Troubleshooting
6-74 Manual # 42-02-1P21
Using the MLT / VLT Data Trap
The MLT / VLT “data trap” records many of the controller's operation “flags” at the moment the
MLT or VLT occurs. This allows you to see what flags led up to the fault. Note: Direction must
be on (input UPS) for the adjustable time set via parameter MOTOR LIMIT TIMER (1 - 6 min-
utes) before MLT will occur. Direction must be on (input DNS) for the adjustable time set via
parameter VALVE LIMIT TIMER (1 - 6 minutes) before VLT will occur.
Once an MLT or VLT shuts down the car, use these steps to look at the stored flags.
1. Do not reset the computer as this will clear the data trap on software version 5.19.0001
or earlier. To return the car to service and not harm the data, simply toggle the relay
panel inspection switch from OFF to ON and back to OFF.
The data is not cleared on power up or reset. The data is overwritten each time a new MLT
occurs. However, the data may be cleared and the MLT counter reset by placing the F1, F2, F7
and F8 switches in the up position.
2. On the HC-MPU board place the F2 switch up (ON) to select External Memory. All other
switches should be down (OFF). The LCD display shows the default address, DA.0100
(address 100 Hex) followed by the eight memory bits at that location.
3. Use the DATA TRAP MEMORY CHART to determine the addresses where the saved
data is stored. The section in the Controller Installation Manual titled EXTERNAL
MEMORY MODE provides a complete description of how to use the External Memory
Mode. Briefly, use the N push button to select the digit to be changed (digit blinks on
and off). Press + or - to change the digit.
4. Record the data displayed on the LCD for all rows shown on the chart. It helps if you
have a few photocopies of the chart. Simply mark the positions in the chart that are
shown as a “1” on the LCD display. Addresses 0480 through 0493 contain car status
flags. Address 0494 contains the car's position indicator value at the instant the MLT or
VLT condition occurred and address 0495 contains the MLT counter. Only the labeled
positions are important to mark.
5. Use the recorded values and the timer logic flowcharts to help determine the cause of
the problem. Then call MCE for assistance if any is needed.
* Note: To determine the software version, place switch F8 up (ON) with all other function
switches down (OFF).
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