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Electric motor problem on radial saw

GLAUCON's picture

I have a 10 year old Delta 10" radial arm saw that I use to cross cut boards to rough length before milling.  It is wired for 230V.  Last night I was cutting some 6/4 when the blade bound up at the edge of a knot, freezing. I cut off the saw within a few seconds, unplugged it and freed the wood from the blade.  I tried to restart it, but nothing happens- no sounds, movements etc.  There is a thermal overload protection so I left the saw to cool, but it still does not start, even after pushing the reset switch- which does not click.  I checked the panel and the breaker is fine, and I measure 240V at the saw switch (which I changed) with a voltmeter. The saw has occasionally bound up in the past, but it does not get much heavy use, so I'd expect the motor to take an occasional stress like this without failing.


Question is- is there anything else to check before buying a new motor?  I can't find any reference to any built in circuit breaker in the motor itself. Can the thermal overload protection fail and need replacing? It is a Philips motor (single phase) that can be wired for either 120V or 230V.  Given how bulky the saw and arm are, I don't really want to bring it back to a Delta service center if they are just going to replace the motor. It'd probably be simpler to just get a new motor and replace it myself.


Any suggestions?


Glaucon

Glaucon

If you don't think too good, then don't think too much...

RickL's picture

(post #98281, reply #1 of 6)

Bring it to an electric motor repair shop first. It might have a loose wire internally. Plus it can be rewound and could cost less than replacing possibly. That's where I usually start with motor problems.

dukeone's picture

(post #98281, reply #2 of 6)

Thermal overloads of the replaceable heater type have the heater go open with repeated tripping, which is its proper function. Pull the heater element out with the power off and ring it out with an ohmmeter. It is in series with the motor so an open would stop it from running. If it is the little red button type on the side of the motor and does not "click" it may have gone bad. Common brands for the little red type are Klixon or Hineman. Was the switch you replaced a standard two pole hp rated switch or a manual motor starter switch which contains the overload heater?
Good luck, Duke the Electrician

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KeithNewton's picture

(post #98281, reply #3 of 6)

If the switch does not click, I think you may have burned one of the heater in the switch. The motor is not getting any juice if the switch doesn't click.

Without being able to look into the switch it is hard to guide you if you are not familiar with the wiring. If you find where the wires that are coming out of the switch that go to the motor are connected, the little unit that these wires are connected to is normally the overload protection. They are designed to get hot and disconnect before your motor burns up, but sometimes they will burn out before they can
disconnect. Sometimes you can tell from the outside if the plastic is distorted or scorched, but you may need to take them out to tell.

If you have pressed the reset button, you should check continuity through the heaters. They should be normally closed circuits. if they are not closed this is the problem.
I hope this helps. Keith

GLAUCON's picture

(post #98281, reply #4 of 6)

Thanks for all the advice.  The switch I replaced is the on-off (DPST) switch on the front of the saw.  It is a bit cheesy, so I had a spare on hand, and I wanted to check to see if the saw was getting power, and pulled the switch to test potential upstream (240V). I replaced the switch with my spare on the off chance that it had malfunctioned.


 The thermal reset switch is the one that doesn't click.  It sounds like my best move is to pull the motor and check the integrity of the reset switch with an ohmeter after inspecting for obvious damage (melted plastic, etc).  If the reset switch is OK, I guess I'd either get a quote on local repair or order another from Delta.


Any other advice?- and thanks,


Glaucon

Glaucon

If you don't think too good, then don't think too much...

kensshop's picture

(post #98281, reply #5 of 6)

I am not familiar with the motor on your saw but I can pass along some tips I've learned after 30 years with a Dewalt radial arm saw.  Occasionally, for no apparent reason, it will not start.  After a couple of trips to the motor repair shop they showed me how to, with the saw unplugged, open the cover where the start-up relay and capacitor are.  A couple of times the wire connections have gotten flaky and required resoldering.  Once, I had to remove the relay and gently sand the contacts.  This problem is common in start-up relays.  Your saw, being newer, may not even use one.   I quickly learned that checking these things first, and correcting them myself, was a lot less expensive than paying the repair shop AND a lot less trouble than aligning the saw once I reinstalled the motor.  Good luck.  Ken

MarkRD's picture

(post #98281, reply #6 of 6)

Funny, the problem you describe with the non-starting motor, I have the same issue with my 50+year old walker turner jointer.

I open up the starting capacitor cover and give it a few gentle taps, take the belts off, spin the motor, then it works... (say a few magic words, do a small dance...)

Mark


Measure it with a micrometer, mark it with chalk, cut it with an ax.

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