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small drill press motor problem

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Dave Smith

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#1
I have a small drill press that I bought with a previous problem--he had to plug it in and then spin the motor for it to start---I took the motor capacitor off and checked it with the ohm meter---it showed nothing---so my question is the motor bad even if it runs real smooth and quiet after spinning it or is the capacitor the problem ?--made in China --110 volt 1/3 hp single phase 60 hz 1600 rpm 2.3 amp--the SH capacitor ch0003269-92----I can just replace the motor with a used one I have but the motor on DP is only 4 1/2 inches OD so I would have to modify the mounting and belt cover guard ---if it is the capacitor do I need to get the same exact one from China or a generic replacement and is this a start or run capacitor?---thanks Dave
 

jwmay

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#2
Sounds to me like you need a new capacitor. I’d recommend buying the same one to replace it. I’ll hazard a guess that it’s a start capacitor, seeing as how it runs once it’s spinning. But honestly it doesn’t matter what it is, so long as you replace it with same.
 

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#3
If you match the ohms and voltage you should be fine. Original replacement may not be feasible.
 

Dave Smith

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cathead

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Dave,

There are several tests one can do with an ohm meter to test capacitors. If you simply connect the meter to the
capacitor, it should have infinite resistance(no conduction). It is also very helpful to reverse the leads and watch the needle
as you connect the meter. You will see the needle rise up somewhat and fall again. This tells you the capacitor is
working. When you first connect the ohm meter to the capacitor, you are essentially charging it up with the battery in the meter.
Reversing the leads charges the capacitor in the opposite polarity and what you see on the meter is the current rushing back
in the opposite direction. The higher the ohms scale you use, the larger the blip on the meter. I generally use the x100 or x1000
scale to do this sort of test. Of course one has to use an analog type meter to perform these tests.
Another handy thing to do is to compare the "blip" on a known good capacitor of the same size to one you have in question. If the
capacitor in question has a significantly smaller blip, one could suspect it has less capacitance and likely not good.

A capacitor that shows resistance when connected to an ohm meter tells me it has leakage and not good.

Also, any testing in this manor must be done out of circuit.

It's a good idea to discharge a capacitor before testing it for two reasons:
#1 Your safety
#2 If the capacitor has a high voltage charge, it could ruin an analog meter.

Digital meters have their place but can't do what an analog meter can do in this instance.



All that said, the capacitor is likely bad if the motor runs after you spool it up.
 

CluelessNewB

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#6
If you match the ohms and voltage you should be fine. Original replacement may not be feasible.
Not exactly...

Capacitors don't have "ohms" the units for capacitance are "Farads". A Farad is very big unit so you will typically see motor starting capacitors rated in "microfarads" and they typically cover a range like 88-108 microfarads. You should try to find a replacement with a capacitance as close to the original as possible (bigger is not better). The voltage rating should be the same or greater (bigger is fine).
 

Dave Smith

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Not exactly...

Capacitors don't have "ohms" the units for capacitance are "Farads". A Farad is very big unit so you will typically see motor starting capacitors rated in "microfarads" and they typically cover a range like 88-108 microfarads. You should try to find a replacement with a capacitance as close to the original as possible (bigger is not better). The voltage rating should be the same or greater (bigger is fine).
this one is 18 uF is this the Farad number and what does the u stand for ? or does the number CH0003269-92-SH mean 92 is the microfarad number ?---thanks Dave
 

cathead

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this one is 18 uF is this the Farad number and what does the u stand for ? or does the number CH0003269-92-SH mean 92 is the microfarad number ?---thanks Dave
Dave,

The u stands for Micro and is a specification for one millionth of a farad(F). Your capacitor is an 18 microfarad capacitor. There is usually
a voltage rating as well so the replacement needs to be at least the voltage rating of the old one. There would be some latitude in the size (uF)
as well lets say somewhere in the 15 to 25 should work. I could tell you more if you took a photo of the old capacitor.


I just looked on E-Bay and there are lots of 18uF capacitors for motor starting there. If yours is a metal can, it probably is an oil filled capacitor.
 

David S

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#9
Just a thought. If this is a capacitor start motor, it is likely to also have a centrifugal switch to disconnect the starting cap as it gets up to speed. Is it possible that the contacts are dirty, worn, or the switch itself is not functioning correctly?

David
 

Dave Smith

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thanks I found them on e-bay and the round type like mine are just a little too big to fit in the housing---I will look to see if I have one 15 to 25 in my supplies--thanks for all the information , and since it looks new I don't think contacts inside the motor would be dirty
 

David S

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#11
Dave you can always verify with an ohmmeter, just to be sure.

David
 

chips&more

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#12
Dave, are you sure in ALL YOUR PILES you do not have a meter that reads capacitance? Most modern digital multimeters have that function. If you don’t have one, they are cheap enough and should fit in a cubbyhole space on your bench:)…Dave
 

Dave Smith

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Dave, are you sure in ALL YOUR PILES you do not have a meter that reads capacitance? Most modern digital multimeters have that function. If you don’t have one, they are cheap enough and should fit in a cubbyhole space on your bench:)…Dave
Dave--I have at least 5 or six analog meters and at least 8 of the free HF digital ones and they were not in any of my piles---I did need to put new batteries in my analog meters to check the capacitor--I knew the capacitor was no good, but I didn't know if the motor may have also had problems---all my other used fractional motors with capacitors were all a lot higher microfarads so I am ordering an 18uf one now---even though I'm sure somewhere in all my electrical piles I have some capacitors--this is when being unorganized is frustrating--I am only 74 so I have a long time left to get organized, I'm working daily on it so am gaining---Dave
 

chips&more

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Dave--I have at least 5 or six analog meters and at least 8 of the free HF digital ones and they were not in any of my piles---I did need to put new batteries in my analog meters to check the capacitor--I knew the capacitor was no good, but I didn't know if the motor may have also had problems---all my other used fractional motors with capacitors were all a lot higher microfarads so I am ordering an 18uf one now---even though I'm sure somewhere in all my electrical piles I have some capacitors--this is when being unorganized is frustrating--I am only 74 so I have a long time left to get organized, I'm working daily on it so am gaining---Dave
Dave, if the HF digital is what I’m thinking of, then sorry, it’s one of the few digitals that cannot test for capacitance. And if you are working on cleaning up your piles? You are way ahead of me! I’m not gaining, the piles are winning! Good Luck…Dave
 
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markba633csi

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#15
Dave it's probably a run capacitor to have a value that small. And it's probably a permanent split-cap type (also called capacitor run) motor; no centrifugal start switch inside
Mark
 
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