Bachmann Spectrum N N&W Class J 4-8-4 Schematic

[oconnellpe2599]

I am trying to troubleshoot an issue with the front LED headlight on my N N&W Class J 4-8-4 loco. The LED works fine when tested, but when installed on the loco it does not light. As the output to this LED is through the 6-way connector, I assume the logic for this light is on the tender circuit board. I am looking for a schematic and/or feedback from anyone familiar with this issue. Any help would be greatly appreciated. Thanks.

[axle17921]

If you tested it without hooking a transistor hooks up to the positive lead you burned it out.  You should never test an LED with your power pack power unless you want to solder a transistor to do it.  LEDs are surge sensative and burn out on raw power, I didn the same thing I tested it with power and it lit but when I installed it it was gone, I had to replace it.  Also check the wires  on the harness in the tender, the wires break away from the plug very easily and you probrably wouldnt notice it go disconnected unless you really looked, also check the board in the tender, I had one with a sloppy soldering job done on it from the factory and some of the solder was "leaked" onto another circuit and was shorting the headlight out.  well good luck.

[skipgear]

I am trying to troubleshoot an issue with the front LED headlight on my N N&W Class J 4-8-4 loco. The LED works fine when tested, but when installed on the loco it does not light. As the output to this LED is through the 6-way connector, I assume the logic for this light is on the tender circuit board. I am looking for a schematic and/or feedback from anyone familiar with this issue. Any help would be greatly appreciated. Thanks.

Are you replacing the LED? I'm confused. How did you test it?

There are resistors on the "lightboard" in the tender that limit the current to the LED. An LED is a diode already so there is no need to additional diodes to control it but I believe that Bachmann uses them to control BEMF flicker. If it is just the LED is not working now after originally working, check the jumper clips on the light board. They aren't the best fit and if you disturb them, they get loose and don't make contact. Squeeze thim tighter. If you removed the LED to test it, did you re-install it with the correct polarity?

If you tested it without hooking a transistor hooks up to the positive lead you burned it out.  You should never test an LED with your power pack power unless you want to solder a transistor to do it.  LEDs are surge sensative and burn out on raw power, I didn the same thing I tested it with power and it lit but when I installed it it was gone, I had to replace it.  Also check the wires  on the harness in the tender, the wires break away from the plug very easily and you probrably wouldnt notice it go disconnected unless you really looked, also check the board in the tender, I had one with a sloppy soldering job done on it from the factory and some of the solder was "leaked" onto another circuit and was shorting the headlight out.  well good luck.

Axle
  A transistor is not needed to hook up an LED. All you need is a simple current limiting resistor. When testing an LED with a 12V power supply, a safe bet is between a 600 and 1000 ohm resistor.