I tried this thing:
Connect the 12V from the power input to the module input, adjust the pot for 20V to 24V at the output and connect your PA power connector to the output of the module.
There is an "Enable" pin which I did not use. The data sheet says it should be connected to GND in order to shut down the converter:
Did not measure the volatge drop when disabled, or if the module passes the input voltage to the output when disabled.
You will need about 1A at output so almost 2A at the input, which adds to your regular 0.5A currect draw of the rest of the board, so a 12V/3A power supply is required.
Good luck,
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Ion
VA3NOI