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Old 08-22-2011, 03:26 PM   #1
wilywizzzz
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Default how to test capacitors on motherboard with a multimeter

Friend of mine gave me motherboard not working.
I can't see if any of the caps are bad cause he washed it with hot water.

Is their any way to Use a Multimeter to Test a motherboard caps.
Thank you for all your info.
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Old 08-22-2011, 10:27 PM   #2
PCBONEZ
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Default Re: how to test capacitors on motherboard with a multimeter

You can tell a little bit [if you remove the cap] but not enough to know if the cap is good.

Obviously if your meter has a capacitance function you should check that.

DC check....
Put the meter on ohms and connect, let cap charge from the meter. [#s will stop going up]
Reverse leads, watch cap discharge then charge again. [#s will go down then up.]
Reverse leads again, watch cap discharge then charge again.
- Very hard to do with a digital meter. An analog meter is better for that because you can watch the needle. Digitals usually just look like numbers flashing. It helps w/a digital to change/experiment with the ranges to find one with a slower charging rate.
-
If no charge and discharge the cap is either open or shorted and the reading will tell you which.

ESR is an AC property.
The DC check can be fine but the ESR still be totally screwed.
Caps with high ESR can make a board unstable or not run at all.

If you don't have an ESR meter
- and since you have to pull the caps to check them with a multimeter anyway
- it's best just to replace any brand/series cap with known problems.
.
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Old 08-23-2011, 06:02 AM   #3
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Default Re: how to test capacitors on motherboard with a multimeter

Thank you very much.
Enough info being said.
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Old 09-19-2011, 12:38 AM   #4
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Default Re: how to test capacitors on motherboard with a multimeter

I've seen multimeters which can measure capacitance, and I was tempted to buy one from lowes, but i didn't understand the range of capacitance it could detect. it stated it could detect in the nano range up to 4 mf- now is m for micro or milli? Sorry if this is a dumb question but if it were micro i would think they'd use mu. (some stores state 100mf on their sites to stand for micro farad, hence my uncertainty- I think it was this model specifically: http://www.amazon.com/Ideal-61-312-R...6414091&sr=8-2)

Does anyone have a suggestion for a not too expensive multimeter that can detect capacitance from 10 to 1000 μF ?

Thanks!
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Old 09-19-2011, 01:40 AM   #5
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Default Re: how to test capacitors on motherboard with a multimeter

1 Farad = 1 F
1 Farad = 1,000 mF [Millifarad ]
1 Farad = 1,000,000 F or MFD [Microfarad] - Some incorrectly use MF [w/a capital M]
1 Farad = 1,000,000,000 nF [Nanofarad]
1 Farad = 1,000,000,000,000 p [Picofarad]

Dunno where they got the 4mf from.
Link below shows it's ranges are: 40.00nF / 400.0nF / 4.000F / 40.00F / 400.0F
http://www.idealindustries.com/prodD...?prodId=61-312

I use a separate meter for capacitance. [Run like $20-$50 on eBay used.]
DMM's I've seen with a capacitance function have pretty lame capacitance functions IMHO.
Really need one that's good to at least 5000uF to cover those 4700uF that are common place.
Not many [if any] DMM's go up to that.
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Old 09-19-2011, 02:07 AM   #6
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Default Re: how to test capacitors on motherboard with a multimeter

A separate capacimeter, or better an LCR meter will be better than just a DMM.
But please note that it will not measure capacity on-circuit most of the time.
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Old 09-21-2011, 03:00 PM   #7
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Default Re: how to test capacitors on motherboard with a multimeter

Thanks for the explanations and advice!
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Old 09-22-2011, 05:16 PM   #8
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Default Re: how to test capacitors on motherboard with a multimeter

You can certainly check if the surface mount cap is good or bad. Connect the negative lead to ground and the positive to ends of the cap alternatively,
1 end of cap will give a beep sound and the other end will give some value this means most probably, the cap is fine, but.... both end beep or both end value or no beep at all means the cap needs replacement.
But still, ESR meter is must when you are playing around with capacitors.
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