I simply bent the heatsink to make contact with the copper-wound transformer (which is insulated). The heatsink is shaped so as to do so, but maybe it is not meant to touch the thing. I think I will ferret out a service manual just to check on your suggestion, since it makes perfect sense.

In response to your whining issues (ha), I had an unstable Duo 280c (capacitor leakage) that had the whine from that area, but I have functional 270c and 280c Duos that are perfectly silent. The 2300c is also silent, but it has some other issues, as we see.

I had a peek at a PB145 logic board the other day. It has no capacitors at all. My Wallstreets also have no cap-capacitors to speak of, excepting the battery charge card. The Duos have lots. This has to be a major failure point in this model; could the whining be related to capacitor failure?