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3650 table saw - capacitor

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  • 3650 table saw - capacitor

    Need some help here. 6-year old 3650 has worked beautifully. Last week I fried the run capacitor while doing a lengthy rip session with poplar. It melted so completely that I can't read the ratings on it. Can someone please help me with the MFD and VAC ratings required for this capacitor? (The motor is the stock TH100085, 1-1/2 HP, TEFC, wired for 120V.) I'm guessing I should go for something in excess of 400 for the VAC, but I don't know. Thanks.
    Last edited by FloridaHokie; 10-17-2011, 09:45 AM.

  • #2
    Re: 3650 table saw - capacitor

    First you have to know if this capacitor is a run cap or a start cap. Start caps are usually black plastic. Run caps are normally metal or white plastic. Start caps start at about 60 mfd and can go up to nearly 1K mfd. The mfd of a start cap is not as important as one might think. I have substituted a 440 mfd for a 161 and vice versa and had no problem starting the motor. Start caps are only in circuit for a split second then are removed with a set of points. Run caps are in line with the start winding all the time and are far more critical on the mfd value. If you think it's a start cap, you can try whatever you have handy. If the motor starts right up, no problem. If it lags, go bigger. Voltage isn't all that important either, but stay higher than the actual voltage your trying to run it on.
    Frequently asked questions about pumps and tanks.

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    • #3
      Re: 3650 table saw - capacitor

      The burned capacitor is the run capacitor. (...know this because the remaining good capacitor says "Motor Starting Capacitor" with ratings of 200 MFD and 250 VAC). The burned capacitor was black plastic, approx. 2-1/2" long by 1-5/8" dia.

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      • #4
        Re: 3650 table saw - capacitor

        That one sounds like a start capacitor as well. I can't remember ever seeing a black run cap. Do you know how the two caps were wired? If they were wired in series or parallel, it may be to double or cut in half the capacitance and use two caps to take the load instead of just one. Starting a saw motor may occur many times during operation if the operator really lugs the motor down. It can and will go back into start when the RPM's get low enough. Maybe it had two caps to make them last longer under these conditions.
        Frequently asked questions about pumps and tanks.

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        • #5
          Re: 3650 table saw - capacitor

          Not sure of the wiring in series as the wires for both capacitors disappear into the motor housing. I was really hoping one of you guys with a 3650 would take a look at your capacitors (just two phillips screws to remove cap covers) and tell me the ratings on them. The cap in question is the one closer to the saw.
          Click image for larger version

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          My motor is off the saw and upside down in this photo with both cap covers removed. The good cap is clearly marked, and the ratings uphold its status as a starter. The fried cap is truly fried, with the only legible marking being its fabrication date of 09/04. Ridgid has been no help, advising that they cannot recommend replacement of the capacitor.

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          • #6
            Re: 3650 table saw - capacitor

            I can't tell what that thing is, but I tend to agree with you on it being the run cap. Usually when they double up on starts, they are in the same housing. On jet pump motors that have a start and a run, the runs are all over the place, there doesn't seem to be any rule of thumb on size. With the capacitor start/run motors, the run cap ratings are usually 30 to 40 mfd. To take a wild guess, I would say try a 10mfd. If you have an amp meter, you can tell if it's running right or not.
            Frequently asked questions about pumps and tanks.

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            • #7
              Re: 3650 table saw - capacitor

              looks like a defective product to me. did you register it with the LSA? i think ridgid owes you a new motor, or should repair this one free of charge, provided it is properly LSA registered.
              there's a solution to every problem.....you just have to be willing to find it.

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              • #8
                Re: 3650 table saw - capacitor

                It's been a while, but I suspect I did register it...6 years ago. My literature cites a 3-year warranty. ...not likely a warranty claim will see any results.

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                • #9
                  Re: 3650 table saw - capacitor

                  If you do have to replace the motor, I wonder if it's a standard motor or something made especially for Ridgid. Some of these replacement motors can cost more than your house. And only theirs will fit without a major refitting.
                  Frequently asked questions about pumps and tanks.

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                  • #10
                    Re: 3650 table saw - capacitor

                    Cost at a Ridgid service center for the motor alone starts at around $400. I can get the entire saw, lightly used, with motor, starting at around $250. Shoot...Home Depot was fire-saling these saws, new, for under $200 a couple years back. ...and all this for want of a $12 (more or less) part. Can someone please rescue me from this insanity...

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                    • #11
                      Re: 3650 table saw - capacitor

                      I didn't know it was a big box saw. That probably means OEM motor.

                      I can help you with a run cap. I can't guarantee what value it needs, but I'm guessing 10 mfd. I have them from 5 mfd up to 60 mfd.
                      Frequently asked questions about pumps and tanks.

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                      • #12
                        Re: 3650 table saw - capacitor

                        FloridaHokie, I just took a look at my capacitors on my 3650. The outside one, easiest to get at, is labled "Motor Starting Capacitor" is gray in color and is 200 MFD and rated 250VAC. The inner capacitor is black, 30 MFD and rated at 350VAC. Hope this helps.
                        When seconds count, the police are only minutes away.

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                        • #13
                          Re: 3650 table saw - capacitor

                          DSurette.... You are a Godsend. Thank you for your help.

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                          • #14
                            Re: 3650 table saw - capacitor

                            Im so glad someone could help you so now I can vent. Hey dumb dumb are you seriouse "sizing start caps isnt that critical". Put an oversized one on and the contacts or as you say points will pit/burn prematurely, the windings will break down prematurely, the inductance will prematurely harm the run cap. It worked for me is your anticipated response, right. Plumbing without vents works for handymen, why should we do anything right just make it work!

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                            • #15
                              Re: 3650 table saw - capacitor

                              Who the hell are you calling dumb dumb? I didn't see you trying to help this guy with his problem. I've only been in the motor business for 25 years, so what do I know. We only do about 300 bearing jobs a year, replace hundreds of start caps, run caps, centrifugal switches and start points. Changing the value of the start cap in a pump motor or any motor similar will not do nearly as much damage as the manufacturer has already built into that motor. Wheres your credentials?
                              Frequently asked questions about pumps and tanks.

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