TMCC Command Base not working

Are you powering up the base first?

There can be a delay with the signal getting to the track after the power is already there.

Is the wall plug for the base plugged directly into the wall or a powerstrip?

Some powerstrips have been known to degrade the signal.

One side of the Tmcc/legacy signal is broadcast from the ground wiring in the walls of the room the layout is in via the ground lug on the base wall plug.

I'd first test the base on a test track on the bench.  It sounds like no TMCC signal.  Did this happen suddenly or is this a base you acquired that never functioned?

Thanks guys. This is a unit I'm testing for a friend- it was recently purchased and he has not been able to get it to work. I can swap it out with my working unit and the results are the same (lights up but locos immediately  start up in conventional), so that rules out the power supply and connection to layout.

Thanks.

Sounds like a track signal issue.  It could simply be out of tune, that happens to the old TMCC BASE1 as it has a coil to determine the frequency.  It could also be the signal is simply not there, the only way to know is to measure the signal.  Here's a rig that the late Dale M. came up with, you could compare your base to his and see if you have a big difference.  This is done with the base not connected to anything.  Since yours works, if he has a similar reading, I'd think the base is out of tune.

But neither base works, the working one and the mystery one. Maybe something with the wiring. U terminal goes to outside rail?

Thanks John. With my setup I get 4.1 vdc, and 3.6 vdc on the inop unit.

Do you have a procedure for tuning?

This is from the late Dale Manquen's Trainfacts website.

If the frequency tuning of the Base oscillator shifts away from the nominal value, the receivers in the locomotives may have a reduced sensitivity. Re-tuning L8 is a bit risky, but sometimes this is necessary. Using the least sensitive locomotive as a reference, press the horn/whistle button on the CAB-1. Use a plastic screwdriver to adjust L8 back and forth until you determine the extremes of the adjustment range that will activate the horn/whistle. Now adjust L8 to the middle of this adjustment range. Check all you other locomotives. (You could have just one bad locomotive and a good Base!)

The site is still up, so here's the whole page on the command base: Lionel TMCC Command Base 7/29/11

I have no idea how much longer the site will be active as sooner or later the domain name will expire.  Looks like next year...

Registrar Expiration Date: 2020-07-21

The "U" terminal on the TMCC command base is made of Aluminum and works loose very easily. Crimp a ring terminal to the wire going from the TMCC command base to the track. Put the ring terminal on the TMCC command base "U" terminal. Take the wire directly to the track and connect it to the outside rail.

If he just tested the command base totally disconnected from the layout, it's hard to imagine that the wire from the U terminal is loose.

Thanks for link John. Lots of good info there. Unfortunately I still get nothing across the range of adjustment on L8. It sure acts like there is no output signal at all...

There may be another failure, hard to say.  My next step would probably be to 'scope the output to see if it's in the proper frequency range.  It may be out in left field, that would explain why it doesn't respond.