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How do I install a Digitrax DH121 decoder into a Rivarossi 2-8-8-2 Y6?

-- Alvie (al_cool5@yahoo.com), November 26, 1999



Merry Christmas! Here's hoping Santa brings you a sound decoder to install in your Y6.

Note: The decoder installation instructions does not duplicate information presented in the Wiring for DCC sections on sound or installing decoders in specific locomotives. Be sure you have read these first.

This is probably the easiest locomotive that I have installed a decoder in. If you are mounting a decoder in the tender, it is easy to get wires from the tender to the locomotive. There is also room for flickering firebox effects in the locomotive.

This is a generic decoder installation instruction. Any 1.5A or 2A decoder by any manufacturer may be used. I now am only installing Soundtraxx modules in my locomotives. Since the hook up for flickering firebox effects and if you install sound, the speaker as well, are the same regardles of locomotive, they will not be covered here. Only the specific hook ups for motor, power pickup, and headlights will be covered.


On the fireman's side is a screw off-center on bottom of locomotive. The rear powered truck may prevent removal. That's fine. It is only necessary to unscrew it enough to remove boiler.

Behind smokestack is a rectangular piece. Remove. Unscrew covered screw to remove boiler.


Though I bought all my Rivarossi locomotives within the same couple of year period, no two seem alike. My instructions may not match exactly. Your locomotive may not even be close!

If you have the fat black can motor that typically occupies the cab or even sticks ou the back, you need to cut the strap that connects one of the motor terminals to the case with your Dremel. Failure to do so will destroy your decoder! My Big Boy and 2-8-8-0 B&O are have this style of motor. I have seen a cab forward that was like this, too.


Remove pilot truck.

Remove existing wiring from motor to headlight. Remove exisiting headlight.

Remove screw in front holding cow catcher. You may have to pry to separate. Remove headlight. Replace with a grain of wheat bulb. Run wire out front where old bulb made contact. Thread wires into boiler.


Since electrical pick-ups are notoriously few on Rivarossi's, I have decided to no longer attempt to put chuff sync cams on Rivarossi's. I have found that it doesn't work perfectly when installed on a wheel without electrical pickup since it depends on the wheel that has the cam disk and one of the wheels that do pick up power to be making excellent electrical contact with the track at all times. If you mount the disk on a wheel with a electrical contact that pushes on the back side of the wheel, you may interfere with the locomotive's electrical pickup or the contact may wear the cam disk. I have therefore decided to simply use throttle sensitive chuffs on Rivarossi's. You are certainly welcome to use them if you wish.

For those installing sound, I installed my speaker aimed up through the "doghouse" on the tender. This was the first time I had not drilled large holes in the tender floor and aimed it down. I used my favorite oval speaker discussed in my section on sound. The primary reason for wanting to aim the speaker up is to improve the high frequencies. Aiming it down at the tracks attenuates these somewhat. The bell in particular might sound brighter and crisper facing upward. For high pitched whistles, they would be more shrill.

On the negative side, the openning under the doghouse is smaller than the openning I would create in a tender floor. This would limit the amount of sound a speaker could push out. In my case, the relatively large speaker I like to use would have it's efficency impaired. I still decided that I'd rather have it's efficency impaired than to put in a really small speaker that couldn't put out much sound at all under any conditions.

Though I don't have exactly the same sound module in another locomotive to compare to, I didn't notice a significantly better sounding bell. This module doesn't have a high pitched whistle so I could not judge it. It definitely isn't as loud as my other locomotives can be. It's volume is about what I like to run my locomotives at. So it's perfectly fine.

Should you mount the speaker under the doghouse? If you typically run your volume at about 9 or higher, no. This is not a clear cut thing. So please don't ask me, "I run mine at 8, what should I do?" In my mind, it's just as easy to drill some holes in the floor. So eventhough I'm happy with the doghouse sound, I will probably return to floor mounting. If floor mounting is ever problem, I'll use the doghouse. To me, it's not a big deal either way.


Some non-sound decoders may fit inside of boiler.

Remove existing wires from motor's terminals.

Use silicon adhesive to hold a grain of wheat bulb in place if you desire a rear headlight.

Wiring hook-up: RED: Front articulated truck power pick-up. BLACK: Rear articulated truck power pick-up. GRAY: Right motor terminal. ORANGE: Left motor terminal. WHITE: One wire from the front grain of wheat bulb. YELLOW: One wire from the rear grain of wheat bulb. BLUE: Common to the other wire for the front grain of wheat bulb, the rear grain of wheat bulb, and flickering firebox effects if you are using them.

-- Allan Gartner (wirefordcc@augustmail.com), December 22, 1999.

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