Good afternoon all:

This afternoon I was running (2) E44s on a relatively short coal drag at 15smph, largely to break one of them in.  All worked well for almost 2hrs, then there was a sudden rash of arcing somewhere right around where the motor meets the frame on the aft truck of the lead locomotive.  The layout protection circuitry did its job and I popped the hood on the E44 for a look around.  There were no visible signs of arcing around where I saw it, nor was anything more then lukewarm.  However, there was a bit of an ozone smell around that DC motor area that was not on the other one.

I tested the DC motor in question by itself on the bench, and it apparently ran fine.  Seeing nothing else obviously amiss (or any pinched/frayed wires anywhere), I tried to run the unit again with the shell partially opened so I could watch the entire truck area closely at a very low speed.  It ran fine that way, but after the shell was shut by hand, (not screwed back together), some arcing returned.  Note the arcing was not internal, but right where the motor/truck meet the frame, or as best as I could see.  Regretfully, after the last arc, the unit no longer starts or draws any current.  The issue is not systemic, as all other locomotives work fine everywhere on the system.  So, the questions are as follows:

1.  Has anyone seen this kind of behavior, (arcing around where the truck meets the shell)?  I thought everything in that vicinity was the same potential, unless the motor itself is failing, which doesn't seem to be the case as it ran when bench-tested with no arcs or ozone odors, up to 10VDC.  There are no signs of arcing or burning anywhere on the offending truck, the surrounding frame, or the motor casing.

2.  Is there any protection circuitry on the PS3 module that could b e reset, or can I assume it is toast and/or needs board level repair?  There was no burning smell on the board, nor was any smoke observed anywhere.

(NOTE:  the pantograph feeds the PS3 module directly, and no rollers are used.  As such, the red wire on the truck is not connected to anything, and can't short anything out).

Any direction would be helpful, thanks.

--Nate Murry

Original Post

Sounds like a wire has a pinhole, and the shell forces it to contact the frame.  I had that on an RK GG1, and went nuts trying to find it--eventually did.

If the other end of the red wire is connected, it is live.

 

Hi RJR:

Well, remember that my locomotives are powered by the overhead.  There are no rollers, and the red wire that connects to the roller box on the truck isn't connected to anything.

In other news, I found the arcing site in yellow below.  The smell and a scrape of the area make it pretty obvious, and it matches where I saw the arcing:

However, I am at a loss as to why there would be short condition there.  The other truck touches the frame here (and even the other side of this truck), with no ill effects.  Like I said before, there are no wires that were pinched here, (that coupler wire was just in the way for this picture).  Obviously something happened to cause this, and I will find out why, but for now it mystifies me.

--Nate Murry

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That is the coupler wire and one wire would have constant DC Positive voltage present.  So it that arcs to the frame which would normally be carrying AC you can get arcing, and in worse case when return comes in contact with frame, ac power fed back on the PS-2 or 3 board and that usually means total damage to the board.

Coupler wires can be a source of that arcing if motion unaffected.  And as others have said, if powered via trucks the red center rail another source if the insulation becomes damaged.  G

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All:

Thanks for the replies.  I have mentioned some of the answers here and there elsewhere, but let me summarize again in case I missed anything.

The rollers have been removed, and the roller connection wires do not go anywhere.  As a PS3 unit, it came with a pantograph/roller switch, which I removed.  The pantograph directly feeds the PS3 board; there is no involvement of anything to do with rollers or their connections.  Even if I missed something and shorted the roller wire with the outer rail (which I already confirmed is not the case), it wouldn't matter, as the 3rd rail on my system is completely dead, and disconnected back at the control stand.  One can short the 3rd rail and outer rail during operation of trains, and nothing happens.  The 3rd rail can power coaches, but that requires a manual plug-in at the control stand to enable, and I rarely use it.  The system was specifically designed to make as little use of the 3rd rail as possible.  As far as the coupler wires are concerned, I did think of that initially and checked them for nicks.  I didn't find any, but as a confirmation, I disconnected the coupler on that truck completely, and there was still the same arcing on the next test.  Perplexing.

It appears that the frame is becoming hot somehow, and that point on the truck is the 'point of least resistance'?  I checked if there was any continuity between the pantograph and the metal in the shell, and then to the frame, and there was none.  I didn't expect that anyway, as the pantograph is mounted to an area of the roof that is all plastic.  Even if something was a miss there, why would it run with no problem for over two hours, then suddenly short out?

I have to be missing something, probably simple and obvious.  I am even re-checking some of what I already did, just in case.  Thanks again for the responses. 

--Nate Murry

I agree with GGG I'll bet you your board is now dead and you'll need another board, the problem is if you don't find what caused the short YOUR ASKING TO BLOW ANOTHER BOARD. you need to inspect thoroughly and if need be trouble shoot with a  ohm meter while moving  wires round no voltage applied just use ohm meter and see if you can get the short to show up  if nothing is obvious I would look on the frame area described for a arc deposit that was left. anytime there is a short where ac hits the dc on these boards there usually toast!

Alan

o gauge  trains ,music ,computer repair windows 7 and 10!

ASC Tech MTH school completed! 2019 !

Pantenary, I'm not clear on one thing:  is the red roller wire also disconnected up at the board end?  FYI, the pinhole on my GG1 was just that--so small I overlooked it many times.  I suggest a careful inspection of every wire and every wire joint, with a magnifying glass.  When the shell goes on, it may press on a connection or connector.

Hi RJR:

On PS3 electric engines (which this is), the red roller wire and a red pantograph wire meet at a selector switch on the frame, forward of the board assembly.  I typically remove the red roller wire and selector switch, and feed the board directly with the pantograph.

I have to test the board again to be sure it is dead, but GGG's idea of DC getting in somewhere makes sense (especially if the board is dead), but I still cannot see any frayed wires coming off the board or anywhere else.

--Nate Murry

I had a similar problem with a PS3 Trainmaster. Engine ran fine for about 8 months, then a small arc started underneath the engine. Over time it gradually got worse so I took the engine apart and found the arcing was happening between the truck and the frame where they come together. No arcing on the other truck. I could see pitting on the frame where the arc was occurring but couldn't find any cause. Eventually the engine just quit. Fortunately it was still under warranty so I sent it back to MTH and they replaced the PS3 board. It has been running fine ever since. I have no idea what the problem was but wonder if this was a known problem and MTH fixed it along replacing the board.

Ken

 

maybe one of the couplers the coil wire is grounding threw the coupler occasionally like someone said there is a hot on one side of the coupler coil the other end gets grounded electrical ground in board not chassis ground. I would get  magnification glass and with a very bright light inspect the whole area of where u suspect the arcing occurred!

o gauge  trains ,music ,computer repair windows 7 and 10!

ASC Tech MTH school completed! 2019 !

RJR:  Indeed, but its hard to tell, as it covered its tracks well aside from the arc area itself.

Ken:  What you describe is exactly what I am/was seeing, down to the exact arc site.  I have a few more continuity checks to try, and I do have a new board I can try eventually, (once I am confident there are no shorts anywhere else).

Alan:  Thank you for the tips, but as I mentioned above, the coupler isn't the problem as it was disconnected very early on in the diagnosis, with no improvement or resolution.  The arcing was the same as it was with the coupler connected.  Also, I already identified exactly where the arcing was happening (see the image above), and examined the site thoroughly.  There just isn't anything there aside from the coupler wire, which was shielded and intact, (and subsequently disconnected as mentioned). 

--Nate Murry

Some of this is too hard to follow, but you have an over head to get Center rail red wire AC power in to the board.  Where do you get outer rail AC ground from?  The chassis and the outer rail of the track?  Correct?  If so, you have a poor connection and you are seeing that arcing as the AC return to ground makes and breaks.  Dirty wheels or a poor connection via the black ground wire screws.  Or you do have Positive DC voltage making it to the chassis.  That can be Coupler, smoke element or Motor leads for a PS-3 engine.  Damage wire along chassis or heat sink, or at motor terminal/can.  G

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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.

--Nate Murry

Unless I have the wrong idea of the wheel arrangement, I can't see why there would be a difference of potential between truck & frame, when there is another truck making the connection.  I would not try another board, even with a fuse, as there;s too much risk.  If you think the board is bad, I'd recommend sending it to GGG to check it out on his test device.  In fact, it might be worth to ship the whole engine to him to find the fault.

IF the coupler wire is shorted on the truck you can get a DC voltage difference that will arc to the lower chassis AC ground.  They have the same ultimate return via the large bridge rectifier.  If the Wheels are dirty can get same effect.  If motor lead is shorting to frame might get the arcing to the truck.

It is either arcing because of an AC gap to bridge or the potential of high DC voltage on the truck or chassis.  Wires under the fake interior, or pinched under a motor, or chassis part like metal board bracket, or heat sink all viable issues. G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

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