I have one of these decoders installed in my Ixion Coffee Pot.
The first decoder was dead on arrival but was replaced by Soundtrax, I installed the second one and programmed it ok.
It runs fairly well except for one thing.
Every so often the loco stops for a second or two then restarts, no matter which speed step I have it set to it takes off like a scalded cat, I then have to throttle it back to the required speed.
If I reset the loco either by turning off the power or removing it from the track it behaves itself again until the next stop.
I am not sure if these stops are caused by dirty track or a fault in the decoder.
I am using the NCE Powercab.
I had a similar issue with that soundtrax decoder in a Bachmann Gas mechanical. Solved the problem as it was thought that there was in fact two issues.
1/ That decoder gets very hot so made sure it had plenty of space around it (well as much as you can get) added a heat sink out of a piece of aluminum and drilled holes in the body of the loco to let more air around it.
2/ We added the capacitor to the circuit ( had been told by some guy that it was not needed) that was wrong.
Now works like a charm. There are some photo's way back in my post that might be usefull.
Trust this is of some help.
Tried the capacitor in the circuit but it makes no difference.
I should mention that the decoder is attached to a large piece of thick brass plate mounted in the roof space of the coffee pot passenger carriage, I have run the CP with the roof off and the decoder stays cool to the touch.
All my other locos run fine on the track without issues, these range from a 4 6 0 to a small diesel switcher.
No matter which speed setting I run the CP on it stops after a few seconds, then restarts itself but at twice the speed, when it stops again it will restart at four times the speed.
If I put it into reverse from this situation the loco once more runs at the set speed until it stops of its own accord then goes into its speed doubling act.
I know the symptoms of dirty track the stopped loco usually requires a small push to get it going again.
I am coming to the conclusion that this replacement decoder is also faulty.
Your comment re the capacitor set my mind off on another track (excuse the pun) and after further investigation found that I was routing power to the carriage lighting through the decoder.
Normally this wouldnt be a problem but with the low rating on the 750 it must have been enough to cause an overload trip which of course reset itself fairly quickly.
I disconnected the cabin lights and away she went, hopefully no further issues.
I ran the loco for twenty minutes without a hitch.
Many thanks for your help.