To enter the Service Menu of the 7890/9890 and 7900/9900 printers, you must first turn the printer on normally and make sure it accepts all the refillable cartridges, then turn the printer off. With the printer off, press and hold the Right and Down arrows, along with the Center (hold all 3 buttons at the same time), then push the power button while continuing to hold the 3 buttons until the printer is started up. The LCD screen will look the same as normal startup (should display "Ready"), but when the Menu button is pushed, different options will be available- including more advanced cleaning cycles. This information is all available in the Epson Service Manual, which you can get from www.2manuals.com if you don't already have a copy.
I hope this helps.
Best regards~ Dana