I bought a broken PS2 on eBay hoping for it to be an easy fix, the listing only mentioned that the motherboard was defective, so I figured all I had to do was take it apart and replace the motherboard with the spare that I saved from another PS2 that got cosmetically damaged from an accident a long time ago. Turned out it also had an issue where the disc wouldn't spin when inserted, which meant the spindle motor was seized. I took it apart again to replace the spindle only to find out the spare I had has a puncture on the ribbon cable, which is soldered directly to the spindle motor circuit board. I tried to desolder the cable from the dead motor, but ended up destroying it in the process. I had to order a new spindle motor for the disc drive, which set me back another $28 with shipping and tax included (the console itself was around $45 including shipping and tax).
It's not a huge deal since I already have a working PS2. I just thought it would be fun to get a broken one to try to bring back to life using my spare motherboard, but it turned out to be more work than expected.