bachman 4-8-2 plug pin outs(hard wire a decoder)

[lmackattack]

Does anyone know what the pin out is on the spectrum mountain. I am having head light troubles and I belive its caused from the circuit board in the tender. Im thinking I should just remove that board and hard wire the Soundtraxx decoder to the plugs for a cleaner instalation and remove any problems caused from the board.

Trent

[richG]

You can easily figure that out with a multimeter. If you are going to run DCC, a multimeter is a need.
Search the messages, Yampa Bob has posted some examples of tender wiring.

Take some photos of your project. Also, a picture of the PC board. Using the multimeter,
trace out the circuit. This can all provide info for others. No doubt some others may have the same or similar issue. Figure out if the loco has a LED or lamp.

Rich

[lmackattack]

the loco has a LED. I replaced it and it still did not work. I tested the soundtraxx  Decoder and the decoder gives the correct signal to its white wire but I believe its the bord in the tender is not passing along the signal. What I found was wierd was if I lightly press on the board the light sometimes comes on. Its almost like a bad connection but its not from a louse wire.  I will be glad to give out the info as soon as I jump in and test each lead. I was just checking to see if anyone has already done this as it would save me some time testing each plug pinout

Thanks
Trent

[richG]

Sounds like a cold solder joint or a crack in the PC board foil for the light signal.
Take a pencil that has an eraser and push on different parts of the PC board. Sometimes that can pin point to a possible area of the bad connection.

If I see this correctly, remove the 8 pin NMRA plug. With a multimeter probe on the pin 6 and the other probe on the connection where the wire leaves the board, you should see about 2,000 ohms resistance.

With a probe on pin 7 and the other probe on the other wire where it leaves the PC board, you will see about 600 ohms. Switch the probes and no resistance. Usually the blue or common plus lead has a diode in series. Maybe not all PC boards. Two of mine are like I have just described.

The resistor shows the same resistance with the probes in opposite sides.

Do you have the Spectrum USRA medium tender? I posted the electrical diagram of the PC board on my USRA tender.

The lead with the diode, you only see about 600 ohmswith the probes in one of two possibilites.

Rich

[lmackattack]

Yes this is the USRA medium tender. the loco in question is the I.C.R.R heavy mountain
What I was thinking is hardwireing the decoder to the plug leads and then installing a grain of wheat bulb to get rid of that blue LED. I like to run the layout in dim light some times and find the regular bulbs look better then the LEDs

Just my opinion

Trent

[richG]

Use a 1.5 volt lamps. They come in 1.2mm diameter size. About 20 to 30ma depending on manufacturer. Hardly any heat compared to the 12 volt lamps. Some people have melted plastic. locos using 12 volt lamps.
Here is an idea I have been following in the Yahoo SoundTraxx group. If you use a CL2 constant current device, the current will stay at 20ma when fed by anywhere from 5 volts to 90 volts. No resistor calculation needed. It is a LED driver. It can be used by 1.5 volt lamps also. Good for lamps that operate at 20ma. Some model railroad controllers operate above 12 to 14 volts and occasionally, someone has a burnt out 1.5 volt lamp because of that. Lamps are sensitive to voltage changes even with a resistor and the brightness can vary.
The CL2 is sold by Mouse Electronics. It is quite small.
I use  LEDs that are made specifically so you do not see the blue tinge. You can vary the LED resistor and accomplish pretty good results if you like experimenting.
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Another option I found in a different DCC forum.
The LM317 can be used as a current regulator using one resistor.
Look at National's application note.  They are available in the same
TO92 package as well as SMT.  I have used them with Miniatronics 1.5V
bulbs at just under 40ma as head and tail lights in trolleys.  They
operate for 12hr days during shows and have been in service over two
years.
With the SMT wrapped in Kapton I slip them in the boiler between the
weight and shell in brass locos, but they require good soldering
skills and don't drop them on/in the carpet.
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Please not, I have not done this. It was copied from a different forum.

Rich

[Yampa Bob]

Pinouts for the USRA Medium tender are listed in this thread. Wiring to a 2-8-0 also listed, the Mountain should be similar, but verify with an ohmmeter to trace the wiring.  Wire colors may vary, follow the decoder's instructions for wiring.

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

Most decoders, including Soundtraxx, follow the standard NMRA color code convention.

Good luck.