0
\$\begingroup\$

I have two SMD capacitors (33pF and 1nF) that I pulled out from a faulty graphics card.

I measured the resistance of both. They didn't have any resistance (O.L,) but they not shorted.

When I switched to diode mode I got the same result.

I can measure of the capacitance and they have the correct values.

Are these two capacitors still good? I’am quite new to electrical enginering, so apologize if this is an odd question.

\$\endgroup\$
3
  • \$\begingroup\$ What job do these perform, what ESR and SRF do you expect? Why did you remove them? These types have low failure rate. Did you want to measure the RLC characteristics? \$\endgroup\$ Jan 9, 2022 at 17:45
  • \$\begingroup\$ @tony stewart EE75 i’ve been troubleshooting gpu that missing voltage at memory rail. And i look at pwm controller (APW7165C) its missing voltage at ENABLE signal. And that signal is connected to this two caps and one 15k ohm resistor. The resistor In the correct value btw. Thats why i pulled out this two caps to make sure this not faulty \$\endgroup\$ Jan 9, 2022 at 18:24
  • 4
    \$\begingroup\$ They didn't have any resistance (O.L,) ... that is a very large resistance ... zero ohms is no resistance \$\endgroup\$
    – jsotola
    Jan 9, 2022 at 18:53

2 Answers 2

4
\$\begingroup\$

If you measure a capacitor on resistance mode and read anything other than overload, that's an indicator that the capacitor is bad. A working capacitor will read very high resistance, higher than most multimeters can measure.


Note that there is one resistive figure of merit that is useful for determining whether a capacitor is dead or not. This is the capacitor's ESR (Equivalent Series Resistance), which might be what you were trying to measure here. But you can't measure ESR with a normal multimeter; you need a specialized meter for that. There are dedicated ESR meters, but most LCR meters can also measure capacitors' ESR.

The ESR of specifically an aluminum electrolytic capacitor (the ones in little cylindrical metal cans) tends to increase when the capacitor is near end-of-life, and capacitors with abnormally high ESR should be replaced. Failure of ceramic and film capacitors, as well as tantalum electrolytics and aluminum-polymer caps, can't be predicted in the same way, although (with the exception of tantalum capacitors) these don't have the same propensity to fail with age as standard aluminum capacitors.

\$\endgroup\$
3
  • \$\begingroup\$ When first test i can see some value then it switch to O.L. Seems matched on your answer. Thanks \$\endgroup\$ Jan 9, 2022 at 17:05
  • 1
    \$\begingroup\$ Yes, some current will initially flow until the capacitor charges and then stops when fully charged. Assuming your meter supplies a constant current for ohm measurement, the voltage across the cap will increase linearly to the maximum voltage of your meter allowed on ohm setting. Higher value capacitors take longer to come to the steady state. \$\endgroup\$ Jan 9, 2022 at 17:49
  • 2
    \$\begingroup\$ @AndrewMorton I've seen people say both, but my meter says OL when the measurement is out of range on a voltage or current range too, so "overload" makes more sense to me. Particularly when you put it on conductance mode and it says OL when you short the leads! \$\endgroup\$
    – Hearth
    Jan 9, 2022 at 18:05
2
\$\begingroup\$

Capacitors should not have any DC continuity. Your caps seem fine per your tests.

\$\endgroup\$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.