A train repair friend (who does mostly non-electronic work) was given a non-working CW-40 transformer to try to repair. He had to grind himself a triangular screwdriver bit to open the case. He tells me it has a circuit board inside with something obviously blown. I haven't seen it yet myself. It has whistle, bell and direction buttons, basically a junior version of the CW-80.
Now I know a 40-watt transformer is a marginal-output train-set item and I suspect it's not repairable, but if anyone has useful info or suggestions from personal experience, they would be appreciated. Thanks!