I have and old Xerox DocuColor 4 LP and when power on it shows U3-5 error there is no information on line for this particular error on this model and unfortunately there are no technicians here in Mexico that will service this particular model, can some one help me?
while not overly helpful, I was able to find this from a service manual found online:
Problem:U3-5 error code at power up.Cause:Lack of switched +5 VDC due to a damaged LVPS. note-ROS, MCU as suggested by FIP and Top Cover Interlock Switch (152925) were replaced unsuccessfully.
Might give you a place to start at least.