 2025, 10:13:32 pm
content: Sorry for heading off down the wrong track. With no dimensions for reference it looked very much like the guardless Triax connectors I had used in the past but I now see that the size is totally wrong. I will see if I can find the manufacturer of my miniature BNC connectors as they look just like yours, but with only 2 lugs.

author: squadchannel
author_rank: Frequent Contributor
timestamp: February 20, 2025, 11:46:49 pm
content: TPS connector?https://www.digikey.com/en/products/detail/cinch-connectivity-solutions-trompeter/BJ50/2747509

author: coppercone2
author_rank: Super Contributor
timestamp: February 20, 2025, 11:50:35 pm
content: that might be a pain in the ass connectorI wonder why. Does it have more vibration resistance?It says they reduce rocking. I don't feel any rocking with any BNC connectors though. Unless you like yank on it but I figure at that point the shield is getting hurtI did take measurements before though, with high Z things, if you bang on the connector (i.e. splice interconnect) you can pick up some noise. So infact I do think its meant for electrometer like things. Contact motion does make a measurable signal spike. I had a long cable with a connector pair in the middle. Held that firmly against the bench and wiggled, lifted, smacked, etc the cable, and there was nothing being measured. If I did the same thing with the splice area, you could read it out on the graph. This points me in the direction that its the connector and not the cable (people do blame triboelectric cable effects for everything, but the connector might be more involved then you think for some systems).

author: Fraser
author_rank: Super Contributor
timestamp: February 21, 2025, 12:02:50 am
content: Three lug connectors were often used to prevent accidental insertion of an otherwise very similar 2 lug connector, or vice versa. With the Triax connectors it was done to prevent users pushing a BNC plug into a Triax socket.

author: TimFox
author_rank: Super Contributor
timestamp: February 21, 2025, 12:11:51 am
content: Similarly, MHV connectors (two-lug) were common victims of unnatural mating with BNC connectors, which was not pleasant for either sex, and BNC connectors could not hold as much voltage as MHV (typically used for 1 kV to 3 kV into a PMT or similar high-voltage device).At university, we replaced all MHV connectors with SHV connectors that are non-mateable with BNC or MHV connectors.