Tuesday, May 12, 2015

A Crack in the Cosmic. . . Diesel

A couple of things have been bothering me since switching the SW1 Switcher to DCC with sound -- the lights stopped working and the speaker in the cab was too big for the cab which kept the cab from meeting the chassis/frame cleanly.  That left a CRACK:
Front of cab doesn't meet chassis
After seeing an article in Model Railroading about DCC written by the DCC Guy, I checked the DCC Guy's blog and found a reference to "sugar cube" speakers (http://www.dccguy.com/?p=509).  Maybe that's the answer!  That led me to Streamlined Backshop website (www.sbs4dcc.com) and the purchase of the small 8X12mm speaker.

The next step was installation, and that meant removing the cab and hood.  What the heck, might as well check on the lighting while we're under the hood.  Using a 9V battery, a couple of patch cords, and about a 470 ohm resistor, I touched the connectors for the back light -- bingo, it worked.  So, now I was pretty sure I had wired the LED's incorrectly.


With the instructions for the Soundtraxx TSU-750 and a folder of DCC tips in hand, I cross-checked the wiring diagram with my wiring job:

I was pretty sure I used red wire on the positive side of the LED's, and the wiring tips say positive is blue from the decoder.  Oops, I have white connected to the red (supposedly positive) lead for the front and yellow connected to red for the rear.  Looks like they need to be reversed.  Plus, I need to replace the speaker.  So, some de-soldering is in order:
OK, everything pulled apart.  Note the size of the original speaker; not very big, but just big enough to overfill the cab; and there is NO space under the hood for a speaker.

Carefully (!! these wires sure are small) soldering things back together we get another jumble of wires:
I glued the sugar cube speaker to the top of the cab (you can almost imagine that you see it at the end of the purple leads) with white glue.  Hope it sticks!  Having a rounded cab top and a rectangular speaker didn't help the situation.  Lots more room this time.

Did that help with the CRACK?  I think so:
How about the lights?


Now they are even working correctly!  Amazing what correct wiring for an LED will do.  Seems I replaced the original front light with a "softer" light when I thought maybe the original had burned out.  Don't know when we'll be under the hood again so let's just leave it for right now.

I did note that the volume was significantly lower than with the larger speaker.  I turned up the volume CV's to almost maximum and the little Switcher sounds OK.  I read somewhere that most model railroaders run the volumes a bit too loud anyway.  Certainly on a small, 4X6' layout, you don't need much volume.  However, I'll have to turn the volume down considerably on the F2 loco to keep from drowning out the sugar cube speaker.  No problem.  Just a minor adjustment.

Bottom line, pretty pleased with results -- no crack, working lights, good sound.

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