Murphy's Law of Post-repair Reassembly

"A device that you're repairing will operate **absolutely perfectly** while you have it taken apart to work on it, but then when you get it all put back together and have all the cabinet-screws re-inserted, THAT'S when the device will decide not to work again."

To lessen the chance of getting "bitten" by Murphy's Law of Post-repair Reassembly, one should double-check everything on a refurbished device before putting it back together again.