Some people install the speaker so it is firing up through the coal load. They drill small holes in the coal load and the a thin coal of glue with coal sprinkled on top of the glue. That way, the weight is not affected.
If you put the speaker on the bottom, you should add weight somewhere.
I have a Spectrum 4-4-0 and 4-6-0 and I know the wires in the tender do NOT follow the NMRA code.
Make sure you have a multimeter to verify continuity. If you just plug the decoder in to the PC board, clip the capacitors.
Some Spectrum tenders, the tender trucks can swivel around and cause a short when the loco and tender are put on the track.
I remember that the wires for both trucks are red. One truck picks up from the right rail and the other truck picks up from the left rail.
Good luck.
Rich
I have to correct myself. On the tender there are two connectors. The two pin one has the correct colors. Red & black.
The four pin one has different colors than the NMRA standard. If you hard wire the Tsunami, make sure you use a 1k resistor. I have installed the Micro-Tsunami in my Spectrums.
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Most fellas remove the Bachmann board. Litchfield station has decoder install tips:
http://litchfieldstation.com/DCC-University/install/HOSS/InstallationExamplesHOSS.htm
Also do a google search and you may find info that way as well.
One thing, make sure you mark any wires before you snip them from the existing board. I.E. which wire is the orange wire, which is the grey, which the red, etc. It will save you a ton of time and you won't have to scream as much.
Birdog