Electrolytic capacitors - Page 2

bigwill · 16th August 2009, 12:41 PM

Quote:

Originally posted by MellowTone
So essentially, any electrolytics made pre-1991 should pretty much be thrown and replaced?

I hope not. I have a box of NOS 450v electrolytics that would be a shame to throw away, especially if I can reform them

RocketScientist · 16th August 2009, 03:18 PM

If you can reform old caps, get the leakage current within spec, and verify the capacitance value, they might be OK for some applications--for a while. But other parameters are likely to still be degraded like ESR, dissipation factor, etc. And they may not last much longer--especially if used near their rated voltage, at high temperatures, or with high values of ripple current.

For example, the electrolytics used on most PC motherboards for the switching regulator near the CPU, are famous for failing after only 3 or 4 years. And even before they fail, their parameters are degraded enough the PC often starts to have problems because of unstable power. But those caps live in a hot environment with high amounts of ripple current. Newer high-end motherboards are using polymer caps to avoid the early failures with electrolytics.

star882 · 16th August 2009, 04:27 PM

Just connect it to a power supply at about the rated voltage with current limiting such that it would take hours to days to fully charge. Then just leave it for longer than that.

bigwill · 16th August 2009, 05:13 PM

Thanks for the advice guys.

I will probably just reform them with the techniques given and use them in my own equipment. I won't use them when repairing other peoples'

16th August 2009, 04:27 PM	#13
star882 diyAudio Member Join Date: Mar 2007	Just connect it to a power supply at about the rated voltage with current limiting such that it would take hours to days to fully charge. Then just leave it for longer than that. __________________ "Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!

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16th August 2009, 03:18 PM	#12
RocketScientist diyAudio Member Join Date: Mar 2008 Location: Northwest	If you can reform old caps, get the leakage current within spec, and verify the capacitance value, they might be OK for some applications--for a while. But other parameters are likely to still be degraded like ESR, dissipation factor, etc. And they may not last much longer--especially if used near their rated voltage, at high temperatures, or with high values of ripple current. For example, the electrolytics used on most PC motherboards for the switching regulator near the CPU, are famous for failing after only 3 or 4 years. And even before they fail, their parameters are degraded enough the PC often starts to have problems because of unstable power. But those caps live in a hot environment with high amounts of ripple current. Newer high-end motherboards are using polymer caps to avoid the early failures with electrolytics.

16th August 2009, 05:13 PM	#14
bigwill General Nuisance diyAudio Member Join Date: Dec 2004 Location: UK	Thanks for the advice guys. I will probably just reform them with the techniques given and use them in my own equipment. I won't use them when repairing other peoples'