Work has continued on the sound decoder installation (Digitrax DN144 in an Atlas GP38). The first test run, with the decoder and speaker wired, but still "hanging loose" on top of the naked frame, revealed a problem (problem #1). The sound came on alright, but when moving forward the engine stopped and went silent, while first issuing three short beeps. It did not really stall. It more of made a controlled shutdown of itself.
If the engine was left were it sat, and with the throttle untouched, it soon started to move again. But after having picked up speed it stopped again. The problem went away when the sound was turned off (F8).
After some head scratching and some more test runs I finally decided it must be a power pickup problem. Apparently the deocder is fussier about uninterrupted power when the sound is on. Meticulous track cleaning made things better, for instance.
Time to install the capacitor, which I had so far left out of the equation. This since I could not figure out where to install it. But I could always solder it in place for a test run with the shell off.
Problem #2, the black capacitor wire was all of a sudden gone. Must have broken off during all the decoder and engine handling while running all the initial tests. After prying loose part of the decoder shrink wrapping I managed to solder a new wire to the decoder.
Problem #3, the red speaker wire fell off in the processm but it was soon soldered back, but I must admit my spirits were starting to fail...
But in the darkest of hours - success! With the capacitor in place the engin ran like a charm, where it earlier dropped dead every 10 inches.
All is good then you might assume. But no. Problem #4: At this point of triumph the capacitor which was sitting on top of the frame fell off and its legs shortened on the engine frame. Result = burned and destroyed decoder.
I have just ordered a Digitrax DZ125 deocder. The sound adventure is over for this time.