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1660Re: [sawsmith] Re: Messed up my saw

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  • RedfieldRH@aol.com
    Oct 10, 2012
      Great tip! I didn't realize there was a relay.

      My understanding of motor starter functions are that some had a centrifugal starter switch that was closed on startup and powered a separate set of starter windings to increase starting torque. When the rpm increased the centrifugal force switch off this winding and the normal windings took over. However, from what I know this type of starting system is not common now and has been largely replaced with the capacitor start types (among others).

      I always thought the capacitor start system stored a charge in the capacitor to provide a momentary high current surge to overcome starting torque but my engineer friend said no, the capacitor actually functions to shift the phase of the magnetic field to increase starting torque and drops out somehow when up to speed. I have never seen relays on cap start motors, but it makes sense that this would be one way to control the capacitor effect. This would also explain the normally on mode of the relay.

      I used to diagnose and fix relays all the time on cars. That was back when they were still mechanical and not solid state. The relay boxes often even had a basic schematic printed on the cases, which you could actually open, test and repair! Imagine that...

      Hope this helps,


      -----Original Message-----
      From: Carl Finch <barkingcoyote@...>
      To: sawsmith <sawsmith@yahoogroups.com>; sawsmith <sawsmith@yahoogroups.com>
      Sent: Wed, Oct 10, 2012 1:33 am
      Subject: Re: [sawsmith] Re: Messed up my saw

      At 03:33 PM 10/9/2012, Robert Berschauer wrote:
      >It did come from the motor...I popped the cap on the motor and see
      >there is a relay and a motor starting capacitor in there...I am
      >wondering if the relay made the sound...I don't see a way to open
      >the relay to examine it...do they make replacements still that will
      >work with that motor?

      Here's an excerpt from a post of mine, addressing the repair of the
      relay (since there seemed to be nothing available as a replacement back then):

      At 12:16 PM 7/28/2004 -0700, I wrote:

      Didn't have much luck searching for that 40 year old relay.

      Then I noticed the slotted screw in the top of the case.

      I'd been concentrating so much on the bottom of the case, where the all the
      wire connectors are, that I'd never noticed that the darn thing could be
      opened (and anyway, so much stuff is sealed for life nowadays).

      Located my 'point' file (remember when cars had points?) and cleaned the

      But I discovered that the relay contacts are normally *closed*. They open
      almost immediately when the saw is turned on. So apparently the capacitive
      windings are active only for a fraction of a second, just enough to get the
      armature turning. (If anyone can set me a bit straighter on this, I'd be
      pleased to listen!)

      Anyway, got my Sawsmith back!


      in Medford, Oregon

      > I was also wondering if there was some king of fusable link
      > in-line in the motor that would blow. I am too new with this saw
      > to understand much about it.
      >On Oct 07, 2012, at 02:55 PM, RedfieldRH@... wrote:
      >>If your breaker did not trip, then the motor probably is not
      >>shorted out (which would draw heavy current). Is the click
      >>definitely in the motor? I know the original push button switches
      >>can fail. Mine did this, where I had to stab the on button to get
      >>the motor to stay on.
      >>I found that an easy replacement was to mount a low profile plastic
      >>electrical box on the top arm over the push button switch and use a
      >>paddle switch. I really like this arrangement and there are other
      >>options mentioned in previous listings.
      >>If you are comfortable with electricity and can get to the motor
      >>leads, you could rig up a safe, temporary power source to the motor
      >>(cord with wire nuts, etc.) to test the motor directly. Only do
      >>this if you are completely comfortable working with electricity.
      >>I don't believe there is a safety thermoswitch in these old motors
      >>although I am not positive. Many more modern motors have a button
      >>that pops out if they overheat.
      >>Hope this helps,
      >>-----Original Message-----
      >>From: rberschau <rberschauer@...>
      >>To: sawsmith <sawsmith@yahoogroups.com>
      >>Sent: Sun, Oct 7, 2012 4:13 pm
      >>Subject: [sawsmith] Re: Messed up my saw
      >>The click was in the saw motor, the house current is fine...no
      >>breakers tossed.
      >>--- In <mailto:sawsmith%40yahoogroups.com>;sawsmith@yahoogroups.com,
      >>"don_liechty" <3ddesign@...> wrote:
      >> >
      >> > Check your fuse box.
      >> >
      >> > --- In
      >> <mailto:sawsmith%40yahoogroups.com>;sawsmith@yahoogroups.com,
      >> "rberschau" <rberschauer@> wrote:
      >> > >
      >> > > I was given a my 1960 shopsmith radial arm saw by a
      >> relative...wasn't paying attention, bound the blade, heard a
      >> "click"...now it is not working. No hum, just dead...any ideas on
      >> what I can do (I do want to fix it. Any advice for the idiot is
      >> welcome...lesson learned.
      >> > >
      >> >

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