Codan NGT 2010 RF Technical & Service Manual page 676

NRI—Fault finding
Table 9: Test points on the NRI Vocoder PCB
Test point Description
+10 V Regulated +10 V
supply rail from NRI
Microcontroller PCB
TP17 Charge-pump
generated negative
supply rail
–5 V Regulated –5 V rail
generated from above
TP7 Internally multiplied
clock signal
TP13 SRAM Read Signal
TP14 SRAM Write Signal
TP15 SRAM Chip Select
Signal
TP3 Codec Clock Signal
282
Acceptable
signal/level
+10.0 V ±0.1 V
–7.0 V ±0.5 V
–5.0 V ±0.1 V
40 MHz ±500 Hz
5 V p–p square wave
Normally logic high
with fast low pulses
Normally logic high
with fast low pulses
Normally logic high
with fast low pulses
2 MHz ±100 Hz
5 V p–p square wave
Possible fault causes Action
Failed connection
Failed +10 V supply
on NRI
Microcontroller PCB
Failed charge-pump
component
Failed –5 V regulator Replace PCB
Failed CoDec
Failed voltage
regulator
Failed CoDec
Failed connection
Failed CT8020
Failed CT8020
Failed RAM IC
Failed CT8020
Failed RAM IC
Failed CT8020
Failed RAM IC
Failed CT8020
Failed Codec
NGT Transceiver System Technical Service Manual
Check condition of
J1, and P206 on
NRI
Microcontroller
PCB
See Table 8
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Check condition of
J1, and P206 on
NRI
Microcontroller
PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB
Replace PCB