From what you've measured so far, it sounds likely there is an open circuit PCB track somewhere, or possibly a problem with the edge connector.
The discreet components don't readily fail in this situation, so focus more on checking track continuity to begin with.
I don't have the schematic of the A601, but it's practically the same as the A501, schematic
here. The scan is pretty crap and you can't read pin numbers, so also refer to the RTC schematics of the
A500+ and the
A2000 which both operate the same way.
There should be 5V on pin 18 (Vcc) of the RTC when the computer is running. Pin 9 is ground. About 3.6V when it's off and the RTC is running from battery.
I've written a guide on
repairing the Amiga RTC which is mainly directed towards the A4000D, but might be of some use.
