User`s guide

Chapter 3 3-13
Theory of Operation and Troubleshooting
Troubleshooting
1. Press Preset, Meas, Start, 300, k/m, INPUT PORTS, B, TESTPORT 1.
2. If there is a power hole or roll off in the response, check the RF cables.
Refer to Figure 3-14, Figure 3-15, and Figure 3-16 for cable locations.
If no response is seen for channel B, check the bias connection to
switch S2 (see Figure 3-13) and the J5 connection (see Figure 3-17)on
the test set interface board. If the connector is loose, reconnect it. If
the bias connector is firmly in place in the J5 connector, check the
bias voltages on switch S2 (+0.62 Vdc and +16.3 Vdc). The center bias
pin on S2 should be approximately +22 V.
3. Use the tab on the side of one of the switches (S0, S1, S2) as the
ground connection point.
4. The red wire is the common drive pin and should measure
approximately +22 Vdc.
5. The blue wire is the solenoid drive for pin number one. The voltage on
this pin measures approximately +0.62 Vdc.
6. The green wire is the solenoid for pin number two. The voltage on this
pin measures approximately +16.3 Vdc.
7. Measure the solenoid voltages.
NOTE Voltages may vary depending on the test port state of the instrument.
a. Press Seq, TTL I/O, TTL OUT, TESTSET I/O FWD, 5, x1, I/O FWD, 7, x1.
b. Toggle between 5, x1 and 7, x1 while measuring bias pins 1 and 2
on S2.
The voltage on bias pins 1 and 2 should alternate between
+0.62 Vdc and +16.3 Vdc when the instrument is toggled from 5, x1
to 7, x1. If the bias voltage changes state but there is still no RF at
Port 1, the transfer switch S2 (see Figure 3-13) may need to be
replaced. If the bias voltage remains the same, check the LEDs to
make sure the source test port is being redirected.