Odd electronics problem....any ideas?

[MidlandPacific]

OK: this morning I powered up my layout so that I could run my BLI mike around in circles for my infant son, who at three months is already interested in the sight and sound of a moving train. Everything ran perfectly on the main cab, so I decided to move a Spectrum Decapod on the second cab, which is a smaller and cheaper MRC Railpower 1300 - very basic, so I don't use it much.

Nothing happened. I switched the cab control over to my main cab, which has a voltmeter and an ammeter, and tried again - the ammeter showed a huge spike. I nudged the engine and moved it into a different yard track/electrical block, and discovered that it would run a bit roughly in reverse, but as soon as it ran forward the ammeter started to wobble and eventually spiked, stopping the engine and showing a short. I haven't had this problem before.

I then tried one of my brass engines, and it, too, ran for a few inches and shorted out. Then I tried a second brass engine, and it, like my BLI mike, ran normally. No spikes, no shorting. Most of this equipment has been sitting on the layout without running for some time, close to a month and a half.

Any suggestions on cause?

[TomDiehl]

Is this loco one of the ones that automatically selects between DC and DCC?

Are your blocks fully isolated (both rails) or are you using a common rail setup?

When you ran the different engines, did you have both cabs energized or just the one you were testing?

[Cthetrains]

you may have a bare wire touching a rail..

[twcenterprises]

OK, are you running DCC? Try running affected locos on DC only, turn the other controller off (cut the power off). I'd suspect a problem in the locos, but try to rule out any electronics issue first. That seems strange, 2 engines crapping out at the same time. If they still act up with only the MRC 1300 turned on, then time to start troubleshooting the engines. If they run fine, then we'll need to do a bit more testing to see what's up.

Brad

[areibel]

Weird!
I would have guessed something shorted in the Decapod, but then another did and the third didn't?
Process of elimination, if you have a test track I'd try both of the sluggish ones on there to eliminate any layout related problem. If you have a multimeter I'd start checking for continuity on the brass loco between the wheels and the chassis- I had one that the insulation broke down on one driver and kept it from running. Then try the Spectrum and see if it shows a short anywhere- maybe something in the decoder, another board, etc??
Kinda just shooting in the dark here, please let us know if you find anything.

[ICRR1964]

Bench test the one that gave you fits first and test the Pack unit after you unhook it, you may have a problem with your pack. I dont know how big your set up is, but check your track for some metal object touching both rails you left laying there. My daughter was helping me do some work on mine and left a small pair of tweezers laying on the rails that I did not know about once, and this gave me problems for about an hour before I discovered them. Let us know what you find out.

[MidlandPacific]

This is one of the reasons I love this hobby: you guys are great.

There's no common rail - all of the blocks are completely isolated (and I'm using DC, rather than DCC). I did all of the testing on a single yard track that was connected to both packs with a DPDT switch - trying to control for all of the possible variables. My Spectrums are a few years old - 2003 - so they're DCC-capable, but no chips installed, not a whole lot of mileage on them.

Checked for bare wires, and a quickie external inspection and spray-down with the compressed air can turned up no obvious dangling metal parts or wires.

I suspect a problem in the 1300, but it's never been terribly reliable anyway, and I'm going to have to do some more testing tonight, baby permitting. Will let you know what I find.

Thanks to all for the help and advice -