John Deere 5075E will not start

[geojr7793]

I have a John Deere 5075E that will not start. New battery, new negative cable, all contacts cleaned, starter has been checked out as good, new ignition switch. When you engage the starter switch at first position console lights up and starter beep occurs. When you engage the starter switch to the start position you get a click and a very brief surge to starter solenoid/motor and all goes completely dead. When I disconnect and re-connect the battery the tractor will do exactly the same thing. AI suggest a replaceable diode is the problem (Part #LVU804171). Has anyone had this problem or know where this diode is located. Thank you