6881096C74-B May 25, 2005
Troubleshooting Procedures: Receiver Front-End (RXFE) 4-33
4.11 Receiver Front-End (RXFE)
This section provides band-specific troubleshooting procedures for the receiver front-end.
4.11.1 VHF (136–174 MHz) Band
Use this information, along with the theory of operation, to diagnose and isolate the cause of failures.
The principle tools needed to troubleshoot a circuit to the component level are the schematic and the
theory of operation.
In addition to the schematic and theory, you can use the troubleshooting flowcharts in "Chapter 5.
Troubleshooting Charts" that will guide you through a sequence of tests and checks designed to
isolate problems.
Prior to troubleshooting, it is important to review the theory of operation including specific
precautions and troubleshooting methods. Because much of the radio’s circuitry operates at a high
frequency, measurements must be taken carefully.
4.11.2 UHF Range 1 (380–470 MHz) Band
Use this information, along with the theory of operation, to diagnose and isolate the cause of failures.
The principle tools needed to troubleshoot a circuit to the component level are the schematic and the
theory of operation.
In addition to the schematic and theory, you can use the troubleshooting flowcharts in "Chapter 5.
Troubleshooting Charts" that will guide you through a sequence of tests and checks designed to
isolate problems.
Prior to troubleshooting, it is important to review the theory of operation including specific
precautions and troubleshooting methods. Because much of the radio’s circuitry operates at
400 MHz, measurements must be taken carefully.
Table 4-21. Standard Operating Bias: VIP Lines (W3 Remote Configuration)
Nominal Value Signal Name Range/State Probe Locations
VIP_OUT_1_5v Access only by custom
pin-out
J0401-13
VIP_OUT_2_5v Access only by custom
pin-out
J0401-14
NA VIP_IN_1_5v Not supported with W3 J0401-15
NA VIP_IN_2_5v Not supported with W3 J0401-16
SW_B+ level VIP_OUT_1_12v Deactivate = relay
closed
J0401-11, J2-18
0.3 V to 0.5 V Activate = relay open
SW_B+ level VIP_OUT_2_12v Deactivate = relay
closed
J0401-12, J2-19
0.3 V to 0.5 V Activate = relay open
Note: When using the W3 control head and interconnect board, the main board VIP_OUT lines are
pass-through-only lines.
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