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Reply to "PS3 E44 Arc and Fail"

Hi G:

My apologies if I have been unclear on some of this.

  1. When I get a locomotive, anything and everything to do with rollers comes out.  All except the block in the middle/rear of the truck where the red roller wire and black return wire are fastened together, but the red roller wire has been removed.
  2. Out of the box, the PS3 board is fed by the red 'hot' wire that comes from a pantograph/roller selector switch.  I pull that switch out and feed the board directly via the red 'hot' wire from the pantograph.
  3. The truck and frame are (or should be) the same potential, and constitute the circuit return via the black wire off the board that is fasted to both trucks, and thus the outer rails.

Every MTH locomotive I have ever owned has been so configured, and I have never had a problem in over 4 years over catenary operations.  It seems to me a very simple concept, done just like real electric locomotives.

Last week there was significant arcing between the frame and the forward truck, indicating one of 2 faults:

  1. The frame and truck are at different potentials, by a 'hot' frame or something else.  After many hours of working with the unit, I can come up with no possible way how that condition can be possible, having just run for multiple hours with no issue.
  2. Onboard DC voltage within the PS3 circuitry found its way to the frame, via a frayed wire, or something else.  I examined all wires in the vicinity of the motor that could carry DC, and none are frayed or kinked in any fashion.

 

I have disassembled this unit completely, doing numerous continuity checks and wire inspections as I go; with no fault detected.  At this point, I will reassemble the unit and check continuity as I go.  I have a spare PS3 board that I can use, and I will install a fast-acting fuse between the the pantograph and board for its protection.

The only other thing I didn't check thoroughly is the old board itself; that perhaps it shorted when the shell was shut, but I don't see how that could be given the arcing was elsewhere.

I honestly don't know what else to check.  I hate reassembling and re-testing not having found a definitive cause, but I don't see any point in having it sit on my bench in pieces.

Last edited by Pantenary

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