hi, wonder if someone can help with a riso rz370. my problem is that the copier doenst reconize the master roll in the machine, if do have a manual. did the sensor test and it fails. i did replace the master roll and the riso does feed the roll into the riso, all sensor test does work. if i do a test print from the service mode the riso does cut a master on the drum and does feed the paper in to the machine and comes out ok. only light on the riso is the master set light and master light comes and stays on. the display shows "- - - - " instead of a "0". could it be something els?