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I've got a 37971 culvert loader that was working just fine.  The "Transformer" terminals are wired to my accessory transformer, and the "Switch" terminals are wired to a SPST toggle switch.  I've also got an SC2 that is powered from the same accessory transformer, and configured for 6 accessories (no switches).  When I added wires from my SPST toggle switch to the SC2 ACC1 position in parallel (so the culvert loader could be turned on by the SC2 or the toggle switch), bad things happened.  First, the 10 amp fuse on my accessory transformer blew, so something was obviously shorted out.  And now, even after completely disconnecting the "Switch" terminals on the culvert loader, it's as if the "Switch" terminals are always connected, so the loader is always "on" when a train car triggers the IR sensor.  Otherwise the culvert loader still works (including the IR sensor).

 

I opened up the culvert loader and got that "burned electrical" smell, and indeed one of the traces on the small circuit board is burned (though not all the way through).  I'm assuming there's a transistor in there somewhere that is now burned out, causing it to act as if the "Switch" terminals are always connected.

 

But I can't figure out what caused this.  I seem remember there's something special about position 1 on the SC2 being connected to the SC2 power inputs.  Could there have been some kind of short circuit through that path?  Neither the SC2 nor the culvert loader specifically marks the "U" and "A" terminals from the accessory transformer, so I didn't take any particular care on which was which on either device.

 

Two questions:  Any thoughts on what could have caused this?  I'm kind of scared of position 1 on the SC2 now.  And does anybody know anything about the circuit board in the culvert loader, such that I might be able to replace a burned out transistor?  I can ordered a replacement circuit board from Lionel for $22.50, but it would be more satisfying (and cheaper) to find and replace just the bad transistor. :-)

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Originally Posted by MHK58:

 When I added wires from my SPST toggle switch to the SC2 ACC1 position in parallel (so the culvert loader could be turned on by the SC2 or the toggle switch), bad things happened.

That's where your error was.

 

The SPST switches hot, not ground like the SC-2 does.

 

To connect to the SC-2 and your SPST, you need to hardwire the "switch" connections "closed" or "on"(kind of like it is now after the failure). Leave the hot side of your ACC transformer connected to one transformer post, connect the other(ground) to the center common connection of the SC-2, and then connect either the "on/off" or "momentary" terminal of the SC-2 to the remaining loader connection. That will give you remote capability.

 

Now, take your SPST switch, and connect it to both terminals of the SC-2 that you are using. This will let you control it with the switch.

@Graz:  Indeed!  The "Switch" terminals on both the culvert loader and unloader don't carry power.  They are just a low voltage, low current, jumper across some of the electronics on the circuit board.  I just got out my voltmeter to see what's going on with my SC2 (which is configured for 6 accessories and 0 switches).  Positions 2 thru 6 are simple on/off as expected.  But position 1 seems to have the full 18 volt power on it.  So when I connected the "Switch" terminals to position 1, the full 18 volt power obviously blew out the culvert loader circuit board.   I've looked in the SC2 and Culvert Loader manuals -- there's nothing saying not to use position 1.  Graf -- did Lionel make good on this for you?

 

@gunrunnerjohn:  I guess cutting the trace solves this problem for position 1 on the SC2.  Have you ever seen anything in the Lionel documentation that using position 1 unmodified will smoke the Culvert Loader or Unloader?

 

@ADCX Rob:  Yep -- this is the way I have it hooked up now, since the "Switch" connections are effectively jumpered "closed".  So I have a workaround that's OK, except that the light inside the building doesn't stay on.  But previously, when the culvert loader was working correctly, hooking up the SPST toggle switch and SC2 in parallel on the "Switch" terminals will work as well.  If the toggle switch is "on", or the SC2 position is "one", then the culvert loader will operate, which is what I wanted.

 

I'm going to contact Lionel tomorrow to see what they say about this.  Seems like other customers could easily be running into the same problem unless there's a warning somewhere that I'm missing.

Last edited by MHK58

I hadn't yet had mine repaired as I wasn't completely sure of the issue. Now that I've read your post and the assessment, I would hope that they would cover the repair even though it's out of warranty.

Thanks for digging into this.

 

Are you going to cut the trace on your SC-2? Is there any real downside beyond the resale impact? I always use the AC wall plug for power anyway so I may make the cut as well.

Thanks,

Mike

 

To close the loop on this thread, Lionel agreed to fix my culvert loader.  It's been to Lionel and back, and it's now working again correctly on my layout.  They replaced the small PCB inside with all the electronics.

 

Interestingly, they also wanted to take the SC-2 for "modifications", after which they said it would be required to be powered from the AC wall plug.  That mod wasn't going to work well for me as I don't have AC power handy where the SC-2 is located.  So I did not get the SC-2 mods done.  I'll just be careful about using position 1, or I'll cut the trace per gunrunnerjohn's instructions.

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