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A modification for the Yaesu FT290R microphone
Many of us use the FT290 as a prime mover on the microwave bands. Quite often during initial line up testing one is asked to transmit a continuous carrier for perhaps some minutes while the far end searches for your signal. This usually entails holding the PTT or key down for this period. A good strong elastic band is useful for this purpose but can either get forgotten, or worse...snap!

The Yaesu YM-47 microphone has a slide switch on its rear which allows one to "lock" the up/down buttons. I like many others no doubt, never use this function and thus decided to use the slide switch for a PTT function.

Unplug the microphone from the rig and take out the two screws which hold the microphone casing together. Carefully separate the two parts of the microphone casing and remove the pcb with the microphone insert attached from the casing. Don't loose the up/down buttons or the PTT lever in the process, but note that the up/down switches themselves come away with the pcb. With the microphone insert facing you, locate the pcb track shown in the drawing. (Not all the pcb tracks are shown for clarity.) Carefully cut the pcb track and add the 2 wire links shown, using insulated wire. Re-assemble the microphone and there you have it. The up/down function is retained but the slide switch will now work in parallel with the PTT switch.

Slide the switch to the "on" position and you can send continuous carrier for as long as the other station needs it while you can get on with your ham sandwich!

The usual disclaimers regarding modification of equipment apply.