First off, make sure the printer is NOT using the EPSON drivers. Too long using the TM88 driver will cause the printer head to burn up.
Past that, you can open up the DIP Switch tab on the bottom of the printer (in the bottomo left). ON the lower Bank of switches, set switch #5 DOWN, and switch #6 UP (most dark) and then dump the printer. If that is too dark, try switch #5 UP and switch #6 DOWN.