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Electrical problem with a lathe.

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  • Electrical problem with a lathe.

    This is the information about the lathe. SAN-YUEN, SY-SAG 1700H, MFG 4-1-05, 197612. The lathe measures about 14" x 40".

    The lathe was working find for about 7 years then it quit working. I checked the fuses and they are all good. The ON switch is ON. Pull the lever UP or DOWN to run forward or reverse and it does not run. If I push the left relay in by hand it runs forward. If I push the right relay in by hand it runs in reverse. There are no wires off in the electrical box. On/off switch tests good. Forward/reverse switch tests good. Relay contacts all test good. 120 Volt AC circuit works.

    I have no electrical circuit drawing where can I get one?

  • #2
    probably be a safety switch somewhere ..on a door ..or the guard or deadmans or the emergency stop that has quit.

    all the best.markj


    • #3
      Many of these lathes have a magnetic safety interlock to prevent the lathe from starting up in the event of a power failure (when the power is restored, you don't want it starting up on it's own). My Grizzly 1031 has such an interlock, which also must be reset if you use the emergency stop. If this is the case, and yours has failed, iirc Grizzly sells generic replacements....


      • #4
        Does it have a brake pedal? There may be an interlock switch on the brake.


        • #5
          I would double check all the connections on the switch itself. I had a similar problem, and found almost every connection to be barely snug,some, almost falling off. Not a problem since. Worth a try. Bob.


          • #6
            Try Grizzly for manuals, not for yours but for one of theirs that 'looks
            like' yours for a start. Look at the 12x36 also as these are so close
            to 14x40 you can't tell the diff without a ruler. My 12x36 did the same
            thing, one of the contactors went open coil. Pushing on the button
            on top made the lathe run. Removal was a PITA, but I did make my own
            wiring diagram. There were three contactors on mine, all the same
            KM1 (ON/Forward) KM2 KM3, can't recall one for reverse, one for jog.
            I subbed the jog for the bad one. Contactors were chinese knockoffs
            of a Siemens contactor. FWIW I noted the pwr xformer had a 27VAC
            coil and a 6 VAC coil (for the lights). Contactors were 24-27VAC coils
            but were wired across both secondaries and the coils saw 33Vac.
            Suspect this was a cause of the failure and rewired the coils to see 27 V.
            The ON contactor is powered any time the pilot lights were on.


            • #7
              Sounds like the power side is good- motor runs either direction properly when the relays are manually operated. Maybe you have a low voltage failure, or like others have said possibly a safety switch is not being clicked. Might be a door or cover switch- either gone bad or mechanically sticking or not being activated.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


              • #8
                Press the "Reset" on the contactors (what you are calling Relays) and it should run fine

                Don't worry - that 1 catches all of us


                • #9
                  OK, everything is "good", unit does not work. Been there , seen it.

                  Do you KNOW that there is power applied to the contactor coils when the machine should be running?

                  That's the first check to make. If no power to coils, then there is a problem somewhere, possibly with an interlock. Your job is to find it by working back from there.

                  if you DO have power to the coils, check their resistance. Unlikely both would be bad, so this is mentioned only for "completeness".

                  Keep eye on ball.
                  Hashim Khan


                  • #10
                    Are the contactor coils, low voltage (24vac) or line voltage (120-240vac)? If low voltage is the transformer providing the coil voltage working? Does the transformer have a fuse in-line with its primary? A photo of the control box would be helpful.


                    • #11
                      Originally posted by gary350
                      If I push the right relay in by hand it runs in reverse. There are no wires off in the electrical box. On/off switch tests good.
                      So it runs therefore power to associated parts.
                      Try the actual lever and mechanism making and breaking contact with the two micro switches, usually some form of cam.


                      • #12
                        I have a Grizzly 14 x 40 lathe. Don't know if it is the same manufacturer but here is some information that may help. There is no interlock between the forward and reverse contactors. DO NOT PUSH BOTH AT THE SAME TIME. There is a plate that covers the belt drive and motor at the base of the head stock. Mine had one louver in it. I live in a very hot and humid area. With only one louver in the panel there is no place for the air flowing over the motor to go. The result is the motor overheated and burned up. I added more louvers to the cover. Made a big difference in the motor heat.

                        That is not your problem since you can make the lathe run but is something to be aware of.

                        Can you hear a buzzing when the power is on the coils for the contactor? The voltage is 120 volts on mine. If no buzzing the coils probably have no voltage.

                        Remove the end panel that covers the gear train. There is an interlock that is closed by the cover, located at the lower rear of the opening.

                        The forward/reverse lever operates a cam that move to close a micro switch, one for forward and one for reverse. The cam may be loose on the shaft. There is a key that connects the handle to the shaft. I have had that key fall out because the set screw backed off. The handle moves and the shaft moved a little because of a burr but the shaft doesn't turn enough so the micro switches were not actuated. This is worth checking.

                        Check the Grizzly site for a lathe like yours and see if they have a manual. the manuals have wiring diagrams. I have the wiring diagrams somewhere but don't know where the manual is right now.


                        • #13
                          check the micro-switches at the end of the for/off/rev rod. they could have gone out of adjustment or bad. i could make my lathe do everthing it was supposed to by pushing the resets with a stick. i traced it to a micro-switch at the end of the control rod. after replacement, i had to fiddle around until i got it adjusted right.


                          • #14
                            Have you found the problem yet or are you going to scrap the lathe?