Section 4 Auto-Zone Plus
4-10 Start-Up and Troubleshooting
1.3.3 Checking the CommLink II Driver
Diagram
Overvie
This test checks for proper Network loop voltages coming from the CommLink II.
Tip: The Loop LED (located on the front panel) should “flicker” when the CommLink II is
attempting to communicate. The Loop LED will flicker more noticeably for a few
seconds when first powered up. If the LED does not flicker, the unit is not functioning.
Proper loop voltages are essential for reliable communications. It is normal to see
fluctuations at this point on the CommLink II. The average value should be close to the
acceptable range described below. Values will vary upon initial powerup for about 10-15
seconds as the unit attempts to communicate.
Measurements
Local Loop Acceptable Range
T - G (SHLD) 2.4 - 2.5 Volts DC
R - G (SHLD) 2.5 - 2.7 Volts DC
Action
Condition Action
If voltages are too high or too low on either
side
1. The CommLink II has a damaged comm
driver chip. Replace the driver chip.
See "1.3.11Comm Driver Chip
Replacement”.
2. The CommLink II is defective.
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