TMCC Big Boy not responding to CAB1

Your symptoms suggest a serial data failure going to the tender.  First stop would be to check the IR sender on the locomotive.  Point your digital camera or phone camera at it and power up the locomotive.  If you see a dull purple glow, the IR sender is functional, if not, it's broke.

You can also take another Lionel TMCC wireless tether tender and try it on this locomotive.  If that functions normally, it's the tender that has the problem.  If it doesn't function, then it's the locomotive that has the problem.

Great ideas- I do have a tmcc tender from my AC-9- forgive my ignorance- with my camera- do I turn it on in picture mode or video mode- also new strange thing- the horn goes on when it passes over any switch- also the smoke unit works but no chuffing. Thanks again-Rolf

John, I put my SP AC-9 tender on and it worked perfectly- have to figure out what is wrong with the tender

Well, time to peek in side the tender.  First off, check the tether sensor under the heatshrink.  I've had several with a broken wire on the sensor, no serial data starts up in conventional mode.

will do John- do you have any idea why, with the bad tender, the horn blows when it rides over any switch- strange-thanks again-Rolf

That's just an artifact of it getting a momentary break in power and seeing what looks like a horn signal.  it's not uncommon, especially if the wheels, pickups, or track is dirty.

Thanks again John for all your help- Rolf

SUCCESS!- you were right- one of the wires coming out of the wireless tether, was only half way in a 3 pin connector on the circuit board- I used a pair of tweezers and snapped the plug back in- everything now works like a charm- thanks very much-Rolf

Love the easy ones.   Glad it was a cheap fix.

Maybe the problem and fix I experienced will help others who have similar Railsound problems- thanks again John-Rolf