New Temporary Layout - Power requirements

I'd suggest avoiding buying the 72W DC power supply, unless it happens to come with a set you want anyway. It won't work properly with ~90% of available O Gauge trains and accessories (including older crossing gates).  LionChief being one of these exceptions.

With additional circuit protection (either fast blow fuses or instantaneous breakers) and TVS diodes, there are lots of great postwar transformers out there with plenty of power available for two or more trains with all the bells and whistles and lights and smoke.  If you don't want to reconnect all the external circuit protections every time you set-up a layout, you could build a control board or box with terminal strips that connect the extra circuit protections to your transformer(s) and track.

A few tips: Remove the DC supply from consideration. There is over a century of tradition with AC on the 3 rails and just about anything* ever made will operate on AC. The same is not true of DC - it can actually be destructive to products. As for the 4090, CW-80, or any transformer, use of strategic TVS diodes and external breakers is a must. Operating multiple trains on the small power supplies is not always going to be feasible as it is easy to require more current than they can provide. Additionally, these small transformers only have a single throttle output, so no distinct block/train control. You can either add to your 4090 and build a bank of small transformers linked together in a common ground wiring scheme for multiple throttles and capacity, or get a serviced KW or ZW that have multiple variable throttle outputs and adequate capacity. These KW and ZW models have really fallen to a sweet price point ($100-150 fully serviced) that makes them a great bang for the buck. You can also go new with something like a GW-180, but that only has the single variable throttle output.

Not a definitive answer, but much to consider and refine and keep the conversation going here. Glad to help navigate one through as they see fit.

@SteveH@bmoran4 Thank you for your informative responses.

To be honest I'm not sure how much I would run my older engines once I get newer items. I may want to run them occasionally which I know would require the transformer.  I only have two of them.  That's why I was considering just going DC for any new LC/LC+ items I get and if I wanted to run an old engine then disconnect that and plug in the ac terminal track.  Not very efficient I know. It's such a small area I don't have a problem doing so.

Taking my older conventional trains out of the equation if I was just going to set up track and have some LC/LC+ trains would I be ok with the 72 DC or is there a better DC product?  I wouldn't be running more than two LC trains at a time.

My thought of operating multiple trains was only for the newer engines.  So if I used the transformer I would power the track and use the remote/s.  I'll have to look more into that TVS.   I was under the impression the newer CW transformers had more robust protection. I watched a few videos of Lionel demonstrating the use of transformer with LC products and surprised they didn't mention anything about possible issues.

It's unclear if you realize the LC, LC+ and LC 2.0 engines will run on DC or AC.  If you're concerned about protecting their electronics but want to continue using your 4090 (or any other postwar type transformer), then maybe consider adding some Fast Acting external Breakers such as the Airpax Instant Breakers (or fast blow fuses) plus TVS diodes.  Like I mentioned before, they could all be mounted in a box with leads going to your transformer(s) and track.

As stated before, I don't find DC has any place on a 3 rail O gauge setup. Stick with what has worked for over a century and works with everything in current and foreseeable manufacture - AC. The only advantage I see to the less capable DC supplies with the LionChief family of sets is the reduced costs of manufacture, reduced size, reduced weight, and shipping for the RTR sets.

Thank you both for your information! Very helpful.

@SteveH Yes, I was aware they could run on AC as well. I was just trying to come up with a solution where I wouldn't have to add the breakers or TVS.  It's something I'll have to look into.

@Zildjianmeister68 posted:

I was just trying to come up with a solution where I wouldn't have to add the breakers or TVS.

Again, adopting best practices:

@bmoran4 posted:

As for the 4090, CW-80, or any transformer, use of strategic TVS diodes and external breakers is a must.

Can you get buy without external breakers and TVS diodes - some do, but why take the risk? It is extremely cost effective insurance to utilize proper power distribution and realize that no transformer can have optimal power protection for every conceivable distribution setup. Then, consider Lionel's spotty availability on some of the replacement circuit boards for the modern products! It becomes maddening when you see fellow hobbyist cut corners or tune out because it is all electro-babble nonsense.

Even if you were to use a the DC power pack, it doesn't have fast enough circuit protection (or TVS) to protect modern locomotives' electronics from damage that can occur due to the Transient Voltage Spikes that are generated during derailments.

This is excellent information. Thank you both.  I'll look into additional circuit protection and TVS.  Better safe than sorry.