Tender back up light not working

[T Cline]

I have a brand new long vanderbuilt tender that I have paired with a 4-8-2 that I bought used. I noticed that someone had removed the light in the firebox, and spliced the wires to bypass that. Could that have anything to do with the tender rear light not working? I'd rather not have the firebox light, but I would like to have a working backup light. Any ideas?  Also, I am modifying the new tender, need to shorten it by about 10 HO scale feet and reconfigure the front of the tender. Without DCC, how critical is that circut board in the tender? I'm not sure about removing it just yet, but it would make the kitbash easier if it wasn't a factor. Why did they but half of the "brains" in the tender? 5 wires to the tender, is that really nesessary?  As I said, this is on a straight DC layout. I'm no electrician, but that seems like overkill to me.

[Yampa Bob]

First you should test the back up LED to make sure it is functioning. With your digital multimeter set to "diode" (the small arrow bottom right on the dial), touch the red test lead to the LED positive (+) terminal, the black test lead to the LED negative (-) terminal.  The LED should glow softly.

The rear LED is identified as LED-1 on the circuit board, terminals are marked plus (+) and minus (-).

You don't have a digital multimeter? Every modeler should have one, available here:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899

Alternately, use two AA 1.5 volt batteries in series (for 3 volts) with two pieces of small wire for test leads. Touch wires to LED terminals, plus to plus and minus to minus as above. The LED should glow brightly.

Another handy power source is a 9 volt battery with snap on connector set, but you MUST connect a 470 ohm resistor in series with one of the leads, otherwise the LED, if functional, will release its built in smoke. 

Also, hooking up a small buzzer (Radio Shack #273-055) in series with one of the 9 volt battery leads makes a very useful audible continuity checker / short detector.

Regards

[charlii]

Wire 18v grain of wheat bulb in series with a diode to contacts to metal wheels of tender. Bulb will light only with dc reverse polarity, if diode is turned correctly.

[Jim Banner]

... Without DCC, how critical is that circut board in the tender? I'm not sure about removing it just yet, but it would make the kitbash easier if it wasn't a factor. Why did they but half of the "brains" in the tender? 5 wires to the tender, is that really nesessary (sic)?

The power picked up by the locomotive wheels and by the tender wheels pass through the board on their way to the motor and to the headlight.  This is true both for dc and DCC.  If you remove the board, you will have to supply an alternate path for the power.  The board is there to provide an easy method for people to upgrade to DCC.  The wires are there to allow the board to do its job.

There are usually six wires - two to the locomotive wheels, two to the motor and two to the headlight.  If there is no tender pickup, then four wires will suffice.  Perhaps in your case it is four wires plus a fifth for the firebox light?

Could the LED being removed from the firebox affect the tender light?  Possibly, if the firebox light were an LED in series with the tender LED.  More likely, the LED is backwards if the locomotive's original tender did not have an adapter board for DCC.

By the way, telling us what brand of locomotive and tenders you are talking about would help.

Jim 

[Yampa Bob]

According to Todd's other thread, the tender is a new Spectrum Long Vanderbilt. Since the loco is used, its wiring may have been modified as there should be six wires.

If the previous owner hot wired the loco pickups directly to the motor and headlight for strictly DC running without a "ready" tender, the Vandy PC board may be completely "out of circuit". 

Todd: If you can remove the loco shell, please trace the wiring.  For proper operation with your tender, it should be wired as Jim described earlier. To help with the "pinouts", refer to the following thread, through the 6th post.  A Medium Vanderbilt tender is shown, but the circuit board should be the same.

http://www.bachmanntrains.com/home-usa/board/index.php/topic,7439.0.html

Let us know about the loco wiring for further help. Also advise us if the loco has the proper wiring harness with female connectors, to mate with the male connectors on the tender. The loco should have both a 2 pin and a 4 pin connector on the harness.

You don't need to be an "electrician", just hang in there and we'll walk you through with simple steps you can understand. However, you may need a small (15 to 25 watt) pencil soldering iron and solder. We'll wait and see.

[T Cline]

You guys are correct, I don't know why I typed in 5 wires, it does indeed have 6. I have the tender totally torn apart right now to shorten it by about 10 scale feet. I guess this would be a good opportunity to test the LED. I do have a multimeter, Is the red wire off the LED the positive? Also, are there any wiring schematics for Spectrum locos available for download?
Thanks guys,
Todd

[Yampa Bob]

Todd,
Unfortunately there are no wiring schematics available for Spectrum locos or tenders, that's why I posted the thread "Pictures and Diagrams". Please read it thoroughly, several times if necessary.

Every modeler should have a basic concept of the wiring schemes used in model trains, and know how to trace out the wiring. 

The wire colors are not consistent with any standard convention. As I mentioned in my first reply, the circuit board is marked + and -  for the rear LED. Just follow my previous instructions exactly and you won't have any problem.

Keep us posted.

[T Cline]

Thanks for the reply Bob, I certainly do have a basic concept of 12v. DC control, but I do get confused by these newer PC board setups.  Seems like overkill to me. Oh well, that's the price we pay for these newer models that are, in my opinion, much better than what we had in the 1970's.(and that's what I'm used to working on). I am tempted to just tear out all that PC stuff and straight wire it if I run into any problems. I guess having a back up light on the tender isn't that big of a deal anyway. I don't have any plans for DCC in the near future. But I will take a look at your P&D thread before I get the pliers and hacksaw out.

Todd

[Yampa Bob]

Todd,
Perhaps I can ease some of your confusion. Consider the PC board as nothing more than a "light board" for DC operation. 

Four diodes labeled D1 through D4, and some resistors labeled R1 through R5. These components provide directional lighting and current limiting for the LEDs.

Bachmann does add a few extra components for noise suppression, namely one or two capacitors and a couple of coils. These components are only required for European markets. 

Earlier light boards for DC were much simpler, often consisting of only 2 diodes for directional lighting. I agree the newer boards are overkill, but most modelers are stuck with them if they want "plug and play".

Keep in mind that LEDs are polarity sensitive. If the LED doesn't light when you test it, switch the probes and test again just to be sure.

[Jim Banner]

No need to install a DCC decoder just to make the lights work on dc.  Just wire a regular diode (e.g. 1N4001) across the LED but with the opposite polarity.  Then use a 1k resistor in series with that combination and connect the whole arrangement across the rails (via the existing pickups.)  The LED will light only for one polarity (direction of the train).  The regular diode is there to make sure the LED does not get too much reverse voltage.  If the LED lights for the wrong direction, simply reverse the wires to the rails.  This works for both the tender light and the headlight and takes up very little space in the tender.

If the word description of the hook up is confusing, let me know and I will post a diagram.  It really is very simple and costs much less than a decoder.

Jim

[T Cline]

Well, after putting the tender back together after shortening it, the backup light now works! Go figure...