Boli46, I will forward the thread to my friend in Sydney. Sometimes the open circuit is caused by a failure of the lead out wires and he can effect a repair. Your AGA driver is a Lansing 801 or 801b, very worthy of repair. If all else fails a more modern Altec diaphragm can be fitted.

To all, the prewar Lansing and RCA drivers used a 2.5" sixteen thread per inch coupling, referred to as the "firehose" coupling in the old days. Not sure if this was literally true. The Vitavox S2 was similar, though it used a different cutting angle on the threads, whose name has escaped me.