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Thread: Hitachi EX75UR Fault

  1. #11
    Apprentice joiner
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    Quote Originally Posted by Tractortech View Post
    Now Then..
    I seem to have landed an excavator repair job.. It's a Hitachi EX75UR, imported and repainted orange from what I presume to be the purple colour of the Japanese ones. All the labels on the machine are in Japanese except the fuse box lid which is in English.
    The dipper arm ram loads the engine to retract, however nothing when you try to extend it. The problem I'm sure is electrical in the 'Marccino control', a kind of auto depth control / guidance system. I've found 4 solenoids under the cab, one of which isn't energised, these have the pilot oil running through from the joystick. We now have a machine with the boom stuck right out and some.ground works to do!!
    So, does anyone have any tech publications / info / ideas / experience as to what might be at fault??
    I suspect this machine was built in the 1990s. It has the knuckle boom with 3 sensors mounted at the pivot pins..
    Thanks in advance
    Tt, & co

    it sounds to me like a hose burst valve problem, on the dipper there will be bolted a block, this is supplied with pilot oil to operate the dipper service, in the event of the hose bursting on the lift side it will lock the ram in position until the hose can be replaced, and not cause a safety issue.


    Mick

  2. #12
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    Quote Originally Posted by Mick-the-fitter View Post
    it sounds to me like a hose burst valve problem, on the dipper there will be bolted a block, this is supplied with pilot oil to operate the dipper service, in the event of the hose bursting on the lift side it will lock the ram in position until the hose can be replaced, and not cause a safety issue.


    Mick



    I'm sure the problem is 100% electrical. When it stops working there's absolutely no load on the engine to extend the cylinder. If there was a fault in a lock valve it would load the engine without moving the ram..

  3. #13
    Fabrication Guru +1 v8druid's Avatar
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    pull the plug and hot wire the solenoid you suspect control the pilot pressure to the dipper and see if it cures it .... if it does then you've proved your electrical issue theory.
    If it's got tracks, wheels, t*ts, or an engine, at some point it's gonna give you trouble!!

  4. #14
    Hey everyone, I know this is an old thread but I have the same machine with the exact issue. Iíve been trying to track down these solonoids that he mentions are under the cab. Does anyone know where exactly? Thanks

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