wrote:

If you remove the battery from Nick's charge pump circuit proposal, you
have what's commonly called a "voltage doubler"... as long as the battery
is there and can accept the current... you have 1.5V regulated by the
battery and no additional regulator is necessary.

I would modify this design by replacing the diode whose anode connects
to ground with a zener rated for 2.5 to 5 volts... if the battery should
open-circuit, the downstream components won't see the 370V spike...

Good idea. Two caps in series might also help with single point failures.

Similar "transformerless stepdown" circuits are used to supply regulated
12VDC to motion detectors.

UL-approved, in plastic boxes. I've heard California is banning
the transformer ilk because of the standby power.

The question of whether the negative terminal of the battery is
connected to an identifiable "common" node in the VOM's internal
circuit is left for further consideration.

That's only a problem for alt.home.repair nitwits, IMO :-)

Nick