We have a PowePac 300 giving e8

I am trying to find out any information on a PowePac 300. when I set a voltage it will set but when I turn the unit to run I get zero volts out and then e8 pops up in the display. the only information I have found is that e8 means there is a problem with the unit not helpful. if anyone has a schematic or service information or service manual it would really help.