BNC connection solder

[Enix316]

I noticed that my bnc connection was loose and also it seemed like the signal would go in and out. So I did a little disassembly and saw the the solder from the bnc to a post on the board was broken.

Got out my soldering equipment and got the old solder off.

I noticed there is a hole in the bnc connection post and I'm wondering if the board post should be put through the hole before I resolder it. I'm assuming it was done correctly at the factory and I should just put it back like I found it but thought I'd check what others thought first. Hopefully pictures clear up any bad explanation.

P. S. The brass nut was undone by me, it was much tighter originally, but still a little loose. Also, my pictures were too big so it was easier for me to send the pics to imgur

https://imgur.com/a/TXYmWln

 

[RFI-EMI-GUY]

If you make the connection to the post too solid, like a big solder blob, you risk tearing up the foil on the PCB. Use a piece of copper wire with a small bend in it so that any flexing gets transferred to the wire and allows some small amount of give. It wont make much difference if you put the wire though the eye of the post or wrap it. The wire diameter does not need to be very large and small will flex better. The nut on the BNC should be tightened firmly. It may not hurt to use some Loctite Blue 242 so that it does not wiggle loose. Avoid long stiff antennas that put stress or a lever moment on the BNC. If the BNC is worn, this would be the time to replace it. Assume that it may fail again, because these designs are notorious.

 

[Enix316]

If you make the connection to the post too solid, like a big solder blob, you risk tearing up the foil on the PCB.

This part makes sense, the original solder didn't fully encapsulate the post going to the pcb. It was kind of a taco blob, as opposed to a sphere.

Use a piece of copper wire with a small bend in it so that any flexing gets transferred to the wire and allows some small amount of give. It wont make much difference if you put the wire though the eye of the post or wrap it.

Just so I understand, you are suggesting using a copper wire wrap instead of soldering all together?

The nut on the BNC should be tightened firmly. It may not hurt to use some Loctite Blue 242 so that it does not wiggle loose.

I did plan on doing this, hopefully wont have to open it up again.

Avoid long stiff antennas that put stress or a lever moment on the BNC.

I would need to get another antenna then, this one is an old RS telescoping antenna that when fully collapsed is still quite long. That probably did contribute to the problem.

 

[RFI-EMI-GUY]

Solder should never be a blob, it should wet onto the mating conductor cleanly like a ramp. No I don't mean an unsoldered wire wrap. You can wrap rather than use the eye, either way is fine. But must be soldered. My intent was to have a small rounded bend in the wire so that if the BNC moves, the wire flexes rather than putting pressure on the post or PCB. You want a bit of a spring action.

 

[Enix316]

I'm not sure how I'd do that here. The bnc connection and post going to the pcb has no gap, now that the nut is tight.

 

[RFI-EMI-GUY]

I would carefully bend them apart or use some teflon tubing on the post or BNC pin to allow mechanical slippage and bridge with a wire. The way it is designed, the solder will crack again.

 

[RFI-EMI-GUY]

what radio is that?

 

[Enix316]

I would carefully bend them apart or use some teflon tubing on the post or BNC pin to allow mechanical slippage and bridge with a wire. The way it is designed, the solder will crack again.

So isolate and jumper, basically.

What about skipping the isolation part and just jumper it? So if/when flex happens the jumper is there as a backup?

 

[Enix316]

what radio is that?

A RadioShack pro-94

 

[RFI-EMI-GUY]

So isolate and jumper, basically.

What about skipping the isolation part and just jumper it? So if/when flex happens the jumper is there as a backup?

You could just solder the two parts directly together and not isolate it, but if it gets dropped on its head, the shock will go to the PCB and could cause surface mount parts nearby to pop off. It is a typical, but terrible design.

 

[Enix316]

Your logic makes sense to me. I'm not sure I have the skills to solder the little jumper but I will try.

 

[Enix316]

An attempt was made...