TM 11-5820-890-30-4
12-24. TROUBLESHOOTING FLOWCHARTS.
The following flowcharts contain the troubleshooting procedures used to fault isolate an RCU to a bad module.
Observe the following when using a flowchart:
a.
b.
c.
d.
e.
f.
g.
h.
Do not start a flowchart unless directed to it by another troubleshooting flowchart or by the operational
check.
Read through each flowchart block and the following diamond before performing any actions.
Do not change RCU or test equipment switch settings unless directed to do so by the flowchart or the
test setup diagram.
Refer to Chapter 3 for information on the reference fixture and the test adapter.
The logic levels in the RCU are as follows:
logic 0 = -0.7 to 1.7 V dc
logic 1 = 3.8 to 6.4 V dc
negative logic 1 = -5.0 to -7.25 V dc
The logic 1 level given is typical for a digital output. A good logic 1 level may be as low as 5.0 V dc.
The test responses at some test points are not seen immediately. Check the probe location and per-
form the test again to verify a faulty result.
The reference fixture and REF RT are part of Maintenance Group OA-9297/GRC.
Some of the more common frequencies are as follows:
Frequency
Period
Pulse Width
75 Hz
150 Hz
640 Hz
1 kHz
1.2 kHz
2.4 kHZ
2.88 kHz
4.8 kHz
8 kHz
16 kHz
32 kHz
40 kHz
192 kHz
320 kHz
640 kHz
3.2 MHz
13 ms
6.7 ms
1.6 ms
1.0 ms
0.83 ms
0.42 ms
0.34 ms
0.21 ms
125 µs
62.5 µs
31.25 µs
25 µs
5.2 µs
3.1 µs
1.6 µs
0.31 µs
6.7 ms
3.35 ms
0.78 ms
0.50 ms
0.42 ms
0.21 ms
0.17 ms
0.10 ms
63 µs
31 µs
15.6 µs
12.5 µs
2.6 µs
1.6 µs
0.78 µs
0.16 µs
12-45
