TM 11-5820-890-30-4
2-30. TROUBLESHOOTING FLOWCHARTS.
The following flowcharts contain the troubleshooting procedures used to fault isolate an RT to a bad module.
Observe the following when using a flowchart:
a.
Do not start a flowchart unless directed to it by another troubleshooting flowchart or by the operational
check.
b. Do not change RT or test equipment switch settings unless directed to do so by the flowchart or the test
setup diagram.
c.
Refer to chapter 3 for information on the reference fixture and the test adapter.
d. The logic levels in the RT are as follows:
6.75 Vdc logic: logic 0 = -0.7 to 2.0 Vdc, logic 1 = 4.7 to 7.5 Vdc
5.5 Vdc logic: logic 0 = -0.7 to 1.6 Vdc, logic 1 = 3.7 to 6.0 Vdc
negative logic: logic 1 = -5.0 to -7.25 V dc
e.
See figure FO-13 for locations on the RT parent board.
f.
The test responses at some test points are not seen immediately. Check the probe location and
perform the test again to verify a faulty result.
Try rekeying the radio that is transmitting. Test
responses that are difficult to detect will be supplied with presets for the scope.
These appear as:
They give the time base (T), and voltage base (V) suggested settings for the scope.
g.
The reference fixture and REF RT are part of Maintenance Group
h.
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
OA-9297/GRC.
2-47
