MODEL 9-4
Technical Manual
Section 4
Ludlum Measurements, Inc. Page 10
June 2018
Power Supplies
Six voltages are provided for instrument operation.
U108 and associated components generate -90 volts for chamber wall
voltage. The supply will run continually with the instrument off if the jumper
is placed between pins 1 and 2 of JP100. If the operator chooses to have wall
voltage off with the instrument switched off, then the jumper should be
moved to pins 2 and 3 of JP100.
U105 and associated components ge5 volts for the main board
circuits.
U106 provides reg2.5 volt reference.
VR100 pr4.85 volts for the electrometer.
U107 and associated components provides 1.5 volt guard voltage for the
electrometer.
U104 provides meter reference of 0.2 volts.
