ITs been said but I will repeat.
Build it first and test. Insure you have the 4.7K in place on the key jack. Double check wiring.
If you are bench testing before boxing it. Use care to avoid accidental shorts or wires touching
the wrong thing and outside events like ESD (carpet static!). One example seen was taped to
a piece of card board to keep everything from moving around, worked well too.
Use 13.8 volts for testing as its likely a V4 board (discrete transistor audio amp).
If all goes well you may want mods and to pick out what your box is to look like.