A few transformer questions

First off, the TW is not really a 175W transformer as far as rail power is concerned.  It's an oddball with dual windings, so the variable section is only rated at about half the output power.  Also, the old PW transformers were rated by input power, not output power, so figure about 75% of the rated power available at the terminals of any PW transformer.

The ZW and KW connect the U terminal to the outside rails, the 1033-1034 connect the U terminal to the center rail.  Truthfully, I forget which way the TW connects.  I've never had an LW, so I don't know for sure which way that one connects either.

As far as protection, you need a fast acting circuit breaker or fuse in each output connection from and old PW transformer.  I also recommend a TVS protection diode for any track outputs if you use locomotives with any electronics, even conventional.

The TW has two completely separate 90 watt(input) cores, it's like having a 1033 to run just trains and another 1033 just for accessories, without taking away from train performance.  The "A" posts are clearly marked as common, as is the convention with Lionel postwar single-train transformers.  Same with the LW.

The RW could be used with "A" or "D" as common, but "U" is definitely for the center rail power - the wiper(throttle), direction, and whistle are all on the "U" circuit.

The Williams transformer has better circuitry for whistle and bell activation, and in practice will be about as powerful as a the RW or LW.

I know this is pretty simple in the solution realm, I just find it works well for me...I have added a fast blow 7 amp glass automotive fuse to all my center rail feeds from the transformers.  I use a simple auto fuse holder and I use two PW ZWs.

I know this is low tech, it just works....

Some useful info here:

http://www.jwtrains.com/Tech%20Tip_6.htm

Transformer-Common Post-Variable Post

1033        A          U

1044        A          U

KW          U          A,B

LW          A          U

RW          U          A,B

SW          U          A,D

TW          A          U

V             U          A,B,C,D

VW          U          A,B,C,D

Z             U          A,B,C,D

ZW          U          A,B,C,D

Looks like if there is one throttle, post U is variable [hot] post.

If there is more than one throttle U is common post.

JW is wrong on this one.  The RW can be used with "A" or "D" as common, but "U" is definitely for the center rail power - the wiper(throttle), direction, and whistle are all on the "U" circuit.  If "U" is used for common with other transformers, it will power up OK,  but the direction button and whistle control won't work.