I have an EC500-50 forklift that has not been maintained well. I am in the process of rebuilding and repairing it. The problem i am writing about it that the throttle peddle currently does not provide smooth control of the lift. It is quite jerky and hard to feather or vary speed. Especially when trying to move slowly. The peddle has two micro switches, one engaged at full speed and the other at stop plus a rheostat/potentiometer. I do not have any schematics for this lift nor have I been able to find any making it very difficult to perform diagnostics on this drive.
Common sense tells me this thing must have some sort of chopper drive to control the average current to the traction motor but I don't see much in the way of electronics at all. Only electro mechanical items such as large relays and fuses inside the back cover. In my experience one can normally hear the whine of a chopper drive but this lift is quiet except for the hydraulic pump and I am stumped as to where I should start.
The serial number is E355 306 2300 if that helps