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Page 12
SERVICE
Principles of Operation
Troubieshooting
HP 84811A
3.
Connect the Sensor to an 8900C/D Peak Power
Meter.
4.
Apply ፦1.27 volts to the spring contact (see
Figure 3).
5.
Check for approximately 100 milliwatts dis-
played on the 8900C/D. This indicates that
the amplifier circuitry is functional.
If the amplifier circuitry is not functional, use
Figures 4 and 5 to troubleshoot the Sensor. If the
amplifier is functional, the problem is either the
detector diode or the input capacitor.
Refer to the Diode Module Replacement Assembly
instructions to remove diode U1 from the connec-
tor barrel, and to replace the diode. This diode can
be tested using acurve tracer set to5 millivolts and
5 microamps
deflection. The origin resistance
should be about 1 to 2k Ohms in the forward direc-
tion at room temperature.
If the amplifier and the diode are functioning,
replace the RF connector assembly J1. This
assembly, which includes the input capacitor, can
be replaced as follows (refer to Figure 2):
1.
Using a 9/16 inch wrench, remove the RF
connector from the connector barrel. Use a
spanner wrench to hoid the connector barrel
while removing the connector.
2.
Connect the new RF connector to the connec-
tor barrel.
Diode Module Replacement
1.
Disconnect the Peak Power Sensor from the
Peak Power Meter.
2.
Disassemble the Peak Power Sensor by per-
forming the following steps:
a.
Insert the blade of a small screwdriver
between the two piece plastic shell at the rear
of the Peak Power Sensor. Gently pry the two
pleces apart.
b. Proceed to the other side of the connector
and again pry the cover sections apart. Remove
the shells and the magnetic shields (refer to
Figure 5).
c.
Remove the four Allen cap screws.
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