Install an alkaline AA cell in place of BA-24. Of course this will not fit in the battery holder so it will be necessary to solder lead wires on the AA cell and then solder to the holder.
Since the BA-24 was 1.35V and the alkaline cell is 1.5V it will be necessary to change three resistors:
- R143 from 3.48kohm to 4.99kohm
- R113 from 135kohm to 150kohm
- R155 from 1.5kohm to 1.67kohm
The BA-24 cell is used for Ohms function only and can be removed completely if only Volts, Amps, and Coulombs are being measured.
On the other hand, if the Ohms mode is functional, it can also serve as a low constant-current source, 10uA to 1pA in decade steps.