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Thread: Taiwanese Drill press capacitor
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12th Jul 2022, 11:57 AM #1
Taiwanese Drill press capacitor
My faithfull drill press is faltering. I mean it is nearly brand new bought in 1990 and has performed flawlessly .
The symptom is that when I switch on , the motor humms and buzzes and locks and will not rotate as it should. It does not do this at every start but mis starts are becoming more frequent.
I would like to to replace the cap with one of the best quality not one from China as they can't make electrical components well.
A European component of Japanese one is preferable but I am at a loss of where to look for one.
Can anyone offer a suggestion?
Thank you
Grahame
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12th Jul 2022, 12:59 PM #2Most Valued Member
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Element14 (used to be Farnell) or RS Components both have local branches and extensive online stores with quality components.
You might also find some NOS quality stuff on eBay.
I’ve had a reasonable run with capacitors from some of the larger eBay electrical sellers. Typically while they are Chinese components they are at least genuine components not just fakes.
Steve
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12th Jul 2022, 02:18 PM #3Member: Blue and white apron brigade
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+1 for Element14.
BTW Many of the Japanese branded ones are made in Korea or China and the Italian Ducati brand are now made in Romania.
Teh other place I have bought motor caps are irrigation and Pool pump stores
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12th Jul 2022, 03:17 PM #4
I might have to amend the statement in that case.
I opened the case and the capacitor is a product of Ming Fun Electrics Co. LTD.
It is marked 150 MFD W.V.250 V.AC.
Google says the cap is Taiwanese..
Thanks fellas I will try those places you have named.
Grahame
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13th Jul 2022, 09:15 AM #5Diamond Member
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150µF is quite large! How many HP is the motor???
Here is a VIC stockist of a variety:
https://captech.com.au/product/motor-start-capacitor/
and here are a typical range of small motor start caps:
https://www.jaycar.com.au/spend-30-o...r-start/c/200H
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14th Jul 2022, 08:25 AM #6
Hi Nigel,
Thanks for the heads up.
I have been carting the old cap all over the place looking for its replacement and that was the general comment from the counter staff along with, sorry we don't have one.
The motor is the original one that came with the drill press.
The data plate plate reads 55Kw.
4pole 1420 rpm manufactured in 1989.
I have owned the drill press since buying it new in 1990. I have never had to repair it other than new belts 18months back.
Years back I changed the motor mounting so it it pivots away from the d/press and the belts could be tensioned with a cam lock lever (can't think of the right name for the do hickey at the moment) and fitted a counter balance inside the hollow column for the table.
Those mods made it a pleasure to use.
The electricals have never been touched other than to tape them up when I spray painted the drill press.
I repainted it several years back in apple green from a spray can.
I did eventually score a cap at the electrical repairers but its physically bigger and I'll have to make a new enclosure for it.
I can only surmise some sort of factory fubar with fitting the correct spec cap when the drill press was made.
Surely if it has run for thirty years without complaint, it must be safe to fit a similar sized cap to what I have ?
Is there any potential danger to me?
Grahame
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14th Jul 2022, 09:11 AM #7Diamond Member
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55kW? Nearly 70HP? Wow!
(I suspect it is 0.55kW, which would be 2/3HP or 3/4HP,
probably the size of a 4L paint can in 1980 technology)
SAFETY ADVICE: Discharge the cap terminals with a screwdriver before removing/swapping
Anyway, from my limited experience in motor start caps, too large isn't an issue.
Too small will prevent it from starting reliably, but too large hasn't been a problem.
Here are some caps with physical sizes listed:
https://www.ebay.com.au/itm/151986919034
If the starting isn't reliable with the new cap., the centrifugal switch might be dirty.
(not that all 240V/single-phase have that switch, but 99% do)
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5th Aug 2022, 11:05 AM #8Most Valued Member
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5th Aug 2022, 11:33 AM #9Most Valued Member
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A cap in an AC circuit (inc a motor) will not store a charge.. DC circuits are a different story
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5th Aug 2022, 06:31 PM #10Most Valued Member
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Are you sure about that?
Chris
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5th Aug 2022, 09:42 PM #11Diamond Member
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Some motors have two caps.
The run capacitor will not store a charge, because it is wired direct across windings (which discharge it).
The start cap, however, has a switch. When the motor starts, the centrifugal switch opens, and the possibly charged cap is floating at whatever voltage was induced across it by the windings.
It does depend on the type of cap, though, as to how well it holds a charge?
P.S. I commented to Grahame that 150µF was quite large, but here is a recent 1/2HP motor:
IMG_3091.jpg
The caps are 14µF and 75µF. Based on that, 150µF isn't that large?
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5th Aug 2022, 10:05 PM #12
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5th Aug 2022, 10:18 PM #13Most Valued Member
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Reminds me of the “this is a capacitor - they can bite you bad” lesson that my sparky father gave me when I was about 10yo.
He had a metal case oil filled capacitor about the size of a pack of cigarettes, and proceeded to hook it up briefly to the wall socket and then disconnect it.
“Doesn’t look dangerous does it - now watch this” as he shorted the capacitor terminals with a screwdriver.
The resulting “crack!!” was indelibly etched in my memory and I’ve never forgotten the lesson which was to treat any decent size/voltage capacitor like it could kill you until you’d proven otherwise.
For S and giggles I just went out and measured the voltage on the start cap of my rotary phase converter which hasn’t been turned on in the last 6 hours or so.
Happily sitting there looking benign - at 180v on a 150uF capacitor.
Plenty enough to get your attention if you got across the terminals!!
Yes, I do need to install a safety discharge resistor across it….
Steve
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6th Aug 2022, 12:07 AM #14Most Valued Member
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Carry on, I can’t be bothered
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