The Youtube video of the SupraDrive power supply emitting the magic smoke has generated a few comments which are very helpful.
Photos of power supply top and bottom below.
DropDeadFrederick suggested that because of other potential issues caused by the capacitor explosion, I may be better off getting a replacement off the shelf power supply like this one. https://www.digikey.com/product-detail/en/xp-power/ECM40UD21/1470-1231-ND/4487612
Even before looking at the power supply the unit was definitely doing some strange things and making strange noises which may indicate the power supply was not in a healthy state. I removed all of the electrolytic capacitors and tested them with an ESR meter and all seemed within spec. Because I did not have new replacements on hand I installed the caps back into the board. That was when I noticed a broken jumper. I soldered this to repair it.
As pointed out by ElectronAsh, this jumper may have been disconnected by design. Disconnect jumper for use with 240V mains power which is what we have in New Zealand. This is likely but it just needs to be confirmed.
I have ordered replacement capacitors so after confirming what should be done with the jumper I will install the new caps and test the power supply fully prior to connecting it to the Syquest drive.
Look out for part 2 of the video.
Thanks for the comments all.