BNC socket fatigue

[targit]

Hi, My Micsig tbook mini gets a lot of use in automotive workshop environments and is starting to have trouble with the BNC female contact being stretched out and making intermittent contact with the probes plugged into it. I stripped it down with the idea I could swap the BNC socket from the trigger output which I never use with channel one input BNC but the amount of heat required to de-solder the body of the BNC from the PCB seems like I will de-laminate the PCB or otherwise melt the insulator in the socket.
 I have a possible idea for "repair", if I can find a BNC with a slightly oversize pin to make an adapter for the socket.
Does anyone know a brand/model of BNC which has oversized pins?

[chekhov]

Maybe you can mechanically cut old BNC out of the board, part-by-part, if construction allows that ? Or use 'dremel' ...
(of course in this case you have to buy new part anyway)

OR, if your workshop has such facilities, you can fabricate something out of piece brass with enough temal mass so that it has required holes that match pins on original BNC underneath. Heat it up, fill holes with solder and use it instead of iron to perform quick desoldering job. Maybe seems like one of crazy methods, but why not.
And heating original socket up to let's say 80-100C before doing that will also help a lot.

[Wallace Gasiewicz]

Can you put another BNC Female somewhere else on the case?If you can then just put a wire or a short coax from the board to the new connector and leave the old one alone.

[Georgy.Moshkin]

I desoldered tenths of BNC connectors from PCBs by keeping outer part of the connector (edge) slightly pushed against surface of heating platform set to 290 to 300 degrees Celsius. Then soldered to other PCBs. Temperature may depend on solder used. Although contact area was very small (thin circular edge), it heated up within minute or two and went out very smoothly, sometimes I needed to pull BNC connector with tweezers to heating platform direction,  and PCB to opposite direction. Plastic material inside connectors not melted, but I often do small repairs and resoldering, so can't guarantee on this. I think connectors probably must withstand 260 deg short term, not sure. I have used this heating platform, but a smaller size (image in attachment). I am sure that with heating gun I would damage PCB, because too much hot air moves around compared to heating platform.
Moreover, I've bought new BNC connectors for repairs few times, and struggled of soldering them for a long time (flux, grinding, 300+ Celsius soldering iron). All problems was gone after using heating platform: I set it to around 200 deg, put all BNCs upsidedown, preheated, and accurately placed PCBs on top of them, so BNC four ground pins and one signal pins inserted in PCB dedicated holes, and used 290 deg soldering iron to solder them one by one while keeping BNC edge pushed against preheating platform. But there was another problem, some LEDs weakly lit up when soldered signal pin of BNC, so there was some ac or dc present between platform and soldering iron, which is not good, and must be careful. Everything worked after repair though.

[tooki]

Preheating is absolutely the way to go.

[tooki]

OR, if your workshop has such facilities, you can fabricate something out of piece brass with enough temal mass so that it has required holes that match pins on original BNC underneath. Heat it up, fill holes with solder and use it instead of iron to perform quick desoldering job. Maybe seems like one of crazy methods, but why not.

That’s not crazy at all. I actually have a set of desoldering tips like that for DIP ICs, given to me by my old work, which has a large set of them for small and large DIP ICs, headers (all the way up to 96 pin, three row DIN 41612 headers), LCCs, etc. Tremendously useful, and the best way to desolder a large connector and have a chance it’s reusable afterward.

I don’t know why they’re not more popular, they work really well.

Maybe I will make one for BNCs myself, it’s a great idea. And for SMAs. I just had to desolder one at work the other day. (I did it with a preheater below, and a large chisel.)

[tooki]

Hi, My Micsig tbook mini gets a lot of use in automotive workshop environments and is starting to have trouble with the BNC female contact being stretched out and making intermittent contact with the probes plugged into it. I stripped it down with the idea I could swap the BNC socket from the trigger output which I never use with channel one input BNC but the amount of heat required to de-solder the body of the BNC from the PCB seems like I will de-laminate the PCB or otherwise melt the insulator in the socket.

I found some video of the board, and it looks like it’s designed to take multiple common BNC footprints, so replacing it shouldn’t be that hard.

With that said: are you sure it’s the BNC jack? I’d think it more likely that the probe or cable is failing.

I have a possible idea for "repair", if I can find a BNC with a slightly oversize pin to make an adapter for the socket.
Does anyone know a brand/model of BNC which has oversized pins?

I should certainly hope not! BNC is a standard, and making a plug with oversize pins that will mate with a standard jack, causing damage to it, would be lunacy. (Plus it would change the electrical characteristics, which are a controlled value).

If you absolutely had to do such a thing, I’d buy a “port saver” (that is, a simple male-female “adapter”) and add a tiny bit of solder to its pin to thicken it up. But if you do, clearly mark it as such so that nobody inserts it into another jack, damaging it.

I’d just replace the jack.

[floobydust]

OP be careful it's not the male pin on the probe etc. that is trashing the BNC female.
I once had a bent/mangled male pin that people were forcing in and that was wrecking the BNC's in the lab.

[targit]

Thanks for all the ideas, as this is inside the front end can I am mostly worried about over heating the PCB and having tiny SMD components drop off which is why I thought of the oversized pin.
I have tried other probes and the fault is reproducible with any other probe, and the probes are fine with other scopes, so I am pretty certain its the socket at fault, it takes quite a bit of wiggling to get the fault to occur on the bench, but when I am in the field it will happen every couple of minutes with no effort at all. The pictures hopefully show the socket(s) to be the issue compared to the Aux Out that I have never used.
Only after I just put it back together have I remembered the Chipquick low melting point solder that I bought for desoldering tricky multipin packages. I have never tried it on anything with this kind of thermal mass, but I reckon a combo of making up a brass tip and using the Chipquick might be the go.
Doesnt look like I will get too many goes at taking the screen bezel on and off so I will try and find a scrap pcb to practice on.
I had thought of wetting the probe pin or an adapter pin with silver solder as suggested, and that is maybe the way to go if the Chipquick doesnt do the trick.
Thanks 

[targit]

Hi, I just realized I forgot to match up the sockets for a replacement part , I have been searching through parts websites but not finding any that look quite right, can anyone name that BNC connector as per Mikeselectricsuff teardown video

https://youtu.be/DNou_H-kHZY?t=1031

Thanks

[Hamelec]

https://www.google.com/search?q=bnc+pcb+socket&tbm=isch&ved=2ahUKEwiIxNrXypf_AhXxvUwKHQOAAEkQ2-cCegQIABAA&oq=bnc+pcb+socket&gs_lcp=CgNpbWcQAzoHCAAQExCABDoICAAQBxAeEBNQxglYjRBg_BFoAHAAeACAAT-IAYgCkgEBNZgBAKABAaoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=Nw9zZMjMNvH7sgKDgILIBA&bih=1002&biw=1904&client=firefox-b-d#imgrc=_SHPum1X57y5cM

https://www.fairviewmicrowave.com/bnc-female-connector-fmcn1814-p.aspx

https://www.klselectronic.com/kls1-bnc067-pcb-mount-bnc-connector

.. you have to check dimensions

[chekhov]

Seeing this image, haven't you tried to unscrew the 'tab' (no idea how to name it) at the back of the connector ? That really opens the possibility of replacing just central connector from the other one ...

[tooki]

Thanks for all the ideas, as this is inside the front end can I am mostly worried about over heating the PCB and having tiny SMD components drop off

Trust me, that's not going to be a problem unless you try doing this with hot air, which I do not recommend at all.

Preheat the board (= still below melting point, which is 217C), then your iron only has to add a far smaller amount of heat. For example, preheat to 100-150C.

If you have a machine shop, I really would consider chekhov's suggestion of fabricating a high-mass desoldering tip which can heat all 5 pins at once. I would avoid the ChipQuik low-temp solder if you can, because it will make subsequent solder joints brittle, which is the last thing you want on a BNC connector, unless you can truly remove all traces of the low-temp solder by "rinsing" with regular solder several times. With preheating and a high-mass desoldering tip, this should be no problem.

[tooki]

Hi, I just realized I forgot to match up the sockets for a replacement part , I have been searching through parts websites but not finding any that look quite right, can anyone name that BNC connector as per Mikeselectricsuff teardown video

https://youtu.be/DNou_H-kHZY?t=1031

Thanks

The picture alone is not enough, since you need to know the overall length of the connector, but almost more importantly, the height, since there are several common heights. With the wrong one, it won't fit through the hole in the case.

[coromonadalix]

want a cheap solution add an female to male adapter, it will be to one who'll take the wear and tear,  change it a 500 connections, you will save the ones on the instruments

i do that on my sectrums and signal generators   .... and one scope, who do not need the probes

[targit]

I found that I could "repair" the BNC socket by using a very thin pick to push the contacts in the socket together enough to make a good contact, and then using flying leads as suggested to take the strain off the plugs, so now have it working for the time being until I can get some sockets for a proper repair.

 

[HighVoltage]

... and then using flying leads as suggested to take the strain...

Where did you get these "flying leads"?

[targit]

I made them.

[HighVoltage]

Very nice!

[tooki]

I found that I could "repair" the BNC socket by using a very thin pick to push the contacts in the socket together enough to make a good contact, and then using flying leads as suggested to take the strain off the plugs, so now have it working for the time being until I can get some sockets for a proper repair.

 

While I like this solution in theory, beware that unless your signals are quite low frequency, you shouldn’t extend oscilloscope cables because the cable itself is part of the probe (it’s not normal coaxial cable). See https://www.eevblog.com/forum/beginners/extending-scope-probe-leads/

If in doubt, use simple BNC port savers (short male-female adapters) instead.

[targit]

The scope is exclusively for automotive use, so the frequency is way under  1MHz  and often not more than 30KHz . I wanted to avoid plugging/unplugging the "repaired" terminals as much as possible and also
avoid moving the socket around too much, I found that 90 degree adapters put too much mechanical load on the connection and the fault re-occurred after a few cycles.
I got the crimp on line sockets from Jaycar and the solder on right angle plugs from Altronics (I bought their solder on line sockets first but they were garbage).

I did try the "wetting the pin with solder" method but that was no good.

Thanks for all the suggestions and help

[targit]

So Everything has been working fine with the flying leads  -- until today when I had to use my clamp current probe and the BNC plug was very difficult to insert into the inline socket, I had to really push to make it go in, and then after looking at the socket it now has "stretched out" same as the scope sockets. I measured the pin on the clamp using Starret electronic calipers, it is 1.35mm versus the 1.3mm of other plugs I checked. The spec. says 1.32 to 1.37 . If I set the calipers to 1.37 gap and put the 1.3 pins in, they are a very loose fit. I know the socket contacts should have some "spring" in them but it seems they cant cope with the fatter end of the spec range without becoming "stretched out".

The fatter pins were on the plugs in the PDF

The thinner ones are no name plugs I think came from Jaycar.

[tooki]

Honestly, I can’t help but wonder if there’s some degree of user error here. BNC connectors have been around for around 80 years, and if there were mateability problems between manufacturers, this would be a known problem by now (the way it is, for example, known that there are compatibility problems between certain types of banana plugs and sockets). Meanwhile, you’ve managed to have the same failure mode with two unrelated sockets.

The BNC whose datasheet you show is a Stäubli, which is extremely high quality. There’s zero chance they aren’t completely compliant with the standards. You measured it at 1.35mm, which is precisely what it should be: right in the middle of the tolerance band.

So either all of the BNC connectors on your scope AND the BNC connectors on your leads were all made out of spec too small, or something else is happening. It seems within the realm of the plausible, to me, that jamming in a connector off-axis (rather than backing off and trying to realign better) could damage a contact.

The other thing that comes to mind is this: what if one of your plugs has a perfectly sized, perfectly round, but bent (or otherwise eccentric) center pin? That would measure as the correct diameter, but could distend a female contact on insertion.

(That is reminiscent of the DVI connector’s susceptibility to a “hardware virus”, wherein a bent pin in a plug will damage the socket — and damage it in exactly the way that causes the socket to bend pins on other plugs in the exact same way as the original damaged plug!)

[targit]

Hi, I have been using BNC plugs for 30+ years, so I am pretty sure I know how to insert a plug - I don't just try and jam a connector in off axis. The Staubli pin I measured is brand new unused and yes I agree it is right within the spec range.
My issue seems to be the sockets which do not accommodate the full spec range of pin sizes without losing the contacts "spring" .
None of my other scopes suffer this problem, maybe as the probes are rarely unplugged, this scope gets disconnected and put back in its box every time its been used, so I would expect some degree of wear on the contacts after several years of use, but the flying leads were made with no-name sockets from Jaycar so they might not be of the highest quality.

[targit]

I have since tried connecting the pinless un used body of a Staubli BNC plug to the Jaycar BNC line socket and it will not mate without applying more force than is reasonable.
 I took a closer look with some magnification and it seems the Jaycar line socket dielectric is too large in diameter (it mates ok with a Jaycar BNC plug).
I found the Altronics line connector mated OK with the Staubli plug - but I could not use it due to the very poor mechanical cabe screen connection/retention of the Altronics part.
The plugs of my Micsig DP10013 mate OK with the Jaycar line sockets.

The Jaycar line socket is CAT.NO:  PS0660

I attached the PDF which includes a dimension spec for the BNC in metric and imperial. For some reason I struggled to get a google result that wasn't in inches and maybe its useful to someone else.

I will order some high quality connectors to make up some better flying leads now the concept has proven to solve the issue I was having.
 I think this solution beats replacing the scope sockets as it removes all mechanical strain on the instruments connectors.