Locomotive Stopped Operating

[WGL]

 I no sooner solved one problem than I have another.  My Intermountain F7A DCC with sound loco stopped working:  no movement, no sound & no lights.  The F7B DCC with sound unit works & was trying to push the A unit.
I've had the F7A for 2 1/2 months & bought it new.

[pdlethbridge]

Check for a loose or broken wire

[Yampa Bob]

Hey W.G., are we having fun yet? "Murphy" must really like you

[WGL]

 My Marx O locomotives cost much less than my HO ones, are almost 60 years old & have never needed repairs.  Also, they were probably made in the USA.

[WGL]

 I removed the shell & do not see a broken or loose wire.  I'm afraid that the next step is to remove the weight to look at wires under it.   

[WGL]

 My Intermountain F7A DCC with sound is working again!  Is it magic?  I could see no way to examine the connection between the red & black wires & the trucks.  Then, it occurred to me that, when the switch shorted out & stopped the power to all 3 locomotives, it might have disrupted the decoder in the F7A.  I decided to try re-programing it to its Address 1 on my E-Z Command Control.  I removed the other locomotives & set the F7A on the track.  I didn't need to do more:  its lights & sound came on & it ran!I put the other locomotives back on the tracks, including the F7B DCC with sound engine, & the F7A continued to work. 
  The remaining frustration was replacing the front coupler before replacing the shell.  I could have used the tiny fingers of a Hmong girl.
  Can any of you master hobbyists make an educated guess what went wrong & why it went back right?  Is there something to be learned here?

[Santa Fe buff]

Maybe you fixed something that was caught or anything when you removed the shell... Interesting... I guess wishes come true if you can believe. I sound like the Polar Express movie, but it seems so. Good luck, and that does sound weird...

Josh

[grumpy]

WGL
Unless you have a booster with your EZ Command you do not have enough power to use all the locos at the same time . The addition of the F7A with DCC and sound overloaded the system and it tripped the cicruit breaker . When you removed the other locos the demand from the F7A alone did not overload the EZCommand and it operated again.
Don

[WGL]

  I do have the 5 amp booster.  Do you have any other ideas?

[Hunt]

...
Is there something to be learned here?

Your next DCC system needs to be capable of resetting a decoder CVs to their factory value. Else, you will at times be faced with what can only be explained as happenstance. 

[WGL]

Hunt,
I guess that's two votes for the decoder (possibly caused by a short circuit in the defective switch), instead of the wiring.

[Paul M.]

Yet another reason I don't use DCC. ;-) BTW, how big is your layout? 5 amps is probably enough, but you never know...

[WGL]

 I run 3 DCC trains on 3 tracks connected by switches:  42', 39' & 36'.

[WGL]

 Intermountain eventually did reply to my e-mail & offered to repair or replace the locomotive.  When I replied that it is now working & asked what the cause might have been, he replied:

"I'm not really sure what the issue is. Layout short circuits can cause strange things to happen with sound decoders.

If there is a short in the rails, the DCC command station shuts the power to the rails off. It will try every 5-10 seconds to restore power automatically if the short was weak. If the short is still there, the command station will keep the power off until the short is cleared. Larger amp shorts will shut the power off until you intervene and press a button to restore power. If the short is still there even after you press the button, the system will shut back off. Track power can only be restored if there are no short circuits. If the system is shutting track power off automatically, there is a short circuit somewhere.

The other thing is that if your DCC system does not send out information to the decoder constantly, called a packet, the decoder will not respond. This means that when you first place the locomotive on the track the locomotive may act like it isn't working. When you give it a command to move it will "wake-up". This is because a packet was sent to it. The locomotive will shut down any time the command station stops sending packets. I'm not sure if the Bachmann DCC system works this way or not. I can tell you that it is at the absolute lowest end of DCC system quality. As such it does not have many of the hidden features that the higher end systems have.

Your situation could be a combination of the track short and then the packet not being sent to the decoder. The other thing it could be is if you have too many locomotives on the track. The Bachmann DCC system has only 1 amp of available current draw. This means that it might only take 3 or 4 sound equipped locomotives to max out the capability of the system and it will simply shut down. This may be why your A unit came to life when you removed the other locomotives. Just because the DCC system can "control" 10 locomotives doesn't mean all 10 can be on the track at once. The higher end DCC systems give you 5 amps of available current which allows you to control around 15-20 locomotives. You can also create DCC blocks to give you control of even more locomotives if your layout is large enough. Most DCC systems have the ultimate ability to control a minimum of 250 locomotives with the right set-up.

If you ever need to reset your sound equipped locomotive, you can easily do it without programming. Find the thin silver cylinder in the package that your sound equipped locomotive came in. Note the red marked end. Remove the shell from the locomotive. Place the locomotive chassis on the track with the power OFF. Locate the horizontal clear glass tube (reed switch) immediately behind the square black "chip". This chip is surrounded by a brown plastic holder toward the front of the circuit board. You may have to move some wires to find it. Once you locate the glass reed switch, place the red end of the silver cylinder directly on the reed switch. Turn the track power ON. Wait 5 seconds. Remove the silver cylinder. Wait 5 seconds. Turn the track power OFF. Wait 5 seconds. Turn the track power ON. The locomotive should operate on DCC address 3.

In the end your situation could be caused by just about anything and without actually being there to witness the events, it is difficult for me to diagnose the exact cause. Just be extremely careful with your track and switches to prevent short circuits and limit the number of locomotives that are on the track at one time and you shouldn't have any issues."

  Since I have the 5 Amp Power Booster, insufficient power was not the problem.