User`s guide

Chapter 3 3-9
Theory of Operation and Troubleshooting
Troubleshooting
Symptom 2: No RF Source at Port 1
Check the bias connection to the switch S0 (see Figure 3-13) and the J3
connections (see Figure 3-17) on the test set interface board. If the bias
connector is loose, reconnect it. If the bias connector is firmly in place in
the J3 connector, check the bias voltages on the switch S0 (+0.62 Vdc and
+16.3 Vdc). The center bias pin on S0 should be approximately 22 V.
1. Use the tab on the side of one of the switches (S0, S1, S2) as the
ground connection point.
2. The red wire is the common drive pin and should measure
approximately +22 V.
3. The blue wire is the solenoid drive for pin number one. The voltage on
this pin measures approximately +0.62 V.
4. The green wire is the solenoid drive for pin number two. The voltage
on this pin measures approximately +16.3 V.
5. Measure the solenoid voltages using the following procedure.
NOTE Voltages may vary depending on the test port state of the instrument.
a. Press Preset, Meas.
b. Toggle between REFL: FWD S11 (A/R) and REFL: REV S22 (B/R) while
measuring bias pins 1 and 2 on S0. The bias voltage on bias pins 1
and 2 shouldalternate between +0.62Vdc and +16.3 Vdc when the
instrument is toggled from REFL: FWD S11 (A/R) and
REFL: REV S22 (B/R). If the bias voltage changes state but there is
still no RF at Port 1, the transfer switch S0 may need to be
replaced.
Before replacing switch S0, check the receiver section for Port 1 to
make sure the test port coupler is functioning correctly. If the bias
voltage remains the same, check the LEDs to make sure the
source test port is being redirected. When the instrument is
toggled from REFL: FWD S11 (A/R) to REFL: REV S22 (B/R), the bright
LED indicates the incident port and the dim LED indicates the
receiver port.