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Hitachi EX 120-3 electronic schematic or resistor value needed!

Joined
Aug 19, 2022
Messages
4
Location
Euclid, Ohio
Occupation
Electrical Contractor
Hey wondering if anyone can help me out, good friend of mine has the Hitachi EX 120-3, 1995 or 1996, burned out a resistor on the PVC unit. It's R1 and I cannot find a schematic anywhere. Downloaded two different shop manuals and neither of them show any electronics. I ohmed it out and one day it was 700 ohms and the next it's 300. He lives in Montana and I live in Ohio, don't want to take a chance and mail it all the way out there with the wrong one installed. The resistor is discolored so I cannot tell by the bands what the value is.
 

mg2361

Senior Member
Joined
Jul 5, 2016
Messages
5,124
Location
Pennsylvania
Occupation
Equipment Mechanic
Welcome to HEF Roberto;)!

10 ohm - 4 Watt resistor. That is part of the 5 volt sensing circuit. It usually fails because the F7 1A fuse keeps blowing and someone may have put a larger amperage fuse in (which should never be done). The underlying cause is usually a short to ground in the wiring or in a sensor.
 
Last edited:
Joined
Aug 19, 2022
Messages
4
Location
Euclid, Ohio
Occupation
Electrical Contractor
Thank you for your quick response! Totally makes sense, my buddy told me a technician had to modify a harness he bought online to make it work. Really can't thank you enough!
 

mg2361

Senior Member
Joined
Jul 5, 2016
Messages
5,124
Location
Pennsylvania
Occupation
Equipment Mechanic
Post a picture of your fuse box. The F7 should be the fourth one down on the left when looking at the fuse box.
 
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