This is headed in the wrong direction.
Once the drive gets into that bootloop, it takes a hex editor, a TCF expert, connecting the drive to a PC, and luck to even hope that drive will ever boot again. I speak from experience.
Sure, the power supply might have some aging caps that lived their lifetime, and are now no longer providing clean power. But, even if you put a perfectly good power supply in, the drive would still GSOD boot-loop.
KS 57 & 58 are notorious for causing this on pefectly good TiVos, with perfectly good power supplies, and perfectly good drives.
There are threads for this. Unitron should know them. He's been participating in the threads about the magic superheader with "EBBAFEED" being what you want put back into a certain place with a hex editor. That string will be missing.
Running KS 57 or 58 "just because it seems like a good idea" is the worst idea, and the odds of this exact problem happening are more in favor of this result, than tossing a coin.
Sorry. I had to learn this the hard way too (multiple time, even). I never was able to recover from it. I only recently spotted that somebody had found the fix, and it isn't easy, or guaranteed.
So, unitron and friends, please guide this poor soul to the many threads it will take to fix the data corruption on the drive, or to re-image it, then worry about the power supply, once the drive is ready to go in (or back in).