NRI—Fault finding
NGT Transceiver System Technical Service Manual 281
Testing the NRI Vocoder PCB
The NRI Vocoder PCB features a highly integrated dedicated voice coding DSP
(CT8020). Consequently it is difficult to diagnose faults with this PCB without the use of
specialised test equipment. The following tests establish basic functionality of the
Vocoder.
AUD+ CIB system
audio +
+5 V with ∼ 6 µs wide
5 V p–p high-going
pulses every 80 µs
Failed programmable
logic device
Replace PCB
Failed analog
component(s)
Replace PCB
Firmware failure Attempt to
reprogram if
possible
NOTE
For AUD– and AUD+, the NRI must be in Master Bus mode to make
these measurements. This mode requires a standard type NGT Junction
Box 2030 connected to the NRI via cable 08-05610-00X. The junction
box must be connected when the power is off.
Drawing 08-05870
Table 8: Test points on the NRI Microcontroller PCB (cont.)
Test point Description Acceptable
signal/level
Possible fault causes Action
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