Mmm.. you know what? An even safer way to repair this kind of fault would be to use an axial lead 1A fuse in place of the jumper wire.

A minor fault with the original design, is that the fuse on the +12V wire generally doesn't seem to protect the circuit -- the PCB ground trace burns out before the fuse blows.

So shunting the new ground wire using a fuse rather than plain wire might protect things better.

I'll try and remember that for next time. I even have some of the right style of fuses here -- long skinny things with lead wires on them, which look very much like traditional resistors.

Cheers