MTH Z-1000 with Legacy 990

First off, I'd stop listening to that "Lionel/MTH authorized repair person".  There's nothing wrong with the ZW-C, and it'll do no more damage to your engines than the Z-1000.  The ZW-C with 180W bricks is not a bad choice, but the one correct comment he made is that there is no parts for them anymore.  That's also true of the MTH Z-4000, but it's still a good transformer, just one that suffers from long term support.

The reason that Lionel doesn't recommend the electronically controlled transformer with the PowerMaster is that it also produces a chopped waveform, but it assumes it's getting a pure sine wave as an input.  It's logic gets all confused if it's also getting a chopped waveform.  However, this has nothing to do with the ZW-C or Z-1000, it's a caution for any chopped wave output transformer.  If the transformer is set at full throttle, as it normally would be with the PowerMaster, it'll work fine as you get close to a pure sine wave at full power.

If you're looking at the choice between the ZW-C and the Z-1000, I'd trust the ZW-C circuit protection before the Z-1000.  If the ZW-C is using the 180 watt Lionel bricks, that's even better, they have an excellent circuit breaker circuit.

Yes, the ZW-C came with two 180 watt bricks. But you didn’t answer my most important question: can using the ZW-C damage the circuit boards of either locomotive? If so, no way I will use it. Otherwise, what issues could this “confusion” show up in running and in the function of the Legacy Railsounds and MTH PS2 sounds? Lastly, if parts are no longer available for the ZW-C nor the Z-4000, and if I buy yet another transformer, what transformer(s) would you recommend? Thank you.

Actually, I thought I did answer that question, but here is a more succinct answer.

Any time you apply power to an electronic device, there's a "chance" that you can damage boards.  Obviously, with a properly operating device and a power source that doesn't exceed it's ratings, that chance is very minimal.  There is no reason on the earth to believe that it's more like ZW-C will damage your locomotives then the Z-1000, I can't imagine someone coming up with a rational reason to explain that statement.

The choice of transformer is obviously dependent on your power needs, and your plans for expansion.  Truthfully, unless there's some burning need for more power, I wouldn't rush out and buy any transformer as you already have two that are perfectly satisfactory for running TMCC/Legacy or PS2/PS3.

Okay, thank you. Sorry for all of the questions, but I am a total newbie to digital trains. So are you also saying that the Railsounds and PS2 sounds will work just as they should with no glitches or “confusion” using the ZW-C?

They should work fine.  They surely won't work any better with the Z-1000, which has exactly the same kind of chopped waveform as the ZW-C.