Nautel NX50, Troubleshooting Manual

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NX50 Troubleshooting Manual Responding to alarms
Issue 6.0 2019-04-01 Page 1-81
Low Voltage Power Supply Replacement
See Figure 1.19 .
1. Set the transmitter to its RF Off state and turn off (disable) the ac power at the source.
Lift the air filter (slide it up) to verify the LEDs on the power module interface PWBs
are off (green when on), indicating the B+ capacitors are discharged. Open the rear
door of the cabinet and verify the three ac indicator LEDs on the rectifier assembly are
off (amber when on). For additional safety, measure the dc voltage across the + and -
terminals of any of the large, electrolytic capacitors on the floor of the cabinet as well
as the line-to-line and line-to-ground voltages at the ac input terminals. There should be
little or no ac or dc voltage. DO NOT PROCEED if either the ac or dc voltage is
greater than 5V.
2. Disconnect all wiring attached to the affected power supply module (U3 through U7),
taking note of the connector labels on the cables.
WARNING:
Lethal voltages exist inside the transmitter when the power is turned
on. Turn off (disable) and lock out the power at the source and verify
no dangerous ac or dc voltages are present before removing any
connections or PWBs.