camcorder Drum cleaning

Hello,

Please what's the best method to clean a camcorder heads ( video and sound) embeded in Sony camcorder drum?
I've tried using Q-tip, alcohol and white paper, but the LCD is still blue and no image or sound are out.
I confirm that V/S were working fine juste before a repair periode (10 days), the K7 was in the camcorder for all this periode, the drum was uncovered and the dust maybe introduced in the drum!!!

Thanks in advance for your help.