Codan NGT 2010 RF Technical & Service Manual page 675

Table 8: Test points on the NRI Microcontroller PCB (cont.)
Test point Description
AUD+ CIB system
audio +
NOTE
Testing the NRI Vocoder PCB
Drawing
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.
NGT Transceiver System Technical Service Manual
Acceptable
signal/level
+5 V with ∼ 6 µs wide
5 V p–p high-going
pulses every 80 µs
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.
08-05870
Possible fault causes Action
Failed programmable
logic device
Failed analog
component(s)
Firmware failure
NRI—Fault finding
Replace PCB
Replace PCB
Attempt to
reprogram if
possible
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