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TM 55-4920-412-13&P
(5)
Repeat technique of (1) thru (4) above,
connecting lead to pin connections listed in Table 4-28.
Oscilloscope and frequency counter will indicate within
limits specified. If not, see Troubleshooting Table 4-27.
j.
Digits ONIOFF.
(1)
Set ON-OFF-SIM ONLY to OFF with test
equipment
connected
as
Figure
4-1,
unit
tester
connected.
(2)
Connect digital multimeter leads to 11 pin
3 (+) and COM. Set ON-OFF-SIM ONLY to ON and set
DIGITS ON-OFF to ON.
(3)
Digital multimeter will indicate between 4.5
and 5.5 vdc. If not, see Troubleshooting Table 4-27.
(4)
Hold DIGITS ON/OFF to UP. Digital
multimeter will indicate between -0.5 and +0.5 vdc.
(5)
Disconnect digital multimeter leads from
unit tester.
k.
Analog Set.
(1)
Set ON-OFF-SIM ONLY to OFF.
(2)
Connect test equipment as shown in
Figure 4-1, unit tester connected.
(3)
Set ON-OFF-SIM ONLY to ON.
(4)
Set INTER SELECT switch to 21 and
ANALOG set switch to SLOW and then to FAST while
observing analog INTERFACE MONITOR which will
count at a faster rate and reset after counting to 1827. If
not, see Troubleshooting Table 4-27.
(5)
Set ON-OFF-SIM ONLY to OFF.
Table 4-27. Troubleshooting Rotor Overspeed, Digital Set, Digits, Reset, Display Update and Analog Set Circuits
Trouble
Probable Cause
Remedy
Digital Set B C D output voltage
Digital Set B C D Switch (S 18) TB2.
Replace defective components or
missing on J2
Regulator board (A4).
board (A4). Figures 4-14, FO-6, FO-8.
Rotor Overspeed 127% switch does
Rotor Overspeed 127% switch (S14).
Replace defective components or
not change voltage readings
Regulator board (A4).
board (A4) Figures 4-14, FO-6, FO-8.
Rotor Overspeed 137% switch does
Rotor Overspeed 137% switch (S13).
Replace defective components or
not change voltage readings
Regulator Board (A4).
board (A4). Figures 4-14, FO-6, FO-8.
Rotor Overspeed 142% switch does
Rotor Overspeed 142% switch (S12).
Replace defective components or
not change voltage readings
Regulator Board (A4).
board. Figures 4-14, FO-6, FO-8.
Digits ON/OFF switch does not
Digits ON/OFF switch (S17). Regu-
Replace defective components or
change voltage readings
lator Board (A4).
board. Figures 4-14, FO-6, FO-8.
Faulty Reset switch circuit
Rotor Overspeed switch (S11).
Replace defective components
FO-6.
Faulty Display Update switch
OSC Control Board (A6), Digital Up-
Replace defective components or
circuit
date switch (S16).
board. Figures 4-16, FO-6, FO-10.
Faulty Analog Set switch circuit.
OSC Control Board (A6). B C D
Replace defective components or
Counter Board (AS). Analog Set
boards. See figures 4-16, 4-18, 4-19,
switch (S15) Digital Display Board
FO-10, FO-11, FO-12.
(A12).
Change 2 4-53
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