Soundtraxx Sierra

Overview

(Many thanks to TOC (Dave Goodson) and Stan Cedarleaf for the information on this site about the Sierra boards)

Many people over the years just knew this product as the Sierra, and not from the parent company Soundtraxx, most known now for the Tsunami, a very successful DC/DCC sound and motor decoder, the first all in one decoder that changed the sound based on actual motor load, via BEMF.

The Sierra is an "old school" DC only sound system, that sounded good, but was a pain to program, and also often needed extra electronics when run by a PWM motor driver, and also often needed special eletronic isolation to run sound triggers from an R/C system. (see more on this at the end of the page)

Still, many people still love them and used ones are still out there.

Note the board might say "Throttle Up!" too. "Throttle Up!" is the parent company of SoundTraxx, and Sierra was the model.

Back side showing ROMS that have functionality and sound files:

sierra\

 

"Front side" where the screw terminals are:

 

sierra picture

Versions:

Apparently, all the Sierras have the same part number on the board (312023 or some such).

I don't have any pictures of Rev A.

Rev B has no mounting holes dated 1987

Rev C has four holes, dated 2000

Notes: (read before powering up)

One thing that is very important, this unit requires fixed polarity, it cannot be connected directly to the rails in a normal DC system. The manual is not clear on this, but if you look at the wiring diagrams that show ACTUAL track power circuits, you will see a full wave bridge rectifier between the track and the Sierra.

Also, there is no listing in the manual for all the screw terminals. There is a very problematic connector for the battery, and you can use the screw terminals instead. This is NOT in the manual, but it's true, Terminal 2 is ground and Terminal 4 is positive. You can kind of verify this by seeing that terminal 2 is used for the volume up down control, bringing terminals 1 or 3 to ground. You can also see terminal 4 is the common for lights, and this is normal in DCC decoders, the common for lights is actually positive. The point is using screw terminals to power the board as opposed to finding the small 2 pin power connector.

Important: Again, nowhere in the manual, but there is an upper limit for voltage. Will run all day at 12 volts. At 14.4 volts it will run for a short while, like a test run. At 16.8 a very short period of time, and instant destruction at 18 volts or higher. When it stops working, it is damaged, and it is normally the 4 lead bridge rectifier, and often burns the board enough to make it non-repairable.

 

Basic Wiring:

sierra steam Wiring

Programming / Application specific stuff:

A number of application notes were made, besides the Steam and Diesel manuals.

I have them in PDF form, email me if you need them.

Notes:

One thing that is very important, this unit requires fixed polarity, it cannot be connected directly to the rails in a normal DC system. The manual is not clear on this, but if you look at the wiring diagrams that show ACTUAL track power circuits, you will see a full wave bridge rectifier between the track and the Sierra.

Also, there is no listing in the manual for all the screw terminals. There is a very problematic connector for the battery, and you can use the screw terminals instead. This is NOT in the manual, but it's true, Terminal 2 is ground and Terminal 4 is positive. You can kind of verify this by seeing that terminal 2 is used for the volume up down control, bringing terminals 1 or 3 to ground. You can also see terminal 4 is the common for lights, and this is normal in DCC decoders, the common for lights is actually positive.

Sound revs up to max all the time:

Most modern decoders and other motor controllers output PWM (Pulse Width Modulation), which are full voltage pulses of variable duration. The motor sort of averages these pulses into an average voltage and the world is good.

But the electronics in the Sierra usually see these pulses that all go to full voltage, and disregards the duration, and there is no averaging. So often the sound unit, when connected to the motor, goes "full speed" all the time.

 

Sierra made some boards to help, although the board I have documentation on seems to more isolate the Sierra from the motor controller. It may be that this works to help the full speed problem, or it may take something else... not sure.

 

Soundtraxx19