This engine’s tender is pretty small, despite the totally incredible “23,000 gal” marking on the back of the tender. To have room for a speaker and a mobile sound decoder I think I’m going to have to wire the decoder directly to the tender connectors, and bypass the Bachmann circuit board. Haven’t been able to find a wiring diagram on the Bachmann site. Does anyone have a diagram or photo delineating which wires are which in the two pin and four pin connectors?
I assume this means I’ll have to wire appropriate resistors in line with the headlight and backup light wires - not sure of the size: would 330 ohm 1/4 watt be OK?
Does anyone know what the two small inductors are for on the Bachmann PCB?
Remove the DC adapter or decoder. Get the Tsunami and cut back the shrink. Remove the 9 pin connector with the wires on it. Get the 9 pin to 8 pin adapter. Plug in the decoder to the PC board. Install the speaker. Tuck the capacitor in somewhere. You can shorten those wires also if need be.
You can also shorten the wires and solder them to the 8 pin plug.
There is room. Others have done it.
The recommended decoder and speaker in the below link.
Be aware, Bachmann does not use the NMRA recommended wire colors. Get a multimeter and use the resistance scale to ring out the wires. Follow the NMRA wiring standard for DCC installs.
Bachmann has had 12 volt light bulbs in their 2-8-0 in the beginning. Don’t know if yours has LED or light bulb.
If you keep the PC board, not an issue.
Also, be aware if you change tenders, they wiring “might” not be compatible. I and others have found this out.
LED Resistor Values in case you remove the PC board which I do not recommend
Measured with 12.2 VDC supply using 20 ma max current LED’s. Values will vary a ittle depending on actual DC supply value.
Be aware, Bachmann does not use the NMRA recommended wire colors.
Boy howdy! It sounds like they don’t even follow a standard practice from one locomotive to the next.
Get a multimeter and use the resistance scale to ring out the wires. Follow the NMRA wiring standard for DCC installs.
I have a multimeter - but all the wires from the plug to the PCB fractured at the solder joints after just a few moves testing the fit with an NMRA plug and the Soundtraxx LC series decoder, so I do not have a clue on how to determine what wire from the orange tender plug corresponds to what pin at the NMRA plug, other than that the 2-pin plug seems to be the power pickup leads from the locomotive. That leads me to believe that the remaining wires at the 4 pin plug (2 red, 2 black) are the motor leads and the headlight leads. Bachmann’s catalog picture of the PCB does not show the bottom side where the wires from the 4 pin plug are soldered to the PCB, and I do not know if I can rely on the 4-pin plug to PCB relationship shown for those wires in the exploded parts list drawing.
Any ideas how to distinguish headlight from motor, and how to determine the correct polarity, without disassembling the locomotive? If anyone has a 2-10-0 PCB and could photograph the bottom side connections that would be a big help.
The LC decoders are older and relatively large, and the Decapod tender has limited vertical clearance made even tighter by the bottom of the coal bin, especially with a decent sized 28mm speaker in the tender floor, so I really think I need to hard wire the decoder to the tender plugs. I’ve considered using a male-female NMRA plug pair with the female plug wired to the tender plug and installed in the coal bin bottom, so the male plug from the decoder could be plugged in from underneath. And all with plenty of slack in the wiring
You can do the same with the Bachmann decoder. Remove the plug and solder it to the decoder wires.
I have the LC decoder and Tsunami decoders. They are the same size.
He puts the speaker under the coal load and drills tiny holes up through the coal load. Many do this. Glue some styrene in the speaker area for a tighter it ti isolate the sound waves from the front and rear of the speaker.
I ring out the wires with a multimeter in mine and document where they go. The NMRA has standard wiring specs for decoders.
If the loco runs in the opposite direction from what you select, just reverse to two motor wires.
The diodes on the PC board are for contant lighting. I think four diodes for headlight only, six for headlight and tender light.
This is over a year later, and don’t know if you ever got the answer I thought you were looking for. I was just browsing the web for an answer to Bachmann’s wiring in the 2-10-2, so I took one apart farther than I wanted just to answer the question.
FYI, I always remove all the Bachmann tender circuitry, so I DO need to know which wire is which in the harness, but I had forgotten since my last conversion. This is for the HO 2-10-2 non-sound only. I can’t vouch for other models or the sound version.
Two-pin plug is Rail Right (black wire) and Rail Left (red wire)