TMCC Base 1 power supply

Here is a replacement 12 volt AC transformer that will work.  It has the necessary ground plug for the TMCC earth ground signal. The annotations in the image below, show where the barrel connections attach.

If you are using the Base1 in conjunction with the Leagacy Base (via the Y cable), you don't need a TMCC signal to the track & wiring ground on the Base1.  The Legacy Base provides the TMCC signal.  A 2-prong  wall wart with the right-sized barrel, voltage, and amp output will work.

OK, I just purchased the 12VAC transformer PWS-1240 on Amazon. So I simply have to make a cable up with the correct size barrel connector and observe your suggested wiring, right?

(tip to the left most screw terminal, and the sleeve to EITHER one of the remaining terminals, or BOTH?? Jumpered together?)

If I have the 3 prong transformer plugged into a surge strip, is that going to defeat the necessary earth grounding??? In other words, do I HAVE to plug the transformer DIRECTLY into the wall socket?

Last question- Am I damaging the old TMCC base by using my Legacy 8 VAC 300 ma as a power source?   The Base 1 calls for 12VAC, 100ma. My plans are to save some wear and tear on my newly acquired RARE and now extinct  Legacy 990 system and use the TMCC Cab1 and Base1 most of the time exclusively- NOT with (or through) the Legacy, if that makes any sense. Besides, right now I only own ONE Legacy engine so far.

@jpepe3691 posted:

OK, I just purchased the 12VAC transformer PWS-1240 on Amazon. So I simply have to make a cable up with the correct size barrel connector and observe your suggested wiring, right?

Correct.

@jpepe3691 posted:

(tip to the left most screw terminal, and the sleeve to EITHER one of the remaining terminals, or BOTH?? Jumpered together?)

If only using the TMCC Base 1 by itself (without the Base 2), then you need to connect the barrel connector's Sleeve to both transformer terminals as pictured above, jumpered together to provide the TMCC signal to earth ground, plus the AC common power connection from the wall transformer to the Base 1.

@jpepe3691 posted:

If I have the 3 prong transformer plugged into a surge strip, is that going to defeat the necessary earth grounding??? In other words, do I HAVE to plug the transformer DIRECTLY into the wall socket?

It is generally recommended to connect the Base transformer directly to a wall outlet, not through a surge protector because some surge protectors don't have ground continuity from input to output.  But, if you can verify that the surge protector you intend to use has continuity from the ground pin input to output, then it's ok to use the surge protector, this is what I do.  Of course to check said ground throughput continuity, make sure to unplug the surge protector from the wall first, for safety.

@jpepe3691 posted:

Last question- Am I damaging the old TMCC base by using my Legacy 8 VAC 300 ma as a power source?

Probably not.

OK, thanks for the clarification. I'll check that surge protector to make sure it is passing the ground through (obviously not plugged into the wall). And, yes, for the time being, I'll be using the TMCC base 1 by itself for the most part. Right now I just successfully hooked up a TPC400 to the BASE1, and it works just fine in conventional and command mode. Of course, I'm temporarily using the Legacy's 8 VAC 300ma transformer.

Thanks for all the help! This forum is a life saver!

OK, sorry to go back to this, but I must be DENSE.  I just don't want to risk damaging  an increasingly hard to find TMCC system. I just received the PWS-1240 12VAC transformer pictured above. The 3 terminals are clearly marked, from left to right, looking from the back, AC, GND, and AC respectively . If I measure the AC voltage between the LEFT AC terminal and the GND I get 4.3 VAC.   Measuring between GND and the RIGHT AC terminal I get 7.1VAC.  Measuring between the two outer AC terminals I get 13.7VAC.  And this is connecting the transformer DIRECTLY to the wall, via a 3 prong extension cord.

What I don't quite understand is why I wouldn't be risking SHORTING OUT this transformer by JUMPERING the center GND terminal and the right most AC terminal, and wiring that up to the sleeve of my barrel connector??

And the left AC terminal goes to the tip, correct?

Do I have this right?    Or did I misinterpret something here. Again, forgive my ignorance, but is this the same as connecting a neutral and earth ground together in house wiring?

You are measuring stray capacitance.  Try putting a 1K resistor across the the right hand two terminals and you'll see that you suddenly have no voltage.

I suppose you could say it's similar to the connection between ground and neutral in house wiring, but remember that the secondary of the transformer is totally isolated from the primary, so we're not doing anything dangerous.  As a point of fact, we're doing EXACTLY what is done in the TMCC and Legacy bricks for their command bases.

OK, just wanted to be sure. Meanwhile, I looked up your guidance with "Manitou" from a previous post, and you verified exactly the same wiring of a 12VAC 3 prong transformer he had, so all is well. I'm going to proceed to wire up my cable accordingly. Thanks AGAIN  for your help!

Just an update- Wired up the new transformer exactly as described, and VOILA! It all works!

Thanks again