There are two ALCo HH600 switchers at Fillmore.  They are Atlas models factory equipped with DCC & sound; that means they have QSI decoders.  Over the years I have had a bumpy relationship with QSI decoders, however they were working okay in these engines until after the operating session last December.

NYC 675 was on the layout and used for a refuelling operation as part of the engine terminal blackboard operations.  When I was putting away the layout, this engine did not respond although it was running (sound was on).  I tried a number of things and ultimately tried resetting the decoder in three ways without any luck – using the command station, using the BLI Address Changer, and using JMRI DecoderPro.  I had also tried to change the address using the Address Changer thinking somehow the address had changed to something else – the address did change to what I programmed, but the little ALCo still did not respond.

I decided to change the decoder in my two HH600’s to be in line with my policy of standardizing on Soundtraxx decoders.  I would install the new Tsunami2 ALCo Diesel.

Before ordering anything, I wanted to see if the PNP style board decoder would fit.  I happened to have one for a future EMD FT build and I used it to compare to the space I had inside the hood.  This style of decoder does fit with about ¼” clearance to spare at the cab end.  It is thinner than the QSI unit and does not have the dangling drum capacitor that can cause issues with fitting into a model.  In the picture below, I have the Tsunami 2 PNP board up against the chassis to show it’s relative size.


It was a simple matter of clipping some wires and removing the QSI unit (below).  It was very easy to make out which wire is for what.  The two wiring harnesses below are for the head light and backup light.  The two circular orange objects that are factory-soldered onto the motor are nothing to worry about.  I e-mailed George at Soundtraxx about them; I forget exactly what he said they are for, but I did not have to remove them.


In the picture below, the decoder is mounted….


…and the wiring connections soldered.



This was an easy project since the speaker installation is already factory made over the front truck.  Having a small (portable) command station, like my older Digitrax Zephyr,  is very handy for testing the models at the workbench.


The only issue was the headlight, but I reversed the leads and that solved it.  The back-up light mounted high in the cab, has factory installed individual slim quick-connectors so that the body can be removed from the chassis (thank you Atlas!).


I programmed the road number using my Broadway Limited Imports Address Changer.  NYC 675 & 677 were then programmed using JMRI DecoderPro and any changes made to pages were captured as screen shots and pasted in a document for this locomotive type.  Having a record of how a model was programmed is handy.

The Tsunami 2 Alco decoder didn’t have an option for the Model 538 prime mover that the HH600 had.  I selected the Model 539 Non-turbocharged choice.  The difference between the 538 and 539 is in how it was mounted on the chassis – the 538 being an engine design taken from a stationary power plant, thus the railfan high-hood name for these switchers.  The 539 was mounted lower for the subsequent S1/S2/S3/S4 switchers.  The prime mover sound ought to be the same.  Not knowing any better, I chose a basic Wabco (Westinghouse) horn from a long list of honkers and an ALCo bell run at medium-fast speed, amongst other customizations.

After my success in using the Sergent passenger uncoupling tool (for use where diaphragms do not allow the usual tool) on my EMC 103/103A Model F Demonstrator build, I decided to apply Sergent type E couplers to these engines.  I am determined to make Sergent couplers work on passenger cars with full diaphragms.

The coupler boxes were a bit shallow for the Sergent coupler shanks; I added strip styrene to make more space, below.


Above, also shows a Kadee washer on the left.  I adjusted the coupler heights using these (out of convenience).  I believe that Sergents are more forgiving than Kadees for coupler heights, but I still try to get them close using the Sergent coupler height gauge.


A very good book on the Alco HH600/HH1000 is ALCO’s HH SERIES (R.D. Cupper/D.R.Sweetland/P.K.Withers, Diesel Era, 2006).  It has pretty much the whole HH story in a manageable volume with lots of pictures.  It is in chronological order and details those locomotives made for specific railroads.  Also included is a chapter on second hand owners – these engines had extraordinarily long service lives.


Well, they’re done – they sound great and run excellently, especially smooth at a slow 1% throttle setting.