Can I Wire It Up Like This? [UPDATED] July 6, 2022

There is a caveat note in the SER2 manual. https://www.lionelsupport.com/...50SER2UsersGuide.pdf

On page 12 of the manual this caveat.

Since you are not using the screw terminal input- example your AMC log loader (I have one of those too) is a receive only device, and therefor not sending data into the SER2 towards the Legacy base, so then you can use the 9 pin serial port AND the screw terminals at the same time.

Just to be clear, a difference since Lionel did some naming. Yes, you have an AMC/ARC log loader. Yes, the separate function module Action Recorder Module has a different function. http://www.lionel.com/products...troller-arc-6-14181/

Wha I'm saying is, yes, you have the AMC/ARC log loader, but it's really more of the Accessory Motor Controller module than the Action Recorder Module. The difference is the ARC is a device that had sensor inputs that then the firmware sends your prerecorded TMCC serial data commands down the rest of the serial bus when a sensor input is triggered. So the ARC box is a true TX/RX bi-directional box. The AMC/ARC log loader  (and the crane is similar) the ARC portion is just it playing back it's own sequence for the function of the log loader motor controls, not sending it back up the serial bus to other devices. It has no sensor inputs like the true ARC module.

I didn't name these boxes and devices, nor did I write the manuals, but reviewing you diagram I didn't want to you misunderstand the ARC part specifically in the name of the AMC/ARC log loader.

Again, per the manual of the AMC/ARC log loader, you are only connecting it 2 wires on the serial data interface, and therefor since the caveat note specifies this state in the SER2 manual, you are supposed to be able to use a single SER2 in your setup with the 9 pin SER going to your TIU cable.

https://www.lionelsupport.com/...ents/72-4115-250.pdf

Page 6 of that manual for the log loader:

You are only connecting the 2 wires, COM and DAT

Back to this picture of SER2 COM and DAT bu not "INP" for input.

Again, just saying, the fundamental difference, you technically have an AMC with limited internal ARC function.

VS, the actual ARC box, which is a different animal.

@Vernon Barry - I appreciate all the helpful information.

I've updated my wiring diagram and think I've got it right.

Please check it over and let me know if anything is incorrect.

Thanks!

I do not think you can use the Legacy serial Y cable as you have shown.

To properly connect to the TIU you need a 50-1032 MTH supplied cable.

https://mthtrains.com/50-1032

Notice this cable has a little electronic box in the middle that does some level conditioning and translation

The Y cable that came with the Legacy base is so you can attach an old grey CAB base to use the old grey remotes with your legacy base.

Again, based on what you posted, you intended to use this cable as suppled with your Legacy 990 set to connect between the TIU and the SER2 in you diagram and that is not the intended purpose of that cable.

That's why the ends are specifically labeled. One goes to the legacy base, one goes to the old grey CAB base, the 3rd is so you can still have a serial port off the Legacy base to connect other devices.

The little square box on this cable is a choke to reduce transmitted EMI/RFI for FCC compliance, it's not doing level translation like the 50-1032 MTH cable.

Again, MTH calls out their specific cable for 50-1032 between the TIU and the SER2.

@Vernon Barry - You are correct; my bad!

Had the right wiring; just the wrong text.

This should be correct - I hope!