I have one of these Marklin E03 TEE C-Sine locos. Runs very well but has some limits. The decoder is the earlier 6090 type with a DIP switch.

I am "upgrading" this loco because it only has a horn sound, and no available spare function outputs, so I can not add telex. As a result, I have not used the loco very much.

Because it has the dedicated 701.40 decoder, which means I can not change the decoder, I am changing the motor bogie to the "normal" old type motor with a permanent magnet, and that will allow me to use a Loksound V 5 decoder.

So .... I now have a spare C-Sine motor plus motherboard plus loudspeaker etc.

If the C-Sine system in your loco has failed, to the best of my knowledge it is normally unfixable. For a start, how does one tell if the fault is the actual motor, the mother board, or the crappy printed circuit "cable" that connects the motor to the decoder. There is no way to tell except by substitution. And guess what? Surprise surprise, these bits are no longer available from Marklin. Here is your chance !

I am happy to make these bits available to someone, or if you want to send your loco to me (I am in Oz) I can do it for you.

regards
Norm.