TM 11-5820-801-30
Section III. TROUBLESHOOTING
charts differ in monitor checking procedures because of
3-6. Fault Isolation
time delays encountered in start-up procedures while
a. Circuits Covered in Diagnostic Flow Charts.
vacuum and temperature equilibriums are being
Troubleshooting procedures as detailed in the diagnostic
established The time required for Modules 2AI and 2A2
flow charts (fig 3-6 and 3-7) are designed to locate and
to reach their operating temperatures is less than that
isolate a fault to a replaceable module, subassembly, or
required for Module 2A3 to reach its environmental
component in the signal amplification circuits and the
conditions, therefore, when Module 2A3 is ready to
temperature and pressure (vacuum) monitor and control
operate the other two modules are also ready to operate
circuits. The faulty item shall be removed from the
(2) Chart Sections. The diagnostic procedure is
system and replaced with a spare These circuits
conveniently divided into two sections the first section
comprise Amplifier, Parametric AM-6602/MSC-46(V).
utili7es system monitors and a multimeter for fault
The redundancy kit, Unit 3, is not included
isolation, the second section utilizes RF signal generation
b. Unit 3 Subassembles. The redundancy kit, Unit 3,
and detection equipment for evaluating system operation
is not directly involved in the troubleshooting procedure
and for isolating faults RF tests should not be made until
because it does not affect the normal operation of the
the monitors have been checked Since the two charts
parametric amplifier If, however, a fault is isolated to IMI
differ only in the monitor checking procedures but are the
or IM3, the corresponding 3AI meters (para 3-3a) may be
same for RF test procedures, figure 3-7 refers to figure
faulty because 3A1 meters are operated in parallel with
the Unit I meters. When a IMI or IM3 fault is indicated,
(3) Systematic Troubleshooting. The direct-
remove the cable at 3AIJI. If the fault remains, it is in Unit
support maintenance technician should always use a
I. If the fault clears, it is in 3AI, then refer to paragraph 3-
diagnostic flow chart for troubleshooting so that a
3a for procedure. Waveguide assemblies 3A2, 3A3, 3A4,
systematic method of fault isolation is maintained. Spot
3A5, 3A6, 3A7, 3A8, 3A9, 3A10, 3AII and 3 A 12 are
checking at random of the several circuits may or may
highly unlikely to cause RF faults unless waveguide
not isolate the cause of trouble and is therefore not
interconnections are not tight or unless the waveguides
recommended
have become physically deformed Refer to organizational
(4) Chart Use. The diagnostic flow charts (fig 3-
maintenance checks and services for interconnection
6 and 3-7) are designed to test a module, subassembly,
information. Waveguide assemblies or waveguide runs
or component sufficiently to verify that the item is faulty
(3A2, 3A4, 3A5, 3A6; 3A2, 3A9, 3A5, 3A10; 3A3, 3A8,
before it is removed and replaced The charts assume
3A5, 3A7, 3A3, 3A12, 3A5, 3AI I) can be measured for
that only one fault has occurred and provide the method
insertion loss by the procedure given in paragraph 3-8.
of isolating and correcting the fault The technician enters
Insertion loss per assembly shall be 0. I1 dB or less If a
the chart at the upper left comer START and reads
failure occurs in the drive motor or indicator section of
from left to right along the top line only, verifying the
Waveguide Switch 3A2 or 3A3, 3AI indicator DSI, DS3,
monitor indications or performing the required test until a
or DS2, DS4 (fig 2-25 and 3-4) will not switch when the
fault (no-go condition) is encountered If a fault is
unlit half of the 3 A I S I pushbutton switch (CIIANNEL
discovered he reads down the branch line (top to bottom)
SELECT) is depressed Remove and replace 3A2 or 3A3
performing the tests as indicated until he isolates and
Refer to paragraph 3-3h for checkout of 3AISI.
corrects the fault This is usually the removal and
c Diagnostic Flow Charts (fig 3-6 and 3-7)
replacement (R/R) of a component, subassembly, or
(1) Initial Conditions. Diagnostic flow charts are
module but may be a voltage or attenuator adjustment.
presented for two sets of initial conditions: normal (fig. 3-
lie then returns to the top line where he discovered the
6) and initial start-up (fig. 3-7). Figure 3-6 applies when
fault and continues to read and check from left to right If
the system is in operation (one channel operating and
no faults are encountered along the top line of the flow
one channel in standby) as will normally be the case For
chart, the equipment is satisfactory and no further testing
this condition the two Unit 1 circuit breakers and power
shall be made. No branch (down) line of the flow chart
switches (MAIN, PARAMP and REFRIG POWER) are
shall be checked unless a no-go condition has been
set to ON and Module 2A3 is (or had been) at its ambient
indicated in the top line The primary requirement of the
environmental conditions internal temperature of 20 +
system is to provide 29.5 + 1 dB gain over the 7.5 + 0.25
2K and internal pressure of 40 millitorr or less. Modules
GHz frequency range. All other requirements are
2A2 and 2Ai will be at their normal elevated
secondary.
temperatures. Figure 3-7 applies when Module 2A3 is at
(5) Items Not Checked By Chart. The
room temperature and room pressure and the two circuit
diagnostic flow charts assume that any malfunction is in
breakers and switch (MAIN, PARAMP, REFRIG
a replaceable
POWER) are set to OFF. This condition can occur when
Module 2A3 has been replaced, or Unit 4 has been out of
operation, or when primary power has been shut off for
an hour or more. Figure 3-7 could be used also during
preliminary adjustment at initial installation The two
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