TM 11-6625-524-14-4
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
connection (s). Use the DC multimeter set to 1X ohms for continuity checks.
FEEDBACK, LINEARIZING AND CALIBRATION CONTROL NETWORK
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.
d. R e c o n n e c t the oscillator to the probe. C o n n e c t the oscilloscope to amplifier
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.
h. Disconnect the equipment as shown in figure 5-1.
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.
NOTE
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
source.
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
direction.
S w i t c h to the 0.03V full scale range position.
The voltmeter should recover
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:
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