[Test-Equipment] Need a DVM Expert

[J C White]

I have several Digital Multimeters that have bad range
switches; I want to use just the digital voltmeter portion
of the unit, which is on a separate pc board, since I can
scale the input as needed.  I understand most of the
operation of the A/D and display, but a couple of the lines
into the DMM portion have me baffled.  Any help would
be appreciated, as I can send diagram of entire DMM or
just the DVM portion I want to use.

Thanks for the read!

John