There are six wires going from the locomotive to the tender: two for the headlight, two for the motor, and two for the pickup. Is that correct? I guess the tender drawbar is a redundant electrical path?
Are they color-coded, Jim? Or, are they all black?
Tom
Four are blue, one is bare copper wire, and the other is bare with blue stripes (yes, stripes).
Stripes are nice. Tigers like stripes. Bear wires on a locomotive, what will they think of next!
The tender is not a redundant path. It houses the decoder and and a speaker for the sound decoders. Most come with a PC board and a separate board for the decoder.
Bachmann has three steamers that come with a non sound decoder for the motor and lights and you plug in a separate sound “module” for a sound version.
The wires in Bachmann steamers and diesels do not match the NMRA colors. Some Bachmann tenders are wired differently.
Six wires. The two pin connector is for loco pickups. The four pin connector, two wires to power the motor and two wires to power the headlight. The front truck picks up on one side, the rear truck the other side.
A replacement set I bought from Bachmann a few years ago. No idea if this has changed.
Go to the Bachmann site where you will find a forum, loco diagrams and product info, plus the DCC documents.
Rich
If you have a circuit board in the tender that you plug the decoder into, remove the two chokes (coil things) and add a jumper where they were, then cut out the capacitor (no jumper here). If you don’t do these things, it may cause you running problems. They did on my Bachmann Shay.
You do not have to remove the chokes if they are not in the way. With the caps gone, the chokes are a moot point. The caps and chokes form a tuned circuit. With the caps gone, no problem. The resistance of the chokes is negligible. The decoder PWM will see the chokes as a straight piece of wire. I did some measurements with a Scope.
Many do see the chokes as resistors. A few minutes checking the color bands on the devices and you can see they are a few Microhenries in inductance. Mine measured about 5 Microhenries.
Some cannot handle a soldering iron and find that clipping the caps is an easy solution.
Yes, I know, that is a good way to start another argument.
Rich
You may want to check out this thread I posted awhile back. Feel free to ask more questions, I have done a lot of work with Bachmann locos and have used their tenders behind lots of other brands.
http://cs.trains.com/mrr/f/88/t/181314.aspx?sort=ASC&pi314=1
None of the wires are bare, the drawbars does not provide an electrical path. Yes, two are the motor, two are pickups, two are the light.
Not all tenders are wired with the same pin locations in the plugs, this is done because some locos have LED headlights, other 12 volt headilghts - swapping tenders would burn out the headlights in these cases.
But swaps can easily be done and the pins can be relocated in the plugs.
I have done a long list of Bachmann tender swaps, too much to list without a specific question.
Removing the capacitors as others suggest will improve slow speed performance quite a bit.
Remember, all of this applies to most all Spectrum locos made in the last 15 or more years as well as newer regular line locos like the Berkshire - not just what is currently available.
As noted by others, Bachmann uses color coded wires, but not NMRA colors. It is easy enough to ring out or physically trace out the wires on the tender end.
What model do you have and what would you like to do? I can likely describe the easiest way if I know what you need to do.
Sheldon
Thanks, but I should have said I’m in N scale, so I don’t have those plugs.
So I have N scale. If I open up the Bachmann N scale long-haul tender with my Soundtraxx decoder in it, I will see two yellow capacitors towards the front but behind the plug from the locomotive. I desolder those, is that correct? What do those capacitors do?
I know capacitors from an engineering standpoint store energy, and I know HOW they store energy, but I’m unclear how they will improve the slow-speed performance of my engine…
That does make a big difference, I don’t know a thing about N scale, and I don’t think most of the others that replied do either.
Sheldon
I believe the tender drawbar is a redundant electrical path for the N scale heavy mountain. There are six wires, so two of them HAVE to be electrical pickup from the locomotive, and the drawbar also has a very small diameter copper wire embedded into it that connects directly to the front tender truck pickups.
The caps and two inductors form a tuned circuit that are used as a filter. Remove the caps and the inductors are a moot issue. Some decoders are affected by this filter. There are many users who have found this out. This is mentioned on the Bachmann site also.
Rich
Wow, that should have been in the original question.
Rich
Sorry.
gatrhumpy, I hope that you got your wiring problem solved.
I was following this thread because I have several Bachmann steamers.
I guess that with the dominance of HO scale, N scale modelers (and all other non-HO scale modelers) need to mention this at the outset of their posts. Just another reason to consider a separate forum for HO scale versus other scales.
Rich
You mean with my Powercab? NCE still has not contacted me yet. I sent the thing into them for repair like 10 days ago. I called about six days ago to make sure they got it. Seems like they’re busy.
I may call Larry to see when mine would be getting repaired.
No, I was referring to the wiring harness, the subject of this thread.
Rich
Not really a problem per se. Just wondered if the drawbar carried a redundant electrical path to the tender, and I highly think that it does because of the six wires from the locomotive to the tender.
NOOOO!
Not those capacitors, those big ones are part of the sound decoder
The capacitors in question are very small, and across the motor leads. Some Bachmann locos have them on the circuit board in the tender, some have them right on the motor itself. These small capacitors are there to filter out RF interference (and in all my years I never had issues witht he TV or radio being interefered with because of my trains), and as such filter out higher frequencies. Such as the higher frequencies used in a ‘silent drive’ or ‘supersonic’ decoder. They also filter and change the shape of the BEMF signal that is used by the better decoders to maintain constant motor speed.
Yes, capacitors store energy, but for low values of capacitors, the time they take to discharge is microseconds. That’s how they are used in oscillators and filters for higher frequencies. For a capacitor to perform any sort of keep-alive function, it needs to be of a rather large value.
–Randy