Steam MU Box

The MU box we have for the 765 controls:

1. Engine Run - Emergency Stop
2. Generator Field
3. Reverser (3-position rotary switch)
4. Throttle (9-position rotary switch)

Here's what it looks like...

The two lights at the top are to show wheel slip and the alarm bell. A third light is being added to show when the PC Switch is tripped.

The circuit breaker at the upper right is for the HOTD - the Head of Train Device, which is what communicates with the EOTD, the End of Train Device hung on the rear car. That is a separate device that is powered from this box.

The large, gray connector at the bottom right is where the 27-conductor MU cable connects. That is the cable which runs back to the rear of the A-Tank and connects to the diesel.

Forum member Hot Water had this box made for us when he was at EMD.

Thanks for posting the pic, Rich.  I'd been wondering what those boxes looked like.

Where do you put in the quarters?.....     Question...If that unit fails or just needs general servicing, will EMD handle that for you guys or are you on your own? 

There's not much to fail inside the box. There are no "electronic" components to fail, other than the two light bulbs. The box is just a group of wires and switches, that's it.

EMD would not be involved in any servicing, upgrading, etc. on this box. We're on our own, but it's not all that complicated inside.

The control of dynamic brake from the EMD designed MU Control Box, was NOT recommended by the Electrical Control Group of the EMD Engineering Dept..There were/are too many potential dangers involved:

1) The operator could inadvertently switch the trail units into dynamic brake WITHOUT switching out of power, since there are NO mechanical interlocks as there is with an AAR controller mechanism.

2) Power to any load indicating ammeter is HIGH VOLTAGE, and should NOT be run through the 27 point MU train line.

Thanx for the photos, info and commentary, Guys.  I've often wondered just what that "black box" I had heard about, actually looked like.  Pretty amazing that you can control a huge, powerful diesel lokie from what looks like such a small and, apparently, simple device.

'course, I'd still rather see any of the main line steam engines operating "solo" without the scene spoiler of a modern diesel tagging along behind.

Paul Fischer

Silly question but why Light bulbs in this day and age of long lasting LED's?

The box has Forewrd-neutral-reverse!  That means the helper engine has an e-unit in it!  (just kidding).

In the case of a mainline steam train today, would there be any need to have access to the d/b of the diesel?

TheMU Control Box was designed, and the first one built, in 1976, thus the small 64 volt bulbs. 

If it ain't broke, then why F%^& with it???? 

Absolutely!When ever the UP steam locomotives go out west, there are VERY long & steep mountain grades to climb and descend. 

The same applies to 4449 trips, when we do those 2-day trips to Bend, OR. We have to come back down the Deschutes River Canyon grade, thus we use the DB on the Amtrak unit.

Later this summer, NKP 765 will have to descend Horseshoe Curve. The DB will be used there also.

And it works as well as "The Cone of Silence" in Get Smart. 

What does?  The box or DB?

???Simplistic fail safe???. Each switch closes for control,  worse case the right side circuit breaker is turned off or you unplug the tether to open all circuits. Open all circuit the diesel shuts down/idles ???  Just asking the question from what I see?? 

Pretty close, Mike. Since the power (74 volts DC) for the MU Control Box, comes in on the #13 train line wire in the 27 point train line/jumper cable circuit, un-plugging "everything" pretty well drops any trailing units out of load since the "generator field switch" supply is killed.

That circuit breaker on the right side has nothing to do with MU control. It is just the ON/OFF power switch for the HOTD, which we do not often use.