Many Thanks for the input.
We opened it up today and spotted a small and obviously blown surface-mount capacitor, close to the AC input from the transformer. There appears to be an in-line fuse in one output lead from the transformer, covered with shrink-wrap. The transformer had output through the fuse to the board and the cooling fan operated. I suspect the blown capacitor is just the visible manifestation of a problem in something else.
Solution: we will look for a replacement transformer with a higher rating.
One good thing about a blown CW-40: it would be very easy to convert it to a fixed voltage supply. Just cut out the circuit board and run the transformer output directly to the output terminals. The hardest part is, you need a special triangular screwdriver bit to open the case.