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DMC has me scratching my head

Posted By: ashley

DMC has me scratching my head - 01/24/20 05:31 PM

So trying to figure out a DMC issue. Summary of problem with elevator:

Elevator operates normal in down direction. However, in up direction elevator takes call, starter starts up briefly (less then 2 seconds) then cancels call. Immediately after one can place a call and it will respond normally, however then next time an up call is placed, it will take call, starter starts up briefly (less then 2 seconds) then cancels call, followed by a normal run.

The car was originally blowing F2 and F3 fuses. This problem was traced to the selector main board, received replacement board form World and the car would no longer low fuses, however it would not learn the hoistway and operate on normal operation. It would always get a “DZR NOT True when expected” fault. We then sent in the board to be tested, it tested out good, we therefore replaced the sensor board with a replacement from World. Once installed the car would learn the hoistway however the problem above occurs consistently. When it occurs the Freedom tool shows loss of communication on all three boards at the time the elevator drops out. We tested the capacitor and it meters out OK. When testing the 24V on P24C it doesn’t drop out, at least not detectable by a digital voltmeter. It doesn’t even flicker. The power supply is providing 5VDC and 12VDC and is also not dropping (tested by digital meter) during the loss of communication. We therefore believe the problem is either in the CLC board or the power relay board. Being as it happens just in the up direction, we are leaning towards the power relay board being the issue, but the board has no impact on the communication, other then the suppling voltage to the CAR, which powers the CLC, and we are not detecting a loss of power, however the errors occurring during the failed run are:

Selector: “Run Command Fault”
Door Operator: No Faults
CLC: “Actual Power Loss to System not detected”

We pulled the relay board and the CLC and sent to world to have inspected and repaired, but I hate being a parts changer. Does anyone have another clue?
Posted By: john jay

Re: DMC has me scratching my head - 01/24/20 06:32 PM

Digital meters are too slow to catch a quick power glitch. Try a Triplett or a Simpson analog meter. When the contactor pulls in, you may be bouncing something.
Posted By: ashley

Re: DMC has me scratching my head - 02/03/20 09:40 PM

Just an update, WE tested the power relay board and it checked out, the CLC had some bad communication chips. Running well now.
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