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There are a lot of older MDC/Roundhouse kits and ready to runs of the 2-8-0' and 2-6-0's that can be brought up to speed in the modern world. The MRC unit in the new ones dies.  Observation showed a Soundtraxx Tsunami could be fitted into the MDC old timer tender with two 1.1 diameter speakers.
Improving electrical flow
The Roundhouse locomotives were originally setup with the old tender-locomotive divide of electrical pickup. The addition of pickup on all the tender wheels proves to be a big improvement. Pickup on the locomotive has not been necessary even while running over dirty Atlas Code 100 dead switch frogs.
Blackening the backside of the wheels presented a problem, the slippery nickle plating wouldn't blacken. Chemical blackening was tried and failed.
Neolube a dry film graphite conductive product was tried but it too would puddle and would not adhere.
Various grades of sandpaper were tried to rough the slick plating. 320 grit worked the best and the Neolube adhered quite nicely. Wrap the sandpaper around a wood coffee stirrer.
Rough the backside of the wheel while holding it in the truck frame. The sandpaper should be used to produce a uniform field of light scratches.
Paint the Neolube on with a stiff brush. Let it flow onto the wheel back. Test the adherence by rubbing the surface with a soft stick.
The Neolube gives a flat black electrically conductive surface to the back of the wheel.
Kadee #5 coupler centering springs are bent to shape to be used as wheel wipers.
Cut the detail off the truck bolster and file the surface flat.
Crimp the "hole" end of the coupler spring around the bolster.
Drill a clearance hole for a 00-90 screw in the wiper and tap the bolster. Putting the spring on a piece of wood makes it easier.
Mount the wipers one side at a time. Test for electrical flow and free wheel movement. Use 1/4" long screws to facilitate the wiper being removed from the wheel while remaining screwed to the bolster. The wiper should make paths in the Neolube.
Solder wires to the wipers and connect them to the motor. Put a piece of shrink tubing on the bottom lead of the motor to make sure of not shorting. Now the locomotive can be test for sure mechanical running before the Tsunami decoder is intalled. Only tender pickup is used, if more pickup is desired a PC board bottom plate can be applied to the locomotive and wipers fashioned to pickup off the drivers.
Mounting the speakers
The MDC tender frame is a flat panel. A piece of 1/16 thick printed circuit board was chosen because it is rigid and a composite. A composite is less likely to have a resonant frequency interfering with the speakers. A piece of 1/8x1/4 plastic is used for the centersill.
A hole pattern template is used to locate the holes on the centersill. Mark them with a center punch.
Click here to download the hole template drawings
The centersill is assembled to the pc board with 2-56x3/16 long flat head screws.
Cement the template to the frame and drill 3/64 diameter pilot holes after center punching the locations. Drill out the holes with the corresponding drills.
The finished tender frame
Use the template to locate the circuit board cuts. After laying them out use a cut off wheel in a motor tool to cut through the copper isolating the areas.
Cut out a template and locate the speaker locations and use silicon caulk to attach the speakers.
Speaker Selection
I have found that using two different speakers gives a better sound. One should be a full range speaker with a maximum range of frequency response and one should have a "mid-range" frequency response.
Mouser Electronics has several 1" diameter speakers that are low profile and would work well. They have no minimum order and lower prices than the DCC suppliers.
I am using a speaker that came with an early MRC sound decoder and one left over from the 1980's when I was using Onboard analog sound.

Remove the fuel cavity from the tender. Use this style cutter in a motor tool. It works really well.
Using a template locate the hole locations and glue lugs to the tender shell for the 0-80 mounting screws. I use Accumate Proto:HO couplers and the template drawing reflects their use.
Assemble the sound decoder soldering the purple leads to the speaker terminals in series per the Soundtraxx Installation Guide. Put the harness wires through the holes in the floors. Red and black power in the back holes and the grey and orange in the front holes. My decoder is upside down so the leads are reversed from normal.
Since the old MDC/Round house Oldtimers had a solid boiler no light circuits were used and those wires were cut back from the harness.

Solder the leads to the corresponding pads on the floor. Test the sound at this point.
Make a new drawbar with a hole spacing of 1/2 inch from black plastic.
Mine is from an old tender shell.

Make mounting lugs from brass shim stock. Mount the with 0-80x1/16 roundhead screws. Solder the motor leads to the lugs. Run the locomotive to see if the drivers run in the correct direction.
Solder the wiper wires from the trucks onto the PC board tender floor. Make sure that the wires in the front do not go over onto the motor pad. Leave enough slack in the wires to remove the trucks.
Place a temporary piece of masking tap over the opening to seal the tender shell and make the shell a sound box. The installation is done and all that is left of the tender is cosmetics.
In the installation be careful of the tender steps, they break off easily. I used one in the "alpha" installation with a broken step because I knew I would break one off.

Great sound!

Not only does the Soundtraxx Tsumani give great sound, the up to date electronics gives improved performance over regular DCC.  My 2-8-0 is a much improved performer. It has slow speed performance that makes it an outstanding switcher.
Any questions about the overheating of the decoder because of tight spaces was dispelled. I have operated the decoder equipped locomotive for over an hour steady and it doesn't get warm.

We will be adding to this page shortly with electrical pickups on the locomotive side.

Grind two slots into the frame around the cab mounting lug. These will allow the original mounting system to be used. They do not have to be more than a single wire deep. This is the backend of the new 4-4-0 which has six wires to hide.
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