User`s guide

3-24 Chapter3
Theory of Operation and Troubleshooting
Troubleshooting
4. The green wire is the solenoid for pin number two. The voltage on this
pin measures approximately +16.3 Vdc.
5. Now 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, 6, x1, I/O FWD, 5, x1.
b. Toggle between 6, x1 and 5, x1 while measuring bias pins 1 and 2
on S4.
The voltage on bias pins 1 and 2 should alternate between
+0.62 Vdc and +16.3 Vdc when the instrument is toggled between
6, x1 and 5, x1. If the bias voltage changes state but there is still no
RF at Port 1, the transfer switch S4 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.
When the instrument is toggled from Port 1 to Port 2 and Port 2 to
Port 3, the bright LED will change from Port 1 to Port 2. If the
LEDs are working on Port 1 to Port 2 and Port 2 to Port 3, and the
bias voltage is still incorrect on switch S4, disconnect the J14
connector (see Figure 3-17) and check the bias voltage on S3 (see
Figure 3-13). Toggle the instrument between TESTSET I/O FWD, 6,
x1
and TESTSET I/O FWD, 5, x1. If the bias voltage changes, replace
S4. If the bias voltage does not change, replace the test set
interface board.
If the B channel response is degraded and a bad load match exists
on Port 2, this may indicate a bad test port coupler. To check the
load match on Port 2, follow the verification procedure instructions
in this service guide. Replace the Port 1 coupler if the Port 1 load
match fails.