Perform hard reset for your printer. Following are main steps for hard reset.For complete setup go to Canon iPF750 Manual. (1) Turn ON the printer. (2) Press and Hold the “Reset button” on the printer. (3) While pressing the “Reset button“, press and hold the “Color Start” button. (4) Wait for 5 seconds. (5) Release the “Color Start” button, and then release the “Reset Button“. (6) Wait until the printer starts to configure itself. ...

The most useful solution to fix this error is to perform factory reset of your device. For steps of factory rsest check Canon iP4850 Manual. If factory reset improves nothing then contact with technical support person.

Check the complete pictorial view in Dell Venue 8 Pro Manual and get enough knowledge about how to recognize issue in USB port and fix it.

This happens because when we change lens then some dust particles come inside of camera. To prevent spots on images you have to clean image sensor of camera. You can clean your camera in 2 ways that is auto cleaning of camera and clean your camera using blower. Check Sony RX100 Manual for detailed view of these both methods.