When the Push To Talk (PTT) switch on an ICOM HM-133 microphone wears out, the switch can be replaced instead of buying an entire new microphone. Replacing the switch is easy and will save a great deal of money. Below are the part numbers and a step by step guide to walk you through repairing the HM-133 microphone PTT switch.
When the PTT in my HM-133 stopped working, I was initially able to squeeze the PTT key harder to make it work. This made the switch work better, but it would wear out my hands during a long conversation. Squeezing the PTT harder only helped for a few weeks. I tried cutting paper into small squares and using the pieces as shims. The shims went between the key you press and the switch inside to push it a little farther. Eventually the PTT switch stopped working altogether, rendering my HM-133 and its IC-208H as useless.
I was going to pick up a replacement at the local Ham Radio Outlet, but the HM-133 was about $80. No disrespect to the guys at HRO, but I suspected I could fix it more cost effectively. As it turned out, I was able to fix my microphone for $0.29 by simply replacing the switch instead. The difficult part was figuring out an exact replacement switch that would fit the microphone circuit board. After a time-consuming search, I found an exact replacement switch for the HM-133.
PTT Switch Part Number
I found the following switch part number fits my HM-133:
- C&K PTS645VK39-2 LFS (manufacturer’s part number)
- Digikey CKN10053-ND (I purchased mine from Digikey)
Fixing the HM-133
Assuming you know how to solder, replacing the PTT switch inside the HM-133 is easy. All you need a small Philips screwdriver and the appropriate soldering equipment.
- Align and insert circuit board into microphone body. It should easily go into place.
- Insert and tighten the small screws into the holes labeled 1, 2, and 3. Do not over tighten the screws.
- If the gray rubbery piece came off earlier, put it back in place now.
- Insert the plastic key back into the body. Its axle must go into the hole at the bottom and the key portion should cradle the gray rubbery piece. I did this by performing a twisting operation on the PTT key as I rocked the axle into the pivot hole.
- The back of the HM-133 microphone has a catch that forms a hinge. Align the two halves at the top and close the microphone in a clam-shell motion as shown in the picture.
- Insert and tighten the two screws that hold the body together. Do not over tighten the screws.
- Align and insert the cable into the bottom of the microphone.
Fixing the ICOM HM-133 microphone is an inexpensive, straight forward repair that can be completed in about a half an hour once you receive the new switch. For me, it was difficult finding the correct replacement switch part numbers. Now that I have published the part numbers, the task should not only be easy, but economical too.