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TM 55-4920-412-13&P
c.
Logic P/S, SDC FAIL, P/S CONT PILOTS, and
COPILOTS switch circuits.
(1)
Connect digital multimeter leads to J2 pin I
(+) and SDC COMM on unit tester.
(2)
Set ON-OFF-SIM ONLY to ON.
(3)
Set Logic P/S switch to 1. Digital
multimeter will indicate between +13 and +17 vdc. If not,
see Troubleshooting Table 4-21.
(4)
Set ON-OFF-SIM ONLY to OFF.
(5)
Disconnect test leads from J2 pin 1 and
reconnect to 19 pin 19.
(6)
Set ON-OFF-SIM ONLY to ON.
(7)Set P/S CONTROL to FULLY CW position. Digital
multimeter will indicate between +4.5 and +5.5 vdc. If
not, see Troubleshooting Table 4-21.
(8)
Set ON-OFF-SIM ONLY to OFF.
(9)
Repeat techniques of (2) thru (4) above at
unit tester switch setting and pin connections listed in
Table 4-22. Digital multimeter will indicate within limits
specified. If not, see Troubleshooting Table 4-21.
NOTE
In Table 4-22, INTER CAL SELECT
switch must be set to 15 for pin
connection J2 pin 41 and to 19 for pin
connection J2 pin 43.
(10)
Disconnect
digital
multimeter
from
equipment setup.
(11)
Connect jumper between J3 pin 26 and J3
pin 27.
(12)
Connect digital multimeter positive lead to
J3 pin 93 and negative lead to J3 pin 26.
(13)
Set ON-OFF-SIM ONLY to ON. Digital
multimeter will indicate between 7.5 and 11.5 vac. If not,
see Troubleshooting Table 4-21.
(14)
Set ON-OFF-SIM ONLY switch to OFF.
NOTE
Perform
Logic
P/S
checks
in
Paragraph c before Troubleshooting
Logic Power Supply Board (A3).
Table 4-21. Troubleshooting Logic P/S. SDC Fail, P/S Cont., Pilots, and Copilots Switch Circuits
NOTE
Install extender board before troubleshooting
Trouble
Probable Cause
Remedy
Placing Logic P/S switch in 1 or 2
Logic Power Supply (A3), Logic
Replace defective components or
Positions does not change voltage
Power Supply Switch (S9).
circuit board (A3), see Figures 4-13,
readings
FO-6, FO-7.
SDC Fail switch indicates open
Wiring or SDC Fail Switch (S10).
Replace defective components or
circuit
wiring, see Fig. FO-6.
Placing P/S Cont. in Remote or
OSC Control Board (A6), Internal
Replace defective components or
normal positions does not change
Power Supply Switch (S8).
circuit board (A6). See Figures 4-16,
voltage readings
FO-6, FO-10.
Rotating Pilots Control to FULLY
Pot (R3), Logic Power Supply (A3),
Replace defective components or
CW position does not vary voltage
Regulator Board (A4).
boards. Figures 4-13, 4-14, FO-6,
voltage
FO-7, FO-8.
4-42 Change 2
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