reverse polarity im afraid
the red wire needs to be in the right hand socket in the plug and black in centre not as normal futaba centre pin is red (positive volts )
ask me how i found out too
cant tell whether handset is dead or not i do have a ko helios ( scruffy )one with good internals id part with if you have killed yours
sorry to be bearer of bad tidings
pm me for more help if necc
dave fid