Got a 401 crashing intermittently while running, both directions, anywhere in the shaft, doors in or out of service. Only thing logged is ddrive, always resets, recovers, and re-initialises. No drive fault LEDs. Have swapped out: Elevator control board, 12 SCR board, voltage divider board, gate firing pcb, new SCR rack, new current sensors, new main processor, new A1 unit, relay I/o, power amp board, transducer I/0, checked all locks and car gates, swapped brake/motor power amp, changed dfo dfc relays, new cop1 board, governor masking contacts, lock cover circuit, auxillary gs. This bastard of a unit still crashes intermittently. Any suggestions? Desperate.

what do you mean by crashing? does it just drop the brake and stop or does it run through floors? check your motor field contact for pits on the little contact. have you swapped pvt's?

what about 1 and 2M auxilaries or armature plates with cracked strikers

or are you sure its the drive, as greenpants says CHANGE the PVT and also check the PPT....and are the couplings on them tight

Greenpants, it is crashing as in dropping the brake about 3-5 seconds into a run. Usually it recovers and continues on, sometimes will repeat the fault about 4 times before it recovers. It never shutsdown completely.

Have had a look at the ppt, all seems fine. Have swapped 1m and 2m auxillaries and microswitches, both 1m and 2m are making together and all contacts have been cleaned. Motor field contact has been cleaned and making well with decent wipe.

I have not swapped th PVT thats a good idea that may well be my next course of action.

Thanks greenpants and kiwi for your input will let you know how i go.

Hey guys. Well, the pvt was changed and it ran like a dream.... for about 12 hours. Then the same fault reared it's ugly head once again. I'm just about completely lost although one of the only things i have not done is test the motor. its a 131ht gearless machine. Anyone know of common issues maybe with these motors?

which direct drive do you have? anything showing up on a 40 test? have you changed brake switches? 131ht's have those long micro switches that can get hung up. you can upgrade to a new style box and switch if you feel the need. check pvt wiring for damage. any time/heat correlation when it fails? im assuming you work for otis call a RFE.

The dd is Louis Allen. Tried to simulate the fault by o/c the brake switches while running, does not produce the fault. PVT wiring is good no problems all bells out ok. No apparent heat/time issues either.

If this is Louis Allis then you must be using a tach motor rather than an encoder for the speed feedback. Check your dc tach for AC ripple. You can use a scope but an old Simpson or Triplett with an output lead connection works just fine. Verify you don't have a carbon problem in the tach particularly if the brushes are oriented at 12:00 and 6:00. Also check all the ribbon cables in the drive for proper connection. Louis Allis drives have poor clips on some of the connections and this causes problems if the drive swing panel is open and closed. How is the drive tracking? Louis Allen drives typically needs more lag than most newer drives. You will need a scope for this part. Using a scope set one channel to observe your speed reference and the other channel to observe speed feedback. Put the signals on top of each other and see how well the tach follows the pattern. Have you checked your loop circuit for grounds? Improper current feedback will cause trips as well, thus the need to make sure your loop is clean. Most drive problems come down to problems with your feedback loops. How does your brake look? Check for signs of bluing or glazing on the brake drum. An intermittently dragging brake can cause plenty of problems.

I know you said in your first post that you checked the locks and gate, but what are they doing at the time of failure? I've seen a situation where the safety circuit or door locks open in flight, and the drive develops a sympathetic fault. Because after the pattern ceases, the motor doesnt stop instantaneously, so the tach feeds into the drive for a split second, and that generates a drive fault. I'd hang light bulbs on key circuits, safe, doors, gate, pattern, unless you got a quad trace scope. For some reason, the sequence of lights going dark sticks in my mind, even when i'm not looking directly at them. Yes, I've got a dual trace scope, but lights serve wonderfully, for high-low status indicators. The Wurtec S3 logic analyzer has high impedance inputs that can be fooled by noise, so I'm not too fond of it, but that's another way to go sometimes.

The key is to never lose sight of the fact that in the end it's an elevator. Over the years I've been doing this I seen guys get hung up on noise related stuff only to find out later that there was a loose wire. Always go back to basic elevator first. Things such as loose controller wires, interlocks and gate switches, door limits and safety circuits. Often you will find ten other potential problems before you find the one that shuts the unit down. If we are looking at noise suppression issues remember that MOVs break down over time and should be replaced. Here again a scope comes in handy when you can monitor low voltage power supplies such as 5 +-12 or 15 volts for noise spikes. Poorly suppressed relays will often leave nice glitches on your power supply rails. If you can find a pattern in the shutdowns you are about halfway there. What about a comp rope or chain that occasionally is bumping a buffer switch in the pit? Does the problem disappear if the car is on door disconnect? Installing a video camera to monitor the status led's for a couple of days is another option. Another thing is to verify things with your own eyes.

Had one that would fail and produce a drive fault on a long run of more than 10 floors. And yes lights work great! Found the hoistway air from the elevator moving would flutter the pit door.

Nice one, Mr Sands! Fluttering pit door!

I hope your not being a bit unbelieving there Vic
It does happen not just the pit door but normal door lock/high resistance safety circuit etc..take it from me it can take days to track that down. Im not a 401 expert by any means just someone that has LOT of breakdown experience on them.

I absolutely beleive what he said.
I was just answering like I talk, spontaneously. (Vernacular typing?) It was meant to be like- "Oh, wow, cool find, dude!" If we could hear the inflection in each other's voices, you would know right away. Printed text takes away about half of our communication abilities.

yeah I know how it is , wish there was some way of actually saying it how you say it, and not just by smilies or emoticons without going into thousands of words!!!

8^)