Capacitor question ?

[bianchi77]

Guys,

Are these capacitors bad ?
I got 12.4 ohms and high pitch beep all the time for all of them...

Any ideas ? It's MSI LGA775 mainboard, I can't see what's the type of this board,
and the caps is 820uF/2.5V

[ReeceyBurger123]

Re: Capacitor question ?

11.4 ohms on an esr meter or DMM ?

[bianchi77]

Re: Capacitor question ?

DMM and it's in circuit ....

[bianchi77]

Re: Capacitor question ?

It's MSI 7525 motherboard LGA 775...

[diif]

Re: Capacitor question ?

You need to use an ESR meter to measure the ESR. Measuring the resistance in circuit with a DMM is pointless.

[bianchi77]

Re: Capacitor question ?

I have capacitance meter....can I use it in circuit ?

[diif]

Re: Capacitor question ?

You need to measure ESR also. Often caps are within their capacitance rating but way off with their ESR.

[bianchi77]

Re: Capacitor question ?

Is it possible doing it in circuit ? or I need to remove it off circuit ...

[bianchi77]

Re: Capacitor question ?

I have Atlas LCR45....it can show impedance....

[diif]

Re: Capacitor question ?

Yes I have one of those too. It doesn't measure ESR though. You need the ESR60 or ESR70 or one of those Chinese component testers that can come as a kit.

[bianchi77]

Re: Capacitor question ?

I've just bought :
http://www.aliexpress.com/item/New-H...08.0.92.XAgGCr

Is ESR60 from Atlas as well ?

[bianchi77]

Re: Capacitor question ?

Is it possible to test it in circuit ? or I need to desolder first ?

[diif]

Re: Capacitor question ?

My ERS70 seems quite accurate with the ESR on caps in circuit but will only measure capacitance about 50/50 depending on circuit layout. I haven't tried with my China tester as I need to make some leads.

[budm]

Re: Capacitor question ?

Is it possible to test it in circuit ? or I need to desolder first ?

Do the experiment, solder 4 caps with the same value and rating in parallel, then take the ESR reading, then figure out how to tell which one is the bad cap with high ESR.

[bianchi77]

Re: Capacitor question ?

ok, comparing between external soldered caps in parallel with in circuit one...got the idea...but I don't have ESR meter now

[budm]

Re: Capacitor question ?

ok, comparing between external soldered caps in parallel with in circuit one...got the idea...but I don't have ESR meter now

So you are comparing the whole SET (group) of cap to the same group of caps on the board, but how will you figure out which Cap/caps of the group on the board is bad if the reading of the group of the cap on the board read out higher. You have four caps in the group, but how can you tell which one is bad since they are connected in parallel?
All you can tell is that the two groups of the caps do not have the same reading, you still have to find which one of the 4 that causes the whole group to read wrong.
You can test the same theory with 4 1K resistors with same value in parallel, Rt = 250 Ohms, but if you have one of the resistor that has higher resistance (you can simulate by cutting one leg off, or have some one install 1M Ohms in its place and cover up all 4 resistor so you cannot tell which one is changed with 1M resistor) then the whole group will show higher resistance, so how do you tell which one of the four resistor has higher resistance than 1K that throw off the whole reading without cheating because you know ahead of time knowing that one of the resistor is no longer connected or changed out.

[bianchi77]

Re: Capacitor question ?

from the 4 resistors for example 100 100 100 100 in parallel....I will get 25 ohm eqivalent resistor....but one of the resistor change to 500 ohm.. it will increase the resistanse of course....but how can I decide which resistor is increasing ?
it will be in theory 1/R tot = 5/500 + 5/500 + 1/500 + 5/500 = 16 /500
R tot = 500 / 16 = 31.25 ohm....it's inceased, but which resistor becomes 500 ohms....?

How can I know which resistor is increased ?

for example there are C1 C2 C3 C4 and one or two Cs are faulty it will act as a resistor in circuit but how can I decide which C is faulty, except I desolder and test it on ESR meter one by one ?

[bianchi77]

Re: Capacitor question ?

If I chop the leg one by one, it's easier if I'm doing it outside the circuit...
but on PCB, it's the same thing, I desolder it, take it out all of them, test it on ESR and see what the response is.....I reckon that's the way I'll to test those caps for getting the exact result without guessing which one is faulty ?