On Nov 29, 8:12*am, Bryce wrote:
My v7a vtvm (built by a guy who looks like me but a lot younger)
uses a 1.5v battery

Is there some reason that a zener powered from rectified filament
voltage won't work here?

There aren't satisfactory zeners with voltages under 5V, so
a bandgap reference is more usual. Rectifier, capacitor,
and an LM317 regulator (which uses a bandgap reference and
handles 1.5V output) will do just fine.