Radial Arm Saw motor gone wonky

kopeck

Member
My old trusty Sears 10" Radial Arm Saw is acting strange. It's running backwards, very slowly and then it trips the internal breaker.

We had a lightening strike really close by, like on my property. I suspect that's whats caused the problem.

Maybe a bad capacitor?

K
 
Sorry I cant help you with your motor problem but
if the fix commands much money be sure to check
your local Craigs list before you buy parts as
radial arm saws don't bring much money these days,
at least around here. I just bought a real nice 10"
cast iron Delta on a factory roller cabinet full of
accessories including a brand new $300 Dado set for
$65 and there is always a bunch of Sears saws
starting at $50
 
Thanks for the ideas guys. I'll pull it off and blow it out. This is an old Craftsman, back when they made heavy stuff. I like to keep it around to cut wide boards.

Jim in MA:

I'm in Maine, the motor I have has H68 stamped on the plate. Is that the same as yours? If so I would probably be interested if you were willing to drop it in a box?

K
 
I'll check later and get back to you.
If it will work, You can have it if you pick it
up.
I'm just off rte. 95 exit 56
 
The current sensing switch that enables the start winding with
the startup capacitor went out on me and I simply wired it to a
hefty front panel switch to manually switch the startup cap and
winding in and out.

When I am sawing big stuff I leave the switch on for more
torque when the motor slows down.

Greg
 
I was able to get my hands on an analog muti-meter and it looks like the capacitor checks out. I guess that means the start switch. I'll try blowing it out and go from there.

Do you guys think the lightning strike could have caused this or is it just bad timing?

I did notice the on/off switch was wired backwards. That is the neutral was on the switched terminals and the hot line was on the pass through terminals. I had to have been like that for years though.

K
 
If you've never opened an electric motor, this is a good chance to learn.

First is to mark the endbells & frame with a center punch or screwdriver; just mark the endbell and frame so it will be easy to align each endbells when you put it back together.

Pull off the end bells to check the start switch. Lightning may have burned the contract; just touch them up with emory cloth or a fingernail sanding stick so they will make contact again. Also check for broken or burned off wires as much as you can see from the ends.

If the centrifugal switch and collar look okay, put the endbells on the frame and close up motor.
 
Emery on emery cloth is conductor, it should NOT used on electric contacts, or anything electric.

Dusty
 
K,
My motor does NOT have a centrifugal switch, only a current
sensing switch in the radial arm by the cap.
My motor is inductive with no brushes.

Hope you can fix yours,
Greg
 
(quoted from post at 09:19:56 10/25/14) K,
My motor does NOT have a centrifugal switch, only a current
sensing switch in the radial arm by the cap.
My motor is inductive with no brushes.

Hope you can fix yours,
Greg

I'm pretty sure mine is like yours. I had it apart 6 or 7 years ago and I don't recall brushes or really much of anything inside.

There is a plastic box with terminals that sits beside the capacitor.

I'm wondering if it's that switch.

Here's the parts breakdown:

http://www.searspartsdirect.com/par...5/00003?blt=06&prst=0&shdMod=11329411

K
 
Bill, I don't understand why your clock isn't running backward. I figured out a long time ago, you aren't wired right.
George
 
Yes when power is turned on the startup current activates the
switch to energize the start winding with a phase shifted voltge
developed through the cap.
Like I said, I bypassed the current sense switch and ran the
start winding with the cap in series to a manual switch on the
front plate of the arm.
When it reaches running speed I switch off the start winding.
When the motor bogs down in thick stuff I turn it on.

Greg
 

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