| shown here the connections on the board for the
battery and external psu.
normally, the batteries are sealed inside
the unit as three AA nickel cadmium cells. these are recharged when the
external 9v psu is connected.
normally, the rechargeable cells are dead, and possibly leaking. you
can remove these cells and make up a new battery pack. if you do, it is
advisable to use nickel cadmium rather than metal hydride if you plan to
use the original charger.
an alternative is to remove the cells altogether and just use the
external psu. this is what ive done. but beware, if you do this,
do not use the original 9v psu because the cells act as a load
when connected. without the cells use a lower voltage. i found 5 volts
to be fine.
also, the mini jack power plug requires +ve tip.