Speaking of heat sink heat, I had to replace the transformer in a Mk1 this past week. But the original is a custom unit rated 8v secondaries, 2 x 25VA and not available. I chose an off the shelf 6V rated out 2 x 25VA unit and tg it's working fine, with less heat across the linear regs too of course. It's actually delivering about 7.4V AC V out in mine. The original toroid has a band shield, and there was room in there to wrap a band shield around the new one. I went with this one: Triad- VPT12_4170
TK