POWER AND RANGE SWITCHES
Should a switch be suspected as being faulty, check the applicable contacts and
w i p e r ( s ) of the questionable switch section(s) for contact continuity. Also check
t h e wiring continuity between the suspected switch section (s) and their circuit
a. W i t h the voltmeter properly shielded (see paragraph 5-2) verify that all
l i n k s are connected to their original circuit board connections.
b. V e r i f y the RANGE switch is set to the 0.001V full scale position.
c. D i s c o n n e c t the oscillator from the probe. Adjust the SET REF control (volt-
meter) for a meter reading centered about the SET REF line.
board terminal (3TP7). With 1mV applied to the probe, measure the waveshape and com-
pare to that as shown on the schematic diagram, figure F0-1. Should the level
g r e a t l y exceed that as shown, the network is probably faulty.
e . The following procedure may be used to troubleshoot the network:
f. Check the resistor and thermistor values, diode forward and reverse re-
sistances and the continuity of the network. Use a DC multimeter set to ohms.
g. Check the probe for resistance measurements as shown in. Table 5-1. Use the DC
multimeter set to ohms.
SECTION III MAINTENANCE
PROBE AND DIODE CARTRIDGE
T h e probe and diode cartridge are factory sealed and their disassembly is not re-
c o m m e n d e d . If defective, replace.
Warranty on the probe and diode cartridge is void if tampered with.
I f the voltmeter fails to respond to RF signals and all other checks of the trouble
shooting sections have been made, t h e probe and/or diode cartridge may be at fault.
U s e the following procedure to verify the probe and diode cartridge's condition:
W i t h the voltmeter either in its cabinet or properly shielded (see paragraph 5-2)
e n e r g i z e and switch to the 0.001V full scale range position. Attach the probe,
terminate with the 50-ohm termination adapter but do not connect to a signal
R o t a t e the SET REF control fully clock-wise, a normally operating voltmeter will
read between 50% and 100% of full scale. Disconnect the probe from the voltmeter,
a normal response is for the meter indicator to drift off-scale in either
S w i t c h to the 0.03V full scale range position.
r a p i d l y with the indicator returning to the SET REF position. These tests will
v e r i f y that the voltmeter is operating normally. The probe and/or probe diode
c a r t r i d g e is then at fault and should be individually tested as follows: