I was googling the other day and found this post. I dragged my 600xl(64k) & 130xe out of the closet(15 plus years) last week and was surprise that both worked.
Now the floppy drives were another critical-care case. The first drive TRAK AT-D2 plugged in, turned on, spun and displayed the 00 track. Oh where is that SIO cable, dig some more and ah-ha, got it. I sat back down and humm, the drive lights are off. oh well, turn it back on, power cable plug must be oxidized. Plugged in the SIO cable on computer and drive - lights off again. Okay, this does it, my front panel membrane is de-glued from the case, I will pinch between thumb and finger. It will not stay on unless you hold the contacts closed all the time. And like-wise rattlesnake sounds from the power relay in the back. Tried transformer #2 - same problem.
l gave up moved onto my XF551. It turns on, looks good, where are thoose disks. Disk 1 - spins - beep - spins stalls - spins again - stalls - ... boot error etc, etc, etc. !@#$.
Before I dragged out my old Atari 8-bit machines, i was watching on YouTube about fixing old Commadore computers 2-3 hours fixing old pets, Vic-20s, C64s, etc. and hence the crazy idea to drag out the old Atari's I owned. But during the videoes - power supply issues are common in Commadore machines - aka old Caps - leaks, or dried out electrolyte, or puddling (causing shorts) - Commadore went cheap on overvoltage ceilings eg. 6.3v-9.0v for 5.0v usage. Atari used 16v-35v caps which are more abuse tollerent and as noted in the video gives more life to the device. However, power supplies are another issue. Power caps are big and are not cheap compared to other components. Look on the internet about 70-80s power amps with true 200-300 RMS Watts - Re-capping is common
Now what could be wrong with both drives? Power suppy problems? Maybe.
Need to bypass the internal power supply +5v & +12v - hey why not piggy back onto a new computers peripherals molax cable.
Get one of the peripheral y-splitters or double wire the drive and back to the PCB the +5v, +12v, and Gnd.
Turn on the computer check +5Vs between 4.95v-5.05v and +12Vs between 11.90v-12.10v - 1% tolerence. There are many examples on the internet how to use modern day power supplies. You may need to unplug the PCB to get a clean boot of the controller as I was using jumpers and the TRAK was reading out wierd codes.
Short to say XP551 still doing its disk spin shuffle but Trak AT-D2 has been loading old games with occasional bad sectors. Amazed that disks are still working after 25 plus years. The power supply in the TRAKs has 3 large Caps +12.1V, +12.4V and 24.6V(voltage doubler curcuit) rated @ 35V 4700Mfd and 1 small cap next to the CPU - 10Mfd @ 6.3v. If the drive works then there is enough guts left in this one. All others are monolithic caps where a hammer or acid bath is the likely demise of these caps - hence likely never will die in your lifetime. 2 large power regulator 7805 & 7812 what I remember the heatsinks used to get hot enough to burn you. They need 3-5v drop across input and output, so, 12v -> (24.6 - 12.0) x 1A = 12.6Watts of heat and 5v -> (12.25 - 5.0) x 1A = 7.25Watts of heat but rated at 1.5A max each. Plus 2 diodes - working and if not then large caps would not all charge to a reasonable voltages. 9Vac x 1.4 (rms calculation of sinusoidal wave shapes) = 12.6v, and diodes drop 0.4v-0.7v explaining the 12ish volts. Plus 1 rectifer bridge - working as previous noted caps.
Two/Three options - 1) replace with new PC power supply, 2) replace all large Caps (must find 35V 4700Mfd in proper can size to fit the PCB board and case) assume bad, 3) remove caps and test with Digital Multi-Meter with Capacitor testing feature for high values. (or like-wise test equipment) and replace bad spec caps.
Unlike cause regulators cutting out under load due to age? Would need to investigate if ever happens.
Or final option recommended by Dragonstomper - pay some one to fix.
Good luck on what you try.