Transformer Woes

[RobertInOntario]

The 7VA (VA = volts times amps) rating is too wimpy for older locomotives. It translates to a maximum of slightly more than 0.5 amps at 12 volts. It certainly won't handle the load of throwing a switch machine (typically 1-2 amps) without choking eventually. The rheostat (the part that controls the speed) is probably cooking under the load of your engine and any lighted cars, and can/will eventually fail. I had an old AHM train set power pack with a similar rating that went down that road. I was able to salvage the power pack by using the AC terminals as a power supply for a transistor walk-around throttle I built. This didn't improve the output rating of the power pack, but did make a nice throttle for my better locomotives.
As I have gotten more experienced, I refuse to put up with locomotives drawing more than 0.6 amps. The mechanism needs tuning or the motor needs new magnets or replacement if the current draw is that high. An ammeter is a great tool for base-lining locomotive performance and tuning mechanisms.
In the meantime, use the Railpower power pack for your older trains. It has a much larger power rating, and MRC built them with sturdier components than the typical train set power pack.
my thoughts, your choices
Fred W

Thanks, Fred. This is really helpful. The LHS who sold me the Athearn one assured me it was one of their better, most reliable transformers! When I first bought it, it did provide a fine range of speed so that my locos could creep along nicely at very slow speeds (both old and new). However, I do seem to have to crank it up more now.

Based on the above, what would be a good transformer for me to use, since I run a mixture of old & new locos on my layouts? Shall I stick with Railpower or are there other/similar ones? The Railpower ones were affordable yet I'm not sure if they're readily available these days.

Also, maybe I should use the Railpower one for the turnout rather than the Athearn one?

Thanks again,
Rob