Virginia Controls, LLC
MH-3000 User Manual, 1_03C10-VC
Page 103
9.
Troubleshooting Suggestions
Troubleshooting is similar to any other controller, and has several features to speed up
determining the cause of any problem. No special knowledge of the operation of the
microprocessor is required to be able to troubleshoot it.
A safety relay interface is provided to prevent dangerous operation due to a failure of the
microprocessor. It is possible that the microprocessor may turn on an output point, yet the
field safety switches may prevent the associated device from energizing.
For example, if the up run output energizes, but the up normal switch is open, then the
up run valve(s) will not energize.
9.1
Locating Faults
Once the system has been installed, and is running properly, the most common problem
will be the failure of an external device. The first step in locating the cause is to determine
whether the fault is in the microprocessor or whether it is in the external wiring.
For example, if a position indicator light is not lit, check the output module for the
appropriate output point to determine if the microprocessor is trying to turn the light on or
not. If the output light is on, then confirm that there is voltage at the module terminal. If
there is voltage at the module terminal, then the problem is external to the microprocessor.
It could be in the wiring to the position indicator, or perhaps the position indicator light has
burned out. Similarly with input points, check that the input module light is on, that there
is power at the terminal, and if not then the problem is external.
If it is determined that the problem is with the microprocessor, then the next step is to
determine if the problem is in the hardware or the software. Using the keypad, press Nxt
to display the "Show I/O Status" menu item. Press Ent. The screen will show the address
on the top line and the I/O status on the bottom line. Press Nxt or Prv to show the desired
I/O address, and see if the CPU is responding by showing the correct status of the I/O
points. If it is not, then the fault is probably with the I/O hardware; if it is on, then the fault
is probably with the software.
If an input or output board fails, it may be possible to temporarily replace that defective
board with another board that is used for non-essential functions (such as call register
lights), thus providing elevator service while a replacement board is being obtained. See
the section on I/O Board Replacement for further information.
If this does not correct the problem, the power supply or the CPU module could be faulty.
If the CPU fails, it will probably stop flashing LED D5. The CPU and I/O modules can be
affected by high transient surges in the power supply, such as the building being hit by
lightning. This may damage the CPU, or alter the contents of the program. Proper
grounding will protect the controller from most of these problems.
