OK, the Z 1K and Z 750 are bricks with an output of 21 vac in one MTH manual I read. When you add the Z controller, the output becomes a shark tooth output. Apparently the new MTH engines are fine with this, not so the much earlier ones. The Lionel would be fine with that except Lionel says the max voltage that can be used is 19 VAC. The possible issue with the Z 750 is that the peak voltage even when you use a controller is still based on the 21 VAC and could be too much for the Lionel engine. So use of the Z controller may not be effective in satisfying the Lionel limit.
That's why I was asking the question about the Z transformers. As to what the happened to the Z transformer and why is still in question unless MJR unpluged the transformer and it did reset, but I have not seen his answer to that suggestion. Considering the voltage limit and the higher power requirement for two engines, the safest, capable transformer would be the Lionel CW 80 or even better the GW 180. I suspect the Z 750 would probably be ok since we are not really privy to what Lionel means by the 19 VAC limit (does peak matter or just RMS). If it were mine, I'd just get the GW180.
