No joy yet.
None of the caps are shorting. Without the STA fitted, the resistance from the output pads of the STA to the speaker terminals measured about 13k. I fitted the new STA but there's no sound. It's drawing about 50mA and the STA is getting slightly warm which all seems to be as it should. I jumpered the input pins to check the DC offset on the speaker terminals but it's measuring zero even when I adjust the pot.
Is it likely to be the TC2001? Or something else?
EDIT: I've got a another (working) AMP11 here and it draws about 110mA when it's not playing, so presumably the fact that the damaged one is only drawing 50mA is significant.