Nautel NX50, Руководство по устранению неисправностей

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NX50 Troubleshooting Manual Responding to alarms
Issue 6.0 2019-04-01 Page 1-57
5. If the measurements in Step 3 and Step 4 are satisfactory, but the RF power module
continues to display alarms when installed in the transmitter, replace the RF power
module.
Resistance measurements
Complete the following resistance measurements for each suspect RF power module.
See Figure 1.7 on page 1-59 to identify the power MOSFETs on the RF power module.
1. Remove fuse F1 from its holder and measure its resistance using a digital multimeter. A
blown fuse will measure an open circuit. If the fuse is OK, return it to its holder.
2. For each power amplifier MOSFET (Q7 through Q10) and each modulator MOSFET
(Q11, Q12 and Q13), use a digital multimeter to make the following resistance
measurements. Note that Q7 through Q10 have screw-head terminals and Q11
through Q13 have solder pads (see Figure 1.7 on page 1-59 ):
• Check for 1,000

between the gate and source.
• Check for an open circuit between the gate and drain.
3. If either measurement in Step 2 is not satisfactory, replace the affected power amplifier
MOSFET (see “Power Amplifier FET replacement” ) or modulator MOSFET (see
“Modulator FET or Free-Wheel Diode replacement” on page 1-62 ), as applicable, or
replace the RF power module.
Protection Diode checks
Complete the following protection diode checks for each suspect RF power module.
See Figure 1.7 on page 1-59 to identify the protection diode on the RF power module.
1. Use a digital multimeter (on its diode setting) to check protection diode CR9, noting
the anode (A) and cathode (K) markings (see Figure 1.7 on page 1-59 ):
• Check for a voltage of between 0.5 and 0.8 V with multimeter test leads in the
forward bias orientation (+ on anode, - on cathode).
• Check for an open circuit with multimeter test leads in the reverse bias orientation
(- on anode, + on cathode).