PTT won't transmit

[CAflyer2020]

I'd appreciate any troubleshooting ideas....

When I push the copilot PTT switch (Two wires), I don't get a side tone, other aircraft / ATC can't hear me (I do not get "carrier no voice"), and there is no voice transmission through the intercom. The T light in each radio lights up and I do hear a click in the headset.

Have tried different headsets (all work on pilot side). PTT works. Both radios have same issue and work fine, including intercom, from pilot's side. Have tried intercom without PTT and copilot side doesn't work either.

Equipment consists of 2 KX 155 TSOs, KMA 24 audio panel, Sigtronics SPA 400 TSO, and new wiring.

 

[Jdm]

Maybe try cleaning it with electrical contact cleaner while actuating the switch. Or you could use an ohm meter to see if it’s sticking. Check the wiring really well to see if anything is broken. Replace the switch if needed. It’s an easy swap

 

[CAflyer2020]

Thanks Jdm. Have already replaced switch - no joy. Looking deeper for the root cause.

 

[3393RP]

You're going to get half a dozen answers that probably won't fix the problem, especially if you don't know anything about radios and how headset jacks are wired.

How new is your new wiring? Why aren't you discussing this with the person that installed the wiring?

 

[flyingron]

Are you sure it's only two wires? Some of the PTT switches actually are double throw which shorts the mic input when not depressed.

 

[AKBill]

Mic jack as I remember has 3 wires, 2 for the push to talk and 1 for the mic audio.

 

[JAWS]

Sigtronics has a good install and troubleshooting guide. Google can be your friend.

 

[Snowmass]

Maybe try cleaning it with electrical contact cleaner while actuating the switch. Or you could use an ohm meter to see if it’s sticking. Check the wiring really well to see if anything is broken. Replace the switch if needed. It’s an easy swap

YES! But use a lubricating cleaner not just straight cleaner. Even WD-40 will often work.

Switches mechanical devices and need regular lubrication and this includes landing gear switches.