Bruce BR3000-330-2CL - Test Scenario Execution: LCM LED Check; Data Cable Testing

BR3000-330-2CL,-3CL,-2EN CMM and IPL
Document No. 33-21-57, Rev. A
Page 41
5.6.3 Test Scenario Execution: LCM LED Check
1. With the aircraft on the ground, execute the Test Scenario as described in
Section 4.1.5. Verify that all LCM units respond by transitioning through the four
primary colors (R, G, B, W) in a continuous loop.
a. If a single LCM unit fails to respond to the Test Scenario, replace the
affected LCM unit.
2. With the Test Scenario executing, check each LCM unit to ascertain that there
are no faulty LED emitters. Wait for all LCM units to cycle through the four
primary colors (R,G,B,W).
a. If an LCM unit has one or more faulty LED emitters, replace the affected
LCM unit.
5.6.4 Data Cable Testing
If a data cable issue is suspected with the BR3000 MLS, use the following procedures
to isolate the fault to a single data cable assembly or connector.
5.6.4.1 Issue #1: All LCM Units on a Ceiling or Sidewall Data Trunk Fail to Respond
During the execution of the Test Scenario, if all of the LCM units on either the Ceiling
bus or Sidewall bus for a particular MLCP zone fail to respond to the Test Scenario, this
can indicate the following conditions:
 A short on the affected Sidewall or Ceiling trunk.
 Faulty MLCP unit
 Open CAN data cable between the MLCP unit and the first LCM unit in the
affected Sidewall or Ceiling trunk.
To diagnose this fault, first check for a shorting condition on the data trunk as follows:
1. Remove the MLCP unit exposing the 37-pin D-shell connector behind the unit.
2. If the problem is on the Sidewall data trunk, use an ohmmeter to measure the
resistance between pins 6 and 24 on the MLCP connector.
a. Resistance reading less than 10 ohms: Shorted data cable on trunk.
b. Resistance reading of 100 to 150 ohms: Normal
c. Resistance reading greater than 1000 ohms: Open data cable on trunk.
3. If the problem is on the Ceiling data trunk, repeat the above procedure,
measuring between MLCP connector pins 5 and 23.
4. If a shorting condition on the affected CAN trunk is not identified, it is likely that
the problem is with the MLCP unit itself.