Posts: 6
Threads: 0
Joined: Aug 2021
Visiting a friend who owns an old Hitachi miter saw that's not working. He said that one day it simply stopped running - electrical issue. Using a multi-meter I've checked from the power plug to the brush housing and have continuity and 120V power. The brushes, although worn a bit, also show continuity. I'm guessing that if it simply stopped running, rather than sparking and/or smoking, that it's gotta be a broken or unsoldered wire connection downline from the brushes. The commutator is a bit carbonized, but I get readings with the Ohm meter.
The current issue is that I have no idea how to remove the rotor to inspect the coil connections and clean the commutator. Anyone here have that knowledge???
Posts: 14,812
Threads: 10
Joined: Jan 2010
Location: southeastern VA
08-20-2021, 03:27 AM
(This post was last modified: 08-20-2021, 03:30 AM by iclark.)
Is the switch on the hot side or the ground side of the power? Have you used the multimeter to check for continuity across the switch (with the saw unplugged)?
Saws often seem to quit working because of sawdust accumulating in the switch.
Have you tried spinning the blade by hand and then turning on the switch (with your fingers out of the way) while the blade is spinning to see if the saw runs then?
If the switch is good, then search the net for a parts diagram for that model and see if it has a starter capacitor.
"the most important safety feature on any tool is the one between your ears." - Ken Vick
A wish for you all: May you keep buying green bananas.
Posts: 6
Threads: 0
Joined: Aug 2021
(08-20-2021, 03:27 AM)iclark Wrote: Is the switch on the hot side or the ground side of the power? Have you used the multimeter to check for continuity across the switch (with the saw unplugged)?
Saws often seem to quit working because of sawdust accumulating in the switch.
Have you tried spinning the blade by hand and then turning on the switch (with your fingers out of the way) while the blade is spinning to see if the saw runs then?
If the switch is good, then search the net for a parts diagram for that model and see if it has a starter capacitor.
I checked all components for continuity from the plug through the carbon brushes, both individually and as a system. I also plugged it all back in and got 123V at the brush mounts when squeezing the trigger switch.
There is no starter capacitor for this type of motor.
I'm just trying to get the rotor out to see if and where there is a broken conductor and to clean the carbon off the commutator, but haven't had any luck removing it as yet. There's something holding it tight and I'm not gonna start prying with a screwdriver to see what happens. Hoping someone here knows how.
Posts: 14,812
Threads: 10
Joined: Jan 2010
Location: southeastern VA
The manual
here includes a parts breakdown.
It might give you an idea for a hidden screw or retainer that will let you take it apart.
I hope that someone else here can help.
"the most important safety feature on any tool is the one between your ears." - Ken Vick
A wish for you all: May you keep buying green bananas.
Posts: 6
Threads: 0
Joined: Aug 2021
Thanks! That's the clearest copy of the manual I've seen. Most look like they're 10th generation scans... I'll take a more clued-in look.
Tom
Posts: 6
Threads: 0
Joined: Aug 2021
Slight change in my Google search terms and I stumbled upon a video of a complete restoration of this saw, including how to remove the rotor. Time to get to work.
https://www.youtube.com/watch?v=Yx3HlbyH...AmateurDIY
Posts: 1,991
Threads: 1
Joined: Aug 2016
(08-21-2021, 10:31 AM)tomherrick Wrote: Slight change in my Google search terms and I stumbled upon a video of a complete restoration of this saw, including how to remove the rotor. Time to get to work.
https://www.youtube.com/watch?v=Yx3HlbyH...AmateurDIY
See if the brushes are free in the holders. I have seen where crud would hold the brush just clear of the commutator. Roly
Posts: 6
Threads: 0
Joined: Aug 2021
Hmmmm, interesting... I will check that out.
Posts: 6
Threads: 0
Joined: Aug 2021
OK, Roly, that was it. This saw needs a lot of work - and I'll do a restoration on it for my friend who has done so much for me - but now know that it will at least run. Some 600-grit emory paper folded and guided with a narrow flat screwdriver cleaned it out enough for both brushes to do what they do.
Thanks for your insight.
Posts: 1,991
Threads: 1
Joined: Aug 2016
(08-21-2021, 02:57 PM)tomherrick Wrote: OK, Roly, that was it. This saw needs a lot of work - and I'll do a restoration on it for my friend who has done so much for me - but now know that it will at least run. Some 600-grit emory paper folded and guided with a narrow flat screwdriver cleaned it out enough for both brushes to do what they do.
Thanks for your insight.
Glad it worked. Roly
