Fault 7 t-4

We have a group of 3 that one car faults out with Number 7 negative target distance and indeed the car is 1/8 inch below or above the floor. We have learned the shaft, relearned the shaft, replaced the gov. encoder, the motor encoder, checked and replaced the wiring from each encoder back to the controller. We get this intermittent shut down, with no rhyme or reason. Sometimes it will go 60 days with out shutting down, and then it happens every other day.

Have you looked at the governor rope some times they get build up on the rope or in the sheaves. Also might check the encoder couplings make sure they aren’t slipping on the shaft. Make sure your governor hitch point is tight

If you have the typical optical governor encoder make sure the plastic is clean and sensor depth is correct. Have you tried a DSP?

Thats a good point Boomer. Will double check all of that. IDWT, yes all three have the very simple optical encoders. Did not check sensor depth, but will. You mean replace the DSP board?

Ya, position encoder goes into the DSP through optocouplers on the board and is where the current position is stored.

UPDATE

Just went down for the first time since the 8th of June. I was hoping we had it, as we checked over the points that Boomer and IDWT had.

We will now replace the DSP card and see what happens.

If you eliminate other options, check PMI inputs that are high speed precise switching LU , LD , DZ, etc. Keep in mind position count updates/ corrects when passing through leveling vanes. MAKE SURE THEY ARE NOT CRYDOM. If they are Gordos or Grayhill they are probably fine. The CRYDOM PMI modules are slow switching and could cause leveling, position, ntsd, etsd errors.

His parameters are changing back to default.. probably bad EEPROM!

Problem has never gone away and we have been trying different things to get to the bottom of it. Still no luck. Group of three, car three is the one that we have had the issues with and no rhyme or reason of shutting down with fault 7. However, if car 2 has power shut off, car three does not fault out. Car two starting faulting out with 7 and we were looking at that car while waiting for parts we noticed that car 3 does not fault out. We have had car 2 shut down for over 45 days and no issues. Turned it on and three days later car 3 faults with 7. Changed power supplies on all three, dsp cards, encoders, gov optical readers, encoder wiring, check terminals, connectors etc. Since COVID we can afford to have one car shut down, but soon that will not be the case.

Looking for ideas?

have you turned number on, but not let it run, (on inspection or Ind Svc.) ? I had one that when car 2 of 6 ran, it would trash all NP and IN modules on the other cars. Turned out to be a wire pulled across the brake resistor had melted and was introducing high voltage into the low voltage circuit. This happened during construction, so it was easy to find. But when you say that if number 2 is off, it doesnt fault, we dont know if it is because it doesnt run, or because the power is off. Inspection stops running, so does Ind Svc as long as CD is disabled. This allows more of the circuit in play.

Yes power is off, but we will try it with car 2 on inspect and power on.

Have you scoped encoder lines for noise on all cars? Do encoders share conduits?

We have not scoped the lines but did replace them. They do not run in shared conduits and we have the encoder wires alone in conduit.

Update after Johnny's post.....
01/27/2021 We turned the power on to number 2 but left CPU card off and on inspect. Car 3 did not fault out at all.

02/03/2021 turned CPU card on for car number 2 and left on inspect. Car 3 faulted out 02/08/2021 with Fault 7.

Thinking out loud, but that seems to eliminate encoder noise, as car 2 was not moving at all.

That is strange... you need to put a scope on car 3’s encoder channels and see if there is any noticeable noise with car 2 on vs off. If there is, even if not enough to fault it while you’re watching, you can try removing things on car 2 to see if it goes away like picked relays, drive power to bus, other boards in card rack, etc.

Thanks, and will keep it posted.