Hi Malcolm,
The main spring is probably broken or has come off the spindle - do not try to do a DIY repair as the spring is under enormous tension and can cause severe injury if it is suddenly released by opening the spring box.
I have a contact for a (the?) Sydney gramophone repairer - I'll send it to you directly. If the gramophone has never been serviced it may be worth having a full job done on it. The diaphragm on the playing head of most gramophones only has a 20-30 year life expectancy - you'll be stunned at the difference a new one makes.
I also have a wind-up gramophone with a Thorens turntable - it dates from 1915.
Cheers
Tony