DS1074Z issues with BNC - Page 1
Forum section: electronics / testgear

author: MatCat
author_rank: Frequent Contributor
timestamp: May 11, 2014, 08:13:43 pm
content: I bought mine from TEEquipment about 2 months ago and I am starting to notice on channel 1 to 3 that I have to rotate the probe BNC ever so slightly to get good contact, which really scares me that my new scope is already showing such issues, has anyone else noticed this?

author: 8086
author_rank: Super Contributor
timestamp: May 11, 2014, 08:27:23 pm
content: Just how much of a turn are you having to do? It's normal to turn a BNC connector to lock it in place, but If you are turning both parts (the connector on the probe wire and also the connector on the scope) there is a problem.

author: electronics man
author_rank: Frequent Contributor
timestamp: May 11, 2014, 09:02:51 pm
content: I have had mine since December, I have no problem with it the BNCs are very firmly mounted and don't feel like they are ever going to come undone.

author: MatCat
author_rank: Frequent Contributor
timestamp: May 11, 2014, 09:59:33 pm
content: It's an issue where you have to actually turn it so the inner connector rotates inside to get a good signal, the BNC mounted to the chassis is fine and strong, just seems like the inner connector is not connecting well, on channel 1 to 3.

author: linux-works
author_rank: Super Contributor
timestamp: May 11, 2014, 10:01:51 pm
content: maybe try pinching the inner connector on the scope (with needlenose pliers), to close up any gaps. some bnc might push 'wider' in the center pin than others.

author: Rory
author_rank: Frequent Contributor
timestamp: May 11, 2014, 11:40:31 pm
content: Still under warranty, isn't it?

author: tautech
author_rank: Super Contributor
timestamp: May 11, 2014, 11:48:16 pm
content: Two possible issues here, seen them both.1 BNC connections to PCB....solder cracked2 Probe BNC inner connector pin not making contact with socket female correctly. If you have always used the probes supplied there is no reason why the inner should be damaged.

author: MatCat
author_rank: Frequent Contributor
timestamp: May 12, 2014, 08:06:43 am
content: Quote from: tautech on May 11, 2014, 11:48:16 pmThe probes that come with it, the BNC patches that came with it (for the -S option), and a few other BNC cables.

author: tautech
author_rank: Super Contributor
timestamp: May 12, 2014, 09:18:15 am
content: QuoteExamine them carefully to ensure that their center pin has not deformed the socket female.Be suspicious ofanyBNC that takes any effort to socket or rotate the locking ring.IIRC Tek had a proprietary BNC that gave problems with other than their probes but don't quote me on this.Have a look at all your BNC's and it is likely you will find differing tapers on the center pins. Difficult to measure though without grinding down a set of verniers.

author: MatCat
author_rank: Frequent Contributor
timestamp: May 12, 2014, 09:44:49 am
content: Quote from: tautech on May 12, 2014, 09:18:15 amI might try to digital caliper them tomorrow and see if I can measure it, my roomate refuses to think it's the BNC patches because they come from a TV station...

author: tautech
author_rank: Super Contributor
timestamp: May 12, 2014, 10:37:35 am
content: Quote50 ohm/75 ohm I'm not sure that they might be a different standard?Had a look through my assortment of various probes & patch cables, there are many differing pin profiles, from small chamfer on the end of a parallel pin to a full length taper.

author: linux-works
author_rank: Super Contributor
timestamp: May 12, 2014, 10:54:34 am
content: there is a difference between 75 and 50 ohm bnc's. the 75 ones have a 'thin' outer shield on the connector that is not supported by nylon, like 50's are. but the inside pins should be the same.I would not blame the cables; I would probably blame the chinese connectors, to be honest. these are not going to be built like 30 yr old tek or hp.but again, pinching the inner connector with needlenose pliers will probably fix it up again.

author: tautech
author_rank: Super Contributor
timestamp: May 12, 2014, 11:57:16 am
content: QuoteBut they are not always. At least 4 different profiles in my collection.QuotePossibly.... wasn't Tek getting DSO's built in Asia 20 years ago?QuoteOn a 2 Month old scope?But we learn nothing from this.We need to get to the bottom of this problem for the good of all forum users

author: linux-works
author_rank: Super Contributor
timestamp: May 12, 2014, 12:32:31 pm
content: another thought: some used cables I bought were tarnished a bit and could use some kind of cleaning. if you transferred some dirt or grime to the center pin, now its going to need some cleaning (or replacement). I would not send a scope back and forth thru the mail just for that, though. I'd try to clean the center pin and make sure that any cables you plug in are clean.

author: tautech
author_rank: Super Contributor
timestamp: May 12, 2014, 12:35:34 pm
content: Quote from: linux-works on May 12, 2014, 12:32:31 pm

author: linux-works
author_rank: Super Contributor
timestamp: May 12, 2014, 12:38:02 pm
content: for tarnished metal contacts, I often use a rubber pencil eraser to remove the surface oxide. just alcohol isn't enough. but for an odd shape or hard to reach area like a bnc pin, it might have to be a more creative cleaning idea. maybe drill a hole in an eraser and push that around the center pin and twist it. maybe it would work

author: edavid
author_rank: Super Contributor
timestamp: May 12, 2014, 02:47:20 pm
content: Quote from: tautech on May 12, 2014, 09:18:15 amNot true.QuoteAlso not true, the pin diameter is (obviously) standardized.(And what's this about tarnish? Aren't BNC center pins gold plated?)

author: linux-works
author_rank: Super Contributor
timestamp: May 12, 2014, 03:28:47 pm
content: they should be gold, but some that I bought were pretty dirty. the cables used canare connectors (really nicely done, cant be done at home using DIY gear) and so I decided they were worth buying. but the centers are varying degrees of 'dirty'.if the OP has cables like mine, then this could be the cause.(my guess is that the environment was dirty and the gold connectors just got coated with junk. its not oxide, per se, but pollution, maybe?)