I have the older original style Uputronics 1090Mhz SAW preamp. I was reworking the setup and screwing in some LMR400 and the SMA connector started spinning, and then came out. Has anyone had that happen? I can’t see any obvious way to reattach it other than push it in, but it’s a tight fit and seems to have nothing to make it stay.
The pin you can see sticking out is actually a tiny tube, it’s the part that receives the actual solid pin in the connecting coax or adapter. It’s supposed to poke all the way through the brass part and be flush with the end of it.
I emailed Anthony at Uputronics in case he has any suggestions for the right way to fix it, if it is fixable.
I suspect the very rigid LMR400 and flexing has either caused it to work loose or else it has actually sheared off, but I suspect the former.
I had the same issue once.
Fixed it by opening up the case and taking the PCB out.
Set up the connector, then applied pressure with a set of water pump pliers.
That caused the connector to click into it’s socket again and afterwards it worked flawlessly again.
Mind you, some gentle pressure should be enough
Thakyou, that is good to know. So the connector is just pressure-fitted into the bit inside, and evidently my over-zealous SMA screwing has loosened it and pulled it out. That’s the key thing, knowing how this was attached before.
When you say gentle pressure should be enough, you mean just pushing it back exactly the same way it came out, without needing to open it up? I’m worried about applying pressure to try and get it back, and causing the connector to become ripped off the PCB inside.
I wouldn’t try to fit it back with the PCB inside its casing.
That might lead to dislocation of the fitting or breaking the solder connections on the PCB. Without removing you might apply the pressure to the wrong part of the internals.
So remove the PCB ( it fits only one way so there is no risk of not being able to assemble it again) and use the pliers on the SMA connector and it’s fitting ( the recieving side) only.
The water pump pliers enable you to get the pressure in the right direction. Other pliers have an angled pressure surface and that might cause the connector not fitting correctly.
Once fitted again check if the connector is not turning anymore (it shouldn’t). If still turning you need to apply a little more pressure and that should do the trick. Then reassemble again and check if the LNA works as expected.
Understood, makes sense to be sure. I do have some small mole grips I can adjust to ever slightly closer distances, and the flat edges are parallel.
My numbers have been down last year when I previously reworked the setup, and I now suspect I disloged the connector but it remained stuck in place, causing a drop in signal quality. It was this drop which made me believe that the previous rework needed redoing, and then this happened.
I’ll see if Anthony replies and has any additional info too, which I’ll mention back in here for the benefit of anyone searching for this later on.
For now I’m feeding without it and everything is way down, so I do miss it!
As discussed on IRC this was a batch of bad SMA’s from 2016 which we thought we’d seen the last of a few years ago! We are more than happy to repair this for you and we still hold spares for the older LNA’s.
We consider the warranty on the LNA’s lifetime and we’ll repair if we can or replace if we can’t any faulty unit brought to our attention. You can contact us using the links on the following page: Uputronics Contacts
Hi Anthony, thanks for the info. I suspect the ones lurking with the bad SMAs are working great and it’s only when they are reworked that the movement might expose the problem. My unit’s been working great indoors and I didn’t touch it until a few days ago when this happened. I’ll drop you a mail from the contacts page.
In the meantime I think I’ve temporarily repaired this unit using the tips from @tomvdhorst. I used a set of carefully adjusted mole grips to gently push the connector back onto the part on the board. I think if I don’t try to tighten the coax SMA too much it will be okay for now.
