My wife bought an HP C5180 Photosmart printer several years ago. A few months back, it started acting really 'weird'. It claimed all sorts of bogus errors and problems, and I never had any time to look into it. Recently we were cleaning up the house after moving our bedroom upstairs, and I ran across it. I plugged it in, thinking perhaps time had healed all wounds.
I was wrong.
The printer was now in an endless loop of reboots. Not wanting to give up on it quite yet, I looked online for the symptom. "Blown capacitor," several articles said. Intrigued by the opportunity to tear it apart, I grabbed my Torx set and pulled it to pieces. Sure enough, there was a 330uF 10V capacitor with bulges on top and bottom. I honestly didn't think it would be so obvious, but there it was.
The closest component I had was a 470uF 16V capacitor, and since I figured I couldn't break it anymore than it already was, I swapped it out. A solder sucker would have been pretty good to have here, but I had to make do with some braid and some tweezers. I also noticed a whole lot of heat was required, maybe due to lead-free solder being used?
Viola! The printer sprang to life. My wife may have actually been impressed; hard to say. Total cost to repair? $0 and 30 minutes of my time. Downside? The printer refuses to print with 'expired' ink, and the replacement cartridges cost $50. You can buy a brand new Photosmart printer for $100.
As a comparison, our HP LaserJet 4L -- manufactured in 1993 -- is still working like it's brand new.
I bought it on eBay for $30, 10 years ago.
If you're going to try this repair yourself, remove the plastic panel on the side of the printer next to the power, ethernet, and USB jacks. There is a Torx screw in the back, and one accessible by lifting the printer lid. You can get access to the control board by removing the half-dozen or so Torx screws that hold it in place.