TM 11-5841-287-30
Table 3-2. Encoder and Data Link Control Troubleshooting-Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 14
Test 2A5 (para 3-29), 2A9 (para 3-31), 2A7 (para 3-30), 2A3 (para 3-28), then 2A2 (para 3-27) Perform steps 2 and 3 of Malfunction 7
Replace defective circuit card.
Step 15
Set oscilloscope to 0 2 V per division and 50 microseconds per division Connect scope to 2A17J1-S Place data lhnk control POWER
switch to XMT and press DOWNLINK BITE switch
(a) A pattern of pulses approximately 0 8 volts m amplitude referenced to ground, pulse width approximately 6 microseconds IS observed Test
2A9 (para 3-31), 2A7 (para 3-30), then 2A2 (para 3-27)
Perform steps 2 and 3 of Malfunction 7
(b) The pattern described m step 15(a) does not appear at any timune Perform step 16
Step 16
With oscilloscope observe digital activity at 2A19XA17-28 A pulse tram of normal logic level (O+ 0 5 V low level and 3 5 + 1 5 V high
level) with pulse widths of approximately 6 microseconds should be observed
(a) Correct pulse levels and widths are present, perform step 17
(b) Correct pulses not present Test 2A7 (para 3-30), then 2A6 (para 3-39) Perform steps 2 and 3 of Malfunction 7
Replace defective circuit card
Step 17
Check 2A19XA17-25 for a high logic level You may have to restart BITE as described in step 12
(a) Signal always low or does not reach a true high level Test 2A16 (para 3-36), then 2A17 (para 3-37) Perform steps 2 and 3 of Malfunction 7
Replace defective circuit card
(b) The signal alternates high and low during BITE test Test 2A 17 (para 3-37) Perform steps 2 and 3 of Malfunction 7
Replace defective crcuit card (para 3-11)
Step 18
Test 2A6 (para 3-29), then 2A7 (para 3-30) Perform steps 2 and 3 of Malfunction 7
Replace defective circuit card
Step 19
Test 2A5 (para 3-29), then 2A7 (para 3-30) Perform steps 2 and 3 of Malfunction 7
Replace defective circult card
Step 20
With DVM, measure voltage at 2A2J1- 1 (2A2J1-22 ground)
(a) 40
0 1 volts Perform step21
(b) Any other voltage Replace2A2(para3-11)
Step 21
With oscilloscope set to 0 2 V per division and 50 microseconds per division, observe 2A17J1-17 Place data link control POWER
switch to XMT and press DOWNLINK BITE switch
(a) A pattern of pulses 0 4 V m amplitude referenced to ground each pulse approximately 13 microseconds wide observed Test 2A9 (para 3-
31), 2A7(para 3-30), then 2A2 (para 3-27) Perform steps 2 and 3 of Malfunction 7
Replace defective circuit card
(b) Above pulses not present Perform step 22
Step 22
With oscilloscope observe digital activity at 2A19XA17-26 A pulse tram of normal logic levels (0 + 0 5 V low level and 3 5 + 1 5 V high
level) with pulse widths of approximately 13 microseconds should be observed
(a) Correct pulse levels and widths are present Perform step 23
(b) Correct pulses not present Test 2A7, 2A6, 2A5, 2A17 in order Perform steps 2 and 3 of Malfunction 7
Step 23
Check 2A19XA17-35 and - 19 for a logic high while BITE is in process
(a) High not present (either or both points low) Test 2A16, then 2A17 Perform steps 2 and 3 of Malfunction 7 Replace defective circuit card
(b) Both points high Test 2A17 Perform steps 2 and 3 of Malfunction 7
NOTE
Make sure power is off when removing and replacing circuit boards.
10. AIRBORNE OR DOWNLINK BITE CYCLE ABNORMAL OR BITE CYCLE NORMAL EXCEPT FAILS TO STAY IN BITE WHEN IN DOWNLINK
BITE IN XMT
Step 1 Check 2A19XA16-37 for 0 + 0 5 volt
(b) Approximately 20 Vdc Turn power OFF Trace wiring from 2A19XA16P1-37 through 2A19J2-12, 2J1-D to encoder control 3J1-D to 3S1B-3
Repair defective wiring or replace 3S1 as necessary
Step2 For all other abnormal BITE cycles Test in order-2All (para 3-32), 2A13 (para 3-34a through 3-34c(8)), 2A12 (para 3-3), 2A14 (para 3-35),
2A7 (para 3-30), 2A5 (para 3-29), 2A6 (para 3-29), 2A9 (para 3-31), 2A16 (para 3-36), 2A3 (para 3-28), 2A4 (para 3-28), 2A17 (para 3-37)
Replace connector 2A19 (para 3-15)
11. NO ERROR DETECTED, BUT ENCODER DOES NOT OPERATE PROPERLY WHEN INSTALLED IN AIRCRAFT
Step 1 If you have no additional information, test in following order
(a) 2A7 (para 3-30), 2A14 (para 3-35), 2All (para 3-32), 2A5 (para 3-29), 2A6 (para 3-29), 2A16 (para 3-36), 2A17 (para 3-37), 2A13 (para 3-
34), 2A12 (para 3-33), 2A3 (para 3-28), 2A4 (para 3-28), 2A9 (para 3-31), 2A2 (para 3-27) Replace defective circuit card (para 3-11)
(b) Perform continuity checks for chassis wiring Repair wiring as necessary
(c) Check connector assembly 2A 19 by replacement (para 3-15)
(d) If additional information is available, test as Is appropriate,
Change 1 3-10
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