Excavator hitachi ex120-5 bucket and boom not function

Hi, I have hitachi ex120-5 excavator, since a week ago we try to solve the problem with no success, after the engine is start the bucket and the boom will work only around a minutes then it will began to slow before completely didnt function. Swing and track work fine. We already service the control valve (bucket flow control valve and boom anti-drif valve), but the problem still. Thank you for the future help from this forum. Sorry, for my broken English.