Now I've swapped the Smooth chip from a working drive to the Tonka et voila - the core voltage is back. But it still identifies itself as Galaxy and then tells me stuff I've not seen before:

Reset
8192k x 16 DRAM
GALAXY - 1_Disk S-7A 07-10-07_15:34

Buzz HM SFI
!
(P)SATA Reset
carve writes(H)SATA Reset
carve writes

What the hell is it writing there?
Has the customer swapped the boards, or is it normal for a Tonka to identify as Galaxy?
What about the writing stuff?

Whatever this messages means, I just copied the full 55 Gigabytes of customer data from this drive. I suspect bearing problems as the initial cause for the Smooth failing (increased motor current), because the drive got very hot, 70 deg C on the base after one hour in free air.

Compare the data codes on the chips against the date code on the label.

Its close enough to say the board is original, and as the data copied without any problems or errors, I think it was the original PCB.