[G4] No Sound from External Speakers

[Alan Kidner]

I had a very croaky internal speaker in my G4 (MDD / FW 800 model), 
which I took the opportunity of removing during a recent PSU 
replacement.  I always use external speakers and assumed that the 
internal one would therefore be redundant.  However, now it is removed 
the external speakers have stopped working!

Does anyone know a simple way to make the external speakers work again?  
For example, would it be safe to just put a jumper over the two pins of 
the internal speaker connection on the motherboard?