Lokpilot 54650 install/short questions

[mu26aeh]

I tackled installing a Lokpilot 54650 into an Atlas GP15 today.  I milled some of the frame away between the frame contact points to accommodate the wider portion of the decoder.  I taped off this area of the frame to protect from any shorts on bottle of the board.  I ran wires from the motor tabs to the motor pads on the decoder.  Programmed decoder, values accepted, put on test track, ran fine except lights were opposite of direction.  I took back apart and flipped the wires, lights now work correctly with correction direction.  But new problem arose.  When engine is on the track, throttle is zero, everything is fine.  The second I move the throttle, a short is detected and shuts down.  Using Digitrax Zephyr on my workbench.  Putting engine back on programming does not show anything, reads and writes to the decoder fine.  Looking for help on what to do or look for.  TIA

[tehachapifan]

Maybe there's now a solder bridge running between the motor contact pads or one of the motor wires is exposed and shorting on one of the pads or other part of the decoder or part of the frame?

Also, could one of the motor tabs be making contact with the frame once the board is in place? I don't have a GP15-1, but I have other Atlas locos where this is a definite possibility if they get bent or misaligned. This type of short often ends with the demise of the decoder, so it's hopefully not this one.

[mu26aeh]

now I'm confused.  I took decoder out, put original decoder in.  reads and writes, put on test track, calls up, lights on, changes directions but no movement.

Tehachapifan, I removed the motor tabs and ran wires from the caps to the pads on bottom of the board so no bending or misalignment    I looked for a bridge but can't see anything that would be a problem.  I even entirely tore everything down, and redid with new wire etc, and have same result

[Steveruger45]

When you slide the decoder into the frame it is possible that the solder mask on the bottom of the decoder has been scratched by the frame and causing a short with the frame. If this has happened you may need to file that area of the frame a little more and place a piece of insulation tape on the bottom of the decoder to protect it.

[woodone]

Have you tried to run the motor on DC (no wires to the decoder!). I don’t like soldering to the brush caps. Takes a lot of heat to get solder to flow and some times you can destroy a motor.

[Steveruger45]

Woodone makes a good point.  I try not to solder direct to motor brush caps as well, at least if you do be quick with the soldering iron or remove the cap holding the brush and brush spring in first being careful not to loose the brush and it’s spring.  Alternatively solder to the tab of the motor cap, again be quick with the iron.
To see if motor is damaged, With the motor not connected to anything Check for an open circuit or dead short across the motor, brush cap to brush cap, with ohmmeter set on lowest resistance setting say 0-200ohms, there should be a small resistance if it’s good.

[peteski]

Yes, the motor should be tested by itself. Checking its resistance (if you have a multiumeter) would be good first step. Or try running it from a DC throttle or even a 9V battery.

And I'll add another voice discouraging soldering leads directly to the brush holder caps.  The plastic used for the brush-end of the motor melts really easily.  Even just leaving a short (1/16") piece of the motor's contact strips and soldering the wire to them is much better than soldering directly to the brush caps themselves.

Here is an example of soldering wires to trimmed strips (not to the brush holders themselves).

[mu26aeh]

An update of sorts.  I tore motor/locomotive back down to start over from square one.  I took caps off to inspect, found one of the brushes to be jammed up inside the cap with spring.  I replaced that with one from a spare motor I have.  Motor did not run with old cap/brush via a battery.  Now runs via battery with new cap/brush.  When I soldered wires direct, I removed the caps from the motor to prevent the melting of plastic/ruining of motor.  I reassembled and tested with battery.  Engine runs.  I installed old Digitrax board.  It reads, writes on programming track.  Placed on test track, lights come on, switches direction and runs in both directions.  Took old board out, replaced with ESU board.  Reset board, reads and writes correctly on programming track.  Place on test track, dial up address 1444, hit 0 for light, comes on.  Switch direction, lights change direction.  Turn throttle from zero, short appears, light flashes in chorus with buzz.  Return throttle to zero, short goes away, no buzz and lit returns to solid.

[mu26aeh]

Idea dawned on me this afternoon.  I have Intermountain SD40-2s that have the slide in decoders.  I grabbed one and swapped the decoders.  I get same response there, so I emailed ESU about repair/replacement/exchange.

[Steveruger45]

Glad you found and fixed one issue at least.  I think you have pretty much confirmed now that there is a short on the esu decoder involving the motor circuit, at least when it is installed.  Check out the attached link to Peteski’s detective work on these decoders.  It might help in trouble shooting.

https://www.therailwire.net/forum/index.php?topic=44324.msg569570#msg569570

I’m thinking there is a short either across the motor pads or between a motor pad and the frame pad on the decoder or they get shorted on fitting it in the frame.  From the drawing you can see how close those frame and motor pads are.  I’m also thinking the decoder is probably toast.  Good luck.

[Steveruger45]

Idea dawned on me this afternoon.  I have Intermountain SD40-2s that have the slide in decoders.  I grabbed one and swapped the decoders.  I get same response there, so I emailed ESU about repair/replacement/exchange.

You just pipped me at the post with above.  Yep, if you got the same response on fitting the suspect lokpilot into a good sd40-2 you have pretty much nailed it to a toasted decoder.   ESU’s. customer service is excellent.  They’ll probable send you a new lokpilot.

[mu26aeh]

Glad you found and fixed one issue at least.  I think you have pretty much confirmed now that there is a short on the esu decoder involving the motor circuit, at least when it is installed.  Check out the attached link to Peteski’s detective work on these decoders.  It might help in trouble shooting.

https://www.therailwire.net/forum/index.php?topic=44324.msg569570#msg569570

I’m thinking there is a short either across the motor pads or between a motor pad and the frame pad on the decoder or they get shorted on fitting it in the frame.  From the drawing you can see how close those frame and motor pads are.  I’m also thinking the decoder is probably toast.  Good luck.

I'm guessing it is something between the motor tabs and the frame contacts that are right next to each other on the bottom.  I cannot see anywhere that the board was scratched or anything. 

[tehachapifan]

I'm guessing it is something between the motor tabs and the frame contacts that are right next to each other on the bottom.  I cannot see anywhere that the board was scratched or anything.

I'm still inclined to think there's something going on with the motor pads too. Is there any chance the frame itself is making that bridge once everything is tightened? Aside from this, maybe a piece of conductive debris is lodged between some components on the top of the board somewhere?