Repair of Keith Rubow RF Remote transmitter

This (~12/11/17) is the fourth repair of this device – I can’t believe I didn’t record the others.  The $75 device is a 6 button “garage door opener” and USB receiver designed to control music playback software for “tape group” square dances.  It works very well, and with its macro capabilities to insert keystrokes into a window’s stdin, it’s very flexible.  <add lead pic when I get home>

The symptom was that the buttons – especially the most-used Pause/Play, but others as well – were very flaky, often requiring many presses and movements of the whole transmitter to function.  I even swapped the battery (though I was confident the one in place was good) with no improvement.  The most recent was at a C2 lesson session in Crown Point.

When I got home and took it apart, I couldn’t find any bad solder joints.  A continuity check demonstrated this time that the antenna was intermittent.  I had replaced the antenna before, with a much heavier stranded wire, though it only lasted what – a year or 2?

I figured it was solder wicking into the wire inside the insulation that made it fragile, but carefully cutting the insulation off, it was clear that mechanism was not the problem.  It was just ordinary fatigue where the wire exited the case (or very near by).  The heavier wire had 7 strands.

I used a thinner wire this time, but with many more strands, thinking that would be more flexible/forgiving.  I couldn’t find much online to bear that out, though.  I wasn’t very worried about the actual solder connection, but did want to minimize the possibility of solder wicking.  I wouldn’t be surprised if I have to repair this yet again some time, but this joint seems fine.

A quick test showed that the button worked reliably again, so I expect it will work for another couple of years.  For reference, here’s the hank of speaker wire I split it out of.  I’ll change my behavior to leave a longer length coming straight out of the case before I tuck it into my shirt going forward.  Hmm – I wonder if I should make a little strain relief of UV cure resin?  Even if that spanned both halves of the case, I’m sure I could crack it off to change the battery.  There’s a flex version of the Solarez stuff.  Maybe a tapered coating of that?

History

The first failure was a broken antenna connection at a dance in Mike and Shelley’s basement several years ago.  Thankfully Mike had a soldering iron and I was able to fix it there (and continue to dance!).  I think that was also when I started carrying a spare 2032 cell for it – just in case.  That also inspired a decent electronics repair case that lives in the car but gets thrown in the suitcase when we go away without the car (like this trip), though it might have been a year or 2 before I actually made up the case.  Alcohol, glue stick/lighter, duct tape, baling wire in addition to hand tools.  Two sets of those little (3mm?) hex bits merged, and it’s pretty complete.

The second fix was (sourcing and) replacing the Pause/Play button itself.  That didn’t help, as the problem was a broken antenna wire.  I think I put the original switch back in, but in any case did put the original key top back.

Since the switch didn’t fix it, I replaced the antenna with a considerably heavier wire.  That was the wire that had broken this time.

Some place in the repair history, I seem to think there was a problem with a solder joint (probably other than the antenna) that I think was fixed by resoldering that joint.  Sorry I don’t remember any more detail (and didn’t write it up!).

And this repair 12/17, is the most recent (so far).

Gordon’s transmitter failure

I used Gord Whitson’s remote at a basement session in the activity room in Pharr, Texas on 2/2/18, but it was so flaky I eventually gave up and just controlled the music from his laptop’s keyboard.  It felt very much like a broken antenna wire – OK at the beginning, tho only if I held the antenna just so, but it got worse.  It seemed like pressing the wire back toward the case (which I imagined allowed the broken conductors inside the insulation to touch) helped for a while, but soon even with that I couldn’t make it work.

I offered to take a look at it (since I had a soldering iron in my suitcase), and took the transmitter and receiver back to the hotel.  When I opened it up, the PCB was quite different from mine, though the outside looked identical.  His (presumably newer) board had a nice strain relief designed in.  To my surprise and dismay, a careful continuity check failed to show any evidence of an open antenna wire.  Though the range was considerably less than mine, it was much better than when I had used it at the dance, though only if I held the antenna just so.

I had to admit defeat, and returned it unmodified.  Can’t be the wizard every time, I guess. 🙁

Button protector

Not related to the repairs, I feared a little that the transmitter buttons might get jammed pressed and drain the battery when it was stuffed unceremoniously into a bag.  To avoid that, I made some careful measurements, laser cut some acrylic, and heated and bent it to fit around the transmitter.  That new case is a pleasant slide on friction fit.  Thin spacer strips pretty much guarantee the buttons can’t be pressed while the case is in place.  I’m quite pleased with it, and will post a picture as soon as I get home.