It may be helpful for you to know that the model number of the power supply is PLS-150.
You can find pictures and further information here:
http://www.marklev.comI doubt that the present Mark Levinson/Harman International company will be of much help. They probably no longer have the parts to repair that power supply, much less a complete supply. I know for a fact that they no longer have replacements for the potted phono amplifier and line amplifier modules which are in the preamplifier section of the ML1, and replacements for those modules are essentially impossible to find without buying a complete ML1 (which are highly collectible and go for $2K to $4K on eBay).
And speaking of the amplifier modules, which understandably do tend to develop problems after their 3 decades or so of existence, I would suggest not investing too much money in a power supply given that you have no way of knowing if the preamplifier section itself is working.
You may want to consider the possibility of selling it as is, and using the likely substantial amount of money it would bring to buy something newer.
Best of luck with it!
-- Al