Wednesday, February 24, 2016

Yaesu FT-2900R PTT Switch Fix

One thing that's bothered me about my otherwise excellent Yaesu FT-2900R radio is how touchy the push-to-talk (PTT) switch is on the included microphone. It's got a very light "touch" to it, which means the least bump or press puts you on the air whether you want to be or not.

It's hard to get it out of the microphone bracket or to hand it to someone else without hitting the switch and doubling over someone while you make unhappy noises about the surprise of the switch getting pressed AGAIN. My wife and daughters often share my station with me when we're checking in to local 2m nets, so being able to hand off the mike is pretty important around here.

Today I finally decided to take matters in hand. Fortunately, Yaesu makes it easy to get into the mike. There are just three screws, two near the bottom of the mike, and one going through the button for the mike bracket (that will be the long screw when you go to put it back together.) Once inside you can see why there's a problem. All the keeps the PTT from getting pressed is a little piece of springy foam that's down near the pivot point for the switch. When you push on the normal part of the switch (or bump into it), you get a lot of mechanical advantage on this little bit of foam, it goes squish, and you're on the air as the plastic tab up top presses into the little microswitch on the microphone's PCB. Not good!

Adding Some Crunch

I took some measurements with a caliper, then headed to the hardware store. In the little drawers of specialty items there are springs (at least in my local hardware stores.) Among them are some small compression springs. The one I chose was a #9 Compression Spring. The specifications are: 0.312 inches OD, 0.047 thick wire, 2 inches long (as sold.) That's 5/16 inches diameter, aka 7.94mm. And 3/64 inches wire, aka 1.19mm. And 2" is about 51mm.

I took this home and clipped a bit off, as you can see in the images. The part I used was about 7/8 inches long, or 22mm. The cut end went over the plastic tab that presses the PTT switch inside the mike, with the flat end resting against the switch body.

If I were the paranoid sort, I'd put a bit of protective tape over the printed circuit board to protect it from the spring. However, there's nothing for the spring to short to even if it does wear through the solder mask on the trace it lays over. So I just left it alone.

After reassembly, my microphone has a nice crunchy feel to it, and it takes just the right amount of force to close the PTT switch now. The force resisting closure is up at the top of the switch where it belongs, now, so even this little spring does the job.

I hope this helps some of you out there, because I've heard a lot of other FT-2900R owners with the same complaint about the PTT switch that I've had.