You need to alter the jumper pins

These aresituated to the left of the simms and should have on the board J1 and J2 the pin configuration looks like this
a .
b . J1
c .

a .
b . J2
c .

There should be a small plastic cap that slots over theses on each jumper selecter. You must ensure that they are different to those its on at the moment.

the jumper on J1 will either be placed over a pin and b this needs to be changed around so its over b and c . This is the same for J2. Make sure they are the opposite to what they are now.

If you still get the squeak it may be a dry solder joint on the under side of the board for the simms slots.

E mail me if you have any problems and i will send a service diagram. I am very knowledgable on this range as i worked in the Uk as sales manager for 8 years for generalmusic

Darren