Heathkit IM-5228 User manual

NOTE: Assembly instruction, pages 7 through 19 of the original manual, have been left out.
The VTVM uses a 1.5v “C” size battery for to measure resistance. The battery is inside the VTVM
case and twelve screws need to be removed in order to access it. If the battery is left in the unit for a
long period of time, the battery can discharge and then leak corrosive liquid inside the VTVM.
Circuits using a LM317 adjustable regulator have been employed by others in order to eliminate this
battery. It gets it’s power from the ungrounded side of the 6vac filament transformer used in most
VTVM’s. On this page are a couple of circuits for this purpose.