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TM 55-4920-412-13&P
NOTE
Perform
logic
P/S
checks
in
Paragraph c before Troubleshooting
Regulator Board (A4).
e.
Regulator Board A4.
(1)
Connect test equipment as
shown in
Figure 4-1 with unit tester connected and Set ON-OFF-
SIM ONLY to OFF.
(2)
Connect digital multimeter leads between
J6 pin 26 and COM.
(3)
Set ON-OFF-SIM ONLY to ON.
(4)
Digital multimeter will indicate between
+9.5 and +10.5 vdc. If not, see Troubleshooting Table 4-
24.
(5)
Set ON-OFF-SIM ONLY to OFF.
(6)
Disconnect digital multimeter lead from J6
pin 26 and reconnect J6 pin 27.
(7)
Set ON-OFF-SIM ONLY to ON.
(8)
Digital multimeter will indicate between
-9.5 and -10.5 vdc. If not, see Troubleshooting Table
4-24.
(9)
Set ON-OFF-SIM ONLY to OFF.
(10)
Disconnect digital multimeter lead from J6
pin 27 and reconnect to J9 pin 37. Observe that CLOCK
INHIBIT is set to ANA position.
(11)
Set ON-OFF-SIM ONLY to ON. Digital
multimeter will indicate between +4.5 and +5.5 vdc. If
not, see Troubleshooting Table 4-24.
(12)
Set CLOCK INHIBIT to DIG position.
Digital multimeter will indicate between -0.5 and +0.5
vdc.
(13)
Set ON-OFF-SIM ONLY to OFF.
NOTE
CDU and SDC when tested provide
voltage inputs to unit tester for light
circuits listed below. Troubleshoot
as applicable.
Table 4-24. Troubleshooting Regulator Board (A4)
NOTE
Before performing troubleshooting, remove regulator board (A4) and reconnect
using extender board.
Trouble
Probable Cause
Remedy
+10 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
Regulator board (A4).
boards. See figs. 4-13, 4-14, FO-7,
FO-8.
-10 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
Regulator board (A4).
boards. See figs. 4-13, 4-14, FO-7,
FO-8.
5 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
Regulator board (A4).
boards. See figs. 4-13, 4-14, FO-7,
FO-8.
+15.5 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
boards. See figs. 4-13, FO-7.
± 15.5 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
boards. See figs. 4-13, FO-7.
8 vdc output low or missing
Logic Power Supply Board (A3).
Replace defective components or
boards. See figs. 4-13, FO-7.
Change 2 4-49
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