It sounds like you need a manual that would include the schematic - something the manufacturer could supply or that you would get from Sams or other commercial suppliers. You will need the manufacturer's name and model number, at least, to get the information. Post it here - someone might have one or might be familiar enough with the circuitry to offer some help. I've seen manuals offered for sale on ebay however they are usually for equipment that is popular among hobbyists.