Nautel VX150, Troubleshooting Manual, Page: 43 / 182

VX150 TO VX2 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
VERSION 2.0 2023-04-20 PAGE 3.1.35
PA Resistance Checks
Repeat for PA2 (for VX1.5/VX2 only, if applicable).
1. Using a digital multimeter, check the continuity across fuse F1 on the suspect PA PWB.
 If the measurement is an open circuit, replace the PA PWB (see Power Amplifier PWB
Replacement, on page 3.1.60 ).
 If the measurement is short circuit (near 0

), proceed to Step 2 .
2. Using a digital multimeter, measure the resistance between each gate lead of the FET and the
metal flange of the FET. Note: gate leads are located on the same side of the FET as the input RF
connector.
 If the measurement is less than 8 k

, replace the PA PWB (see Power Amplifier PWB
Replacement, on page 3.1.60 ).
 If the measurement is between 8 k

and 17.5 k

, check the other PA PWBs for a failure. If
none of the other PA PWBs have failed, replace the original suspect PA PWB.
 If the measurement is greater than 17.5 k

, proceed to Step 3 .
3. Disconnect the PA Volts cable from E1and using a digital multimeter, check the continuity between
each drain lead of the FET (positive meter probe) and the metal flange of the FET (negative meter
probe).
 If the measurement is open circuit, the PA PWB is OK and does not require replacement.
Continue troubleshooting and suspect a problem with an associated PWB.
 If the measurement is not open circuit, replace the PA PWB (see Power Amplifier PWB
Replacement, on page 3.1.60 ).
CAUTION! Perform the following checks with the Ac power disconnected from the
transmitter. FETs are static sensitive and must be handled in a static protected
manner.