If you have a Time Capsule, you won’t have escaped the news that they tend to die sooner than they should. The Time Capsule Memorial Register will have been on your mind, especially if you’ve read the news reports (see ‘Apple finally admits problems with Time Capsule and offers replacement’ in The Guardian, for example). All the more worrying if you use the thing for a Time Machine backup.
I sent mine to Chris Fackrell, who tested and repaired the power supply, then punched a hole on the baseplate to enable ventilation. Well, ‘punched a hole’ is what I would have done; what Chris did is indistinguishable from OEM work, save for the use of a metal mesh (which does look better than the cutouts in plastic Apple would have used, if they had designed the thing with adequate ventilation). He also replaced the hard drive, so I got a hefty upgrade in capacity.
The cost of doing this was less than the cost of a new Time Capsule, which would be in risk of failing itself anyway. And much less that the cost of a new Base Station and a NAS, which is what the Time Capsule is in my setup.
If you’ve got one, check it out. My warning signs were overheating of the case, and brown marks on the baseplate.