Auto-Zone Control Systems Auto-Zone CV & CV-EX Systems Installation & Operation (Version 01C) - Manual (Page 107)

Auto-Zone CV & CV-EX
Section 4
Start-Up and Troubleshooting 4-29
Checking the Local Loop at the MiniLink – CV-EX
Diagram
Meter Set To Read DC Volts
+ -
+
-
+2.4 VDC
to
+3.3 VDC
R - to - G T - to - G
+ -
+
- +2.4 VDC
to
+3.3 VDC
To Other MiniLinks
Or CommLink
On The Network Loop
To Other MiniLinks
Or CommLink
On The Network Loop
MiniLink
MiniLink
To CV Controllers
And System Manager
On Local Loop
To CV Controllers
And System Manager
On Local Loop
The indicated values are typical of a normal system. Actual readings may deviate slightly
due to the number of units connected and other system-specific factors
Note: These tests assume that the MiniLink being checked is powered up.
Overview
This is a “quick check” to determine if any of the CV Units on a Local Communications
Loop are damaged. Since all CV Units will “float” their communications connections at
about 2.45 Volts, you can quickly check an entire loop by unplugging it at the MiniLink.
Note: Be sure that the loop you are testing does not have a short circuit from T - R.
Damage typically occurs when the communications loop is exposed to excessive voltage as
may occur during installation due to wiring errors. The driver chips are socketed on all
boards to facilitate servicing. It is unusual for driver chips to fail during normal operation.
Almost all failures occur due to wiring-related problems.
Measurements
Local Loop Acceptable Range
T - SHLD 2.4 - 3.3 Volts DC
R - SHLD 2.4 - 3.3 Volts DC
Action
Condition Action
If voltages are too high or
to low on either side. 1. One or more of the attached controllers has a damaged
Comm Driver chip. Replace the driver chip. See
Figure 4-10 & 4-11.
2. Wiring errors such as "crossed connections", short
circuits, etc.