For those interested and looking for the conversion kit Tones has mentioned which will convert a troublesome Hitachi EX and whatever John Deeres which they cross to (ie my 790ELC), ebay had a vendor selling the kits! Here is one example; http://www.ebay.com/itm/EX220-3-Hitachi-Excavator-Conversion-Kit-with-English-Installation-Manual-/251979520458?epid=1887866581&hash=item3aab2659ca:g:QSwAAOSwvzRXyVST. A bit pricey but if mine continues to give me grief, it could easily pay for itself quickly in lost production if it works.
"if it works" is the big question. I don't recall hearing from anyone who has installed one to know how they actually work.
conversion kit work but perfomance not as good as electronics....pump is too hot need to replace with viton type o rings