The drive would power up but not stay on once the disk was being accessed and it would reset. The problem was obvious bad power supply.
Back to Google I go and I found the wonderful blog World of Jani with what I needed.
http://blog.worldofjani.com/?p=2131
I wasn't too keen on the original bare power supply or trying to fix it. I wasn't able to get that model mentioned in Jani's blog either. In the end I picked up another caged Mean Well power supply from RS components and set to work.
STOP . . . These voltages will, KILL YOU . . . STOP
I don't recommend doing this at all, mains voltage is really dangerous.
Get someone qualified to do it for you.
This is the unit I ended up ordering and installing :
https://au.rs-online.com/web/p/embedded-switch-mode-power-supplies-smps/6447073/?sra=pstk
Now I have a beautifully functional 1571.