If you look at the left hand side of the toner cartridge, you should see a metal shaft about 10mm in diameter and 5mm long. As you push the toner cartridge into the printer, this metal shaft slides under a spring loaded metal contact.
The earth contact is L shaped and measures about 40mm x 20mm with a kink in it's short side. If this contact is resting against the white plastic block on the side frame, it has come out of place.
To replace the contact, use a metal hook, or something similar, and pull it away from the white plastic block. Swing it upwards so that it is upright and fit it into the slot. It should then slide down the slot until it reaches the end. When in it's correct position, it sits at an angle of about 45 degrees.
If it's fitted correctly, the metal shaft on the toner cartridge should slide under it. The print quality should now be normal.
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