8571—Fault finding
NGT Transceiver System Technical Service Manual 353
Fault finding
Finding faults within the split-site remote control system requires the full system to be
connected together.
The types of faults that can occur are:
• no reception, with or without signalling
• no transmission, with signalling
• no signalling
Voltage measurements
The circuit diagrams and the relevant circuit notes give voltages at various points under
various conditions and are useful for locating the faulty section of the remote control
equipment.
The parameters listed below should always be checked first.
Drawing 08-05995
Table 7: Supply voltages for the Backplane PCB
Supply Description Voltage Source
A rail Unregulated DC supply 14 V nominal external transceiver in
12 V systems
+5 rail +5 V regulated supply 5 V ±0.4 V IC1
Drawing 08-03993
Table 8: Supply voltages for the Microprocessor & TCVR Interface PCB
Supply Description Voltage Source
B rail +10 V regulated supply 10 V ±0.2 V IC10
+5 V +5 V bias supply 5 V ±0.5 V junction R44/R45
2.5 V +2.5 V bias supply 2.5 V ±0.25 V junction R34/R35
5 V ref +5 V reference for ADCs 5 V ±0.2 V V5/R42
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