Identifying failed polymer-based capacitors

[blackness]

I have a problem with a PC that does not start and there are several likely culprits, including motherboard and PSU. One way of looking for faults is to look for faulty or leaky capacitators, if they contain liquid electrolyte. However, all capacitors on these components are polymer-based (as far as I can see). Is there any way one can identify a failed polymer-based capacitor? I have been looking all over the net whithout finding clear advise on this, so any feedback would be much appreciated. Thanks

The system in question:
Asrock X79 Extreme6, 64 GB, 1066, 1333, 1600, 1866, 2133, 2400 MHz, DDR3-SDRAM, quad, Intel, LGA2011 mainboard
Sapphire R9 280 Dual-X OC 3GB GDDR5 graphics card
Intel Socket 2011 - Intel Core I7-3820 3.60Ghz Box Socket 2011
Noctua NH-D14 SE2011 cooling
Corsair CMPSU-700G, 700 W, power
32 Gb memory
Be Quiet Shadow Wings 120mm 2200rpm fan
Win 7

 

[Someone Somewhere]

Polymer-based caps fail VERY rarely. They can still bulge and even explode upon failure, but note that for both polymer and electrolytic caps, failure is not always visible.

The only way to tell 100% is to desolder and remove the caps, then test with a multimeter. Even then, unless you have something to measure ESR, it's not certain.

I would bet on it not being a polymer cap that has failed.

I suggest going through our guide, if you haven't already: http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

[Pinhedd]

Polymer-based caps fail VERY rarely. They can still bulge and even explode upon failure, but note that for both polymer and electrolytic caps, failure is not always visible.

The only way to tell 100% is to desolder and remove the caps, then test with a multimeter. Even then, unless you have something to measure ESR, it's not certain.

I would bet on it not being a polymer cap that has failed.

I suggest going through our guide, if you haven't already: http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

A multi-meter is not sufficient to test for a failed cap that may be affecting a motherboard. A very expensive impedance tester is needed

 

[Someone Somewhere]

Imdedence ~ ESR. I'd say ESR is the more accurate term, given that impedance includes reactance, which isn't what we're after in this case.

 

[Pinhedd]

Imdedence ~ ESR. I'd say ESR is the more accurate term, given that impedance includes reactance, which isn't what we're after in this case.

Impedance is the vector sum of resistance and reactance on the complex plane. ESR is the resistive component of a nominally reactive device (such as a capacitor) which is a consequence of perfectly reactive devices being damn near impossible to realize without superconducting material. Ideal capacitors have no ESR.

In any case, ESR and capacitance can't be measured using a basic multimeter. The capacitor will charge and current flow will drop until it becomes an open circuit from the perspective of the multimeter. Some high end Fluke multimeters can perform basic ESR and capacitance measurements but those multimeters are extremely expensive and are still inferior to a good benchtop impedance tester.

 

[Someone Somewhere]

I have pretty easy access to two multimeters. Both can measure capacitance. One is pretty cheap and nothing amazing.

ESR and impedance can be calculated from each other, given the frequency and capacitance are known.

I was mainly alluding to the fact that it is possible for a capacitor to fail (or at least become less effective) without the capacitance changing. ESR is generally the value marketed and specified for caps, so the OP may be more familiar with that than impedance.

The only time I can see impedence being more important to measure than ESR would be at very high frequencies where the inductance of the capacitor comes into effect - never going to happen in most circumstances.

 

[blackness]

Polymer-based caps fail VERY rarely. They can still bulge and even explode upon failure, but note that for both polymer and electrolytic caps, failure is not always visible.

The only way to tell 100% is to desolder and remove the caps, then test with a multimeter. Even then, unless you have something to measure ESR, it's not certain.

I would bet on it not being a polymer cap that has failed.

I suggest going through our guide, if you haven't already: http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

Good tip. Basic guide, but thorough. Thanks.