A friend gave me his Bachmann S4 saying he could never get it to run right. Very jerky performance and stalls.  I checked it out and it seems that even though the front trucks are picking up power from the rails, that power is not being processed by the decoder.  I notice there are a pair of wires that go to the decoder from each of the trucks.  The little copper wipers are picking up power off the wheels and power is going to the decoder, I have confirmed that.  Seems to me the decoder is defective and not processing the power from the front trucks.

My questions.  One, am i missing something in my trouble shooting?  Two, if the decoded is bad, are replacement decoders available and is it cost effective to do so or just replace the loco.

Thank you CV62