Another Sears Radial Arm Saw Motor Problem

When attempting to power on the Sears RAS (circa 1977) set for 110V, it instantly throws the 20 amp dedicated breaker with no rotation or hum at all. The saw was working fine moments before the failure. I was just doing a couple of crosscuts (i.e.no extended hard cuts). Based on previous posts, here's what I've done so far:
1) tried the saw on another 20 amp dedicated breaker, same results (no extension cords in use) 2) took off the case, cleaned all saw dust out with a compressor 3) "sniffed" for burnt windings (no smell at all) 4) inspected all internal and external wires for nicks, scraps, pinches, etc, (wires look good) 5) Did a basic VOM test on the starting capacitor (seems to check out) 6) Reviewed the "breaking/starter" switch, points are a bit rough and I do see an arc at this point during testing. Is this arcing a symptom of bad windings, etc. or could the arcing itself be the source of thown breaker????
Any help greatly appreciated, Mikemcg PS..First post...Hope I followed proper protocol :)
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snipped-for-privacy@charter.net wrote:

(snip)
What does "seems to check out" mean? What readings did you get?
With the capacitor disconnected and with the meter set to the highest OHMS setting you should see a small kick of the needle and the reading should then go to infinity as the capacitor charges. If you get a resistance reading other than infinity once the capacitor is charged the capacitor is shorted.
--
Jack Novak
Buffalo, NY - USA
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Using your cap test with the VOM set at 2000k, i get a digital spike of about 1000 but it never returned to infinity or for that matter started to approach infinity. One other curious thing I failed to mention, the saw will trip the breaker even without the power switch on....
Thnanks for the reply.... Nova wrote:

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If the saw trips the breaker without it's power switch on (like when you plug it in with the power switch in the off position), then the problem is NOT the motor. It's a short somewhere in the line cord, plug, or wiring leading to the switch.
--
Charley

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You have a short.

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I would have agreed with the wire/switch short conclusion, but here is a test I did this morning. I disconnected the main WHITE and BLACK wire from the wiring connector block to isolate the 110V cord and user power switch from the motor. There is no continuity between the WHITE at the terminal block end and the BLACK at the plug end (and vice versa) regardless of the position of the user power switch. Doesn't this rule out a short in the 100v wiring and/or power switch?
Thanks, Mike CW wrote:

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snipped-for-privacy@charter.net wrote:

No.
You tested only for a hot-to-neutral short. You didn't test for, and therefore haven't ruled out, a hot-to-ground short.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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What brand of receptical are you pluging it into? I had a similar problen several years ago after some ham handed carpenters doing some work at my house yanked theirplugs out at an angle and broke the plastic insulating material. When you then tried to plug another cord into the recpt. it would short and trip the breaker. The recpt's were Hubble.
Chuck P.
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With the help of this usenet group and additional ideas, I have identified the problem. It indeed was a short to ground. There is "start switch relay" that had plastic standoffs on both sides of the relay tab as an insulation off of the frame (ground). Over the last 27 years, heat had slowly melted the 1/8" thick plastic tab to less than 1/16" of an inch until the relay tab actually fused to bracket attached to frame ground. Voila, short! I've identified the part at a Sears webpage. Hope to order it tomorrow, but if it's unavailable I'll fabricate small teflon insulation "dots" and glue them to the existing plastic.
Thank you all for the guidance and ideas, Mike
MOP CAP wrote:

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Just a comment, and not relevant to your problem, but if you are in the US you might want to take a look at http://www.radialarmsawrecall.com /. If your saw is affected it gets you a new blade guard and table, for free.

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