I recently received a Macintosh IIx that had its soldered PRAM batteries removed.
I believe battery B2 provides the voltage for the power supply to start up once the power button is pressed.
Since I didn't have any 1/2 AA batteries/holders I soldered a 9v battery to B2. The Mac did not come on when the power button was pressed.
After this I removed the 9v battery and replaced it with a AA battery holder, supplying 3v altogether. The Mac did not start in this configuration.
What am I missing? Do batteries need to be present in B1 and B2 for the Mac to start?
I'm sure a similar technique was shown inside a Macintosh II on an episode of Jason's Macintosh Museum.