Did I burn out my engine decoder?

[sjackobs]

I just received a brand new, DCC On Board three-truck Climax today.  I run DC mode only and have no plans to run DCC.  The engine ran well for a few feet around a test loop of snap track.  The terminals on the snap track accidentally shorted out, and the engine stopped.  After I corrected the short, the engine did not function any more.  The lights did not light, and it did not move.  The tender was warm.  A DC engine ran fine on the track, so I know the power pack was providing power.  When I let the Climax cool about 10 minutes, and put it back on the track, it still did not move or light.  I heard very faint electrical crackling sounds from both the snap track connector and the tender, and the tender began to warm again.  Might it reset eventually?  Did I damage the circuitry irreversibly?  Will it run in DC mode if the dummy plugs are installed in place of the decoder?  If so, how do I reach the decoder socket?  Or should I sent it back to Bachmann?  Any help would be appreciated.

[sjackobs]

I answered my question and solved the problem.  Yes, I burnt out the decoder.  Yes, replacing the decoder with the dummy plugs allows it to run in DC.  Are DCC On Board engines generally this sensitive to a short in a DC system?   

[richg]

I answered my question and solved the problem.  Yes, I burnt out the decoder.  Yes, replacing the decoder with the dummy plugs allows it to run in DC.  Are DCC On Board engines generally this sensitive to a short in a DC system?   

Not that is have ever seen so far.
A WAG, if the loco was on the track when you removed the short, the power pack, "might" have shot up suddenly to a higher than normal voltage for an instant than normal but that is only a guess. The decoder no doubt got hit with a large current surge which can wipe out the full wave bridge rectifier, about the first electronics in a decoder.
You probably known now, but do a better job for layout wiring when running DCC.

Rich

[Rangerover1944]

Don't feel too bad, this DCC stuff is a learning curve. I've been back for 7 years, during that time, went to DCC and still make mistakes. I've "fried" 3 decoders by erro of my own making, out of many decoder installs during the past 7 years, some very difficult, but non the less, successful. Just recently, 2 days ago, I put a simple 2 function decoder in my pre-war Penn 4-6-2 steam loco, had all the wires connected except for the reverse light wires, which were stripped for solder in the tender. I was just testing the loco itself without the tender, with just the chasis on my program track, with those 2 light wires, flopping around, and disaster, they shorted on the live track. Lucky for me it wasn't a sound decoder. The sound decoder is in the tender seperate from the motor decoder. But it's under warranty, TCS replaces them even if I mess it up. Happy RR'ing. Jim

Lesson 101-don't strip'em, till yur ready to solder'em!

[Jim Banner]

sjackobs, you just described how ignition coils fire spark plugs in cars.  When a current passing through a coil is interrupted, the magnetic field in the coil collapses, causing a high voltage to be generated.  With the track shorted at the connector, there was undoubtedly a large current flowing through the transformer in your power pack.  When the short cleared, the inductive kick of the transformer was applied across the rails.  Most likely this kick or spike exceeded the about 30 volt maximum voltage of the decoder and something in it failed.  So far I agree with Rich.  And I too think the first component that probably failed was a diode.  But not from excess current.  More likely its reverse voltage rating was exceeded and it shorted out internally.  This would account for the overheating when you reapplied power.  With a shorted diode, the microcontroller in your decoder would be powered by ac which would addle its innards within a few milliseconds.  Without a working microcontroller, your decoder would be brain dead.

Jim