User`s guide

3-14 Chapter3
Theory of Operation and Troubleshooting
Troubleshooting
When the instrument is toggled from Port 1 to Port 3 and from
Port 1 to Port 2, the bright LED should remain on Port 1. If the
LEDs are working on Port 1 to Port 3 and Port 1 to Port 2, and the
bias voltage is still incorrect on switch S2, remove the J5 bias
connector (see Figure 3-17) from the test set interface board and
move the S4 bias connector from J14 to J5 on the test set interface
board. Check the bias voltage on S4 and toggle between the
TESTSET I/O FWD, 5, x1 and TESTSET I/O FWD, 7, x1 states. If the
bias voltage does not change, replace the test set interface board.
If the bias voltage does change, replace S2.
If the B channel response is degraded or a bad load match exists
on Port 3, this may indicate a bad test port coupler. To check the
load match on Port 3, follow the instructions on the verification
procedure in this service guide.
Figure 3-4 Roll Off