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TM 11-5895-1123-34
panel to the rack and carefully pull the panel away from
the rack.
receptacle near the center of the VR monitor panel.
c. Remove the four screws retaining the plastic
The multimeter function should be set to AC and the
protective cover on the rear of the panel to the support
range to 200 for this measurement.  If voltage is not
posts and remove the cover.
present at the receptacle or is outside the range of 115
d. Tag and remove the six ring tongue terminals
4.6 volts, check the voltage regulator unit which is
from the terminal board (TB1) which hold the wires going
mounted behind the data patch panel at location A8 in
into the rack and remove the panel.
rack 6.
e. Reinstall the six screws to TB1 to prevent losing
(8) If the voltage measured at the ac receptacle is
them.
normal and the VR monitor reading is not, follow the VR
3-29. Maintenance of Voltage Regulator Monitor Panel
monitor meter-relay calibration procedure in paragraph
SMD936692
329c below.
b. VR Fault Indicator Circuit Check Out and Fault
WARNING
Isolation.
Several tests and adjustments called for
(1) Review and repeat the initial conditions and
on the VR monitor panel are to be
checks outlined in 329a above.
performed with the panel removed from
(2) To properly check out all aspects of the VR fault
the rack but the wiring still connected, as
indicator circuits, normal regulated ac voltage should be
the panel must be energized for the
indicated by the VR monitor.
tests and adjustments to be performed.
(3) To check undervoltage fault sensing, turn the
Two persons should be present during
adjustment screw for the lower voltage limit cursor on the
this work, so that one person may firmly
VR monitor clockwise until the cursor meets the black
hold the panel to prevent it from moving
indicator  needle.
The  indicator  needle  should
around while in the energized condition.
electronically latch to the cursor contact and the FAULT
When energized, the VR monitor panel
lamp should illuminate.
contains voltages dangerous to life.
(4) Return the lower limit cursor to the 110 volt
a. Initial Conditions and Checks.
position (or lower) and actuate the fault reset switch to
(1) Apply power to racks 4, 5, and 6.
break the latch. The black indicator needle should break
(2) Alarm monitor panel in rack 4 must be turned on,
free and resume indicating normal voltage.
as it is the source 24 volts for the Voltage Regulator (VR)
The FAULT lamp should extinguish.
monitor fault alarm circuit.
(5)
Test the upper voltage limit sensor functions in
(3) Set red upper and lower limit cursors on the VR
the same manner as in (3) and (4) above except that the
monitor meter to 120 and 110 volts, respectively.
upper limit cursor adjustment screw is to be turned
These cursors are set by the upper two of the three
counterclockwise for the cursor to meet the indicator
screws which pass through the meter window.
needle. Return the upper cursor to 120 volts after the
NOTE
test and actuate the FAULT reset to break the latch and
The lower screw at the meter window is
extinguish the FAULT lamp.
the  meter  calibration  adjustment.
(6) If the indicator needle fails to latch to both the
Access to this screw is limited by a
cursors in the tests of (3) through (5) above, the problem
cover  plate  to  prevent  accidental
probably lies in the 24 volt circuit to the VR monitor, but
alteration of the meter calibration.
may be due to a defective meter-relay unit.  If latch
(4) Actuate the FAULT reset switch to clear any
failure occurred at only one voltage limit, the most
initial fault indication.
probable cause is a defective meter-relay unit, but may
(5) If fault lamp has not been observed to illuminate,
be in the 24volt wiring.
push to test. Replace bulb if necessary.
c. VR Monitor Meter Relay Calibration Procedure.
(6) The normal voltage indicated by the VR monitor
(1) To calibrate the VR monitor meter, normal
meter is between 110 and 120 volts. The meter indicator
output of the voltage regulator (115 +4.6 vac) must be
needle should not be latched to either of the red
present at the monitor meter.  It is convenient to
voltagelimit cursors which are set to 110 and 120 volts.
measure this voltage at the regulated 115 volt ac
(7) If the indicator needle is latched to either red
receptacle near the center of the VR monitor panel.
limitcursor and the latching cannot be permanently
Use the Fluke 8000A Digital Multimeter for the
broken by momentary actuation of the fault reset switch,
measurement and make note of the reading.
use the Fluke 8000A Digital Multimeter (multimeter) to
(2) If the VR monitor voltage indication is within 2
measure the voltage present at ac
volts of the Fluke 8000A multimeter reading, recalibration
should not be attempted.
(3) If it is determined that the monitor meter requires
calibration, or if it is desired to attempt
3-50

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