MXD5U OPERATIONS AND MAINTENANCE
•
Before ap28V to the module, adjust R12 fully clockwise. Limit the power supply current to 3.0A.
•
Apply +28V to the B+ terminal. Monitor the current and adjust R12 counter clockwise (CCW) for a total
current of about
1.0A + 0.05A
.
•
Proceed to the next step if a network analyzer or similar equipment is available.
•
RF SWEEP: Adjust C7 for best frequency response. With the bias set at 1.0A, the gain in the range of
470MHz to 860 MHz should be 15 to 16dB.
4.2
4.2.1
4.2.2
4.2.3
B
ASIC
T
ROUBLESHOOTING
T
ECHNIQUES
As mentioned earlier, one of the best tools in troubleshooting is knowing what the nominal figures or typical
values of the amplifier when it is at its normal performance. If a fault condition occurs, then you can compare the
data taken previously with the present conditions and come up with a reasonable conclusion about what is at
fault.
The following describes some fault conditions and possible solutions.
Amplifier
Completely
OFF
The amplifier is equipped with a fused AC line filter. Although it rarely happens, abnormal conditions such as
power surges may cause the fuse to blow. Blown AC fuses will completely shutdown the amplifier. In this case,
replacing the fuse will rectify the problem.
No RF Output
•
Check for proper power supply voltage.
•
Check for potential connector problems causing either no drive to a module pallet (input connector) or VSWR
(output connector) problems.
Output Reduced to 25%
If the output is approximately 25%, a possible cause is a failure of one of the devices in the IPA. This stage has
dual devices so that if one fails the output of that stage will be reduced to quarter power (25%). A measurement of
the current drawn by the amplifier will determine if this condition exists. The IPA usually draws 1.0A. If the current
is 0.5A, then this is the case.
PUB09-03 Rev 0 April 16, 2009
09-03-12
MXD5U Operations and Maintenance
