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reforming electrolytic capacitors
reforming electrolytic capacitors
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Old 17th April 2018, 01:54 AM   #61
TonyTecson is offline TonyTecson  Philippines
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reforming electrolytic capacitors
Quote:
Originally Posted by audiostrat View Post
Many thanks for the answer. But it still bothers me, why is it allowed to charge a capacitor way beyond (maybe) its rated voltage, but usually caps have a specified surge voltage?

Is it because the surge is specified during a switching load condition? So that the combination of heat + surge would destroy the cap, whereas in a slow, static environment (like a 10k in series) the capacitor can take bigger voltages?
in service, where impedances of the traffo is very low, it is good practice to never allow terminal voltages exceed the rated voltage of the cap, surge voltage are short duration events that should never be allowed to happen at all f you want your caps to last...

testing with high impedance sources as in "reforming" is a different ball game...
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Old 17th May 2018, 04:12 PM   #62
audiostrat is offline audiostrat  Greece
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Default Reform time!

For the record, I am reforming these KMH 10,000uF 63V Nippon capacitors today, following the guideline of the manufacturer - that is, to charge them in 63V through 1k resistor.

I built an LM317 63V regulator on a breadboard, and connected the caps to that output using a 1k, 5W resistor for each one.

They immediately charged up to 60V and 58.9V, and after 5 minutes, they had reached 62.6V. I plan to leave them for 24 hours and then remove them.

If I am correct, the caps seem to be doing very good! Less than 0.4 mA leakage in 5 minutes is encouraging, I think.

Which gives credit to Tony for assuming that these caps did not need reforming at all, but it's the first time I attempt it so I gave it a go.

The caps are indeed less than 4 years old: (codes on post #50)
45aP4M = 27 May 2014
54WP1M= 23 April 2015

These dates conform with this document that can be found online.

Update: 50uA leakage reached in 20 minutes (reached 62.73V while the LM317 output is 62.78V).

Last edited by audiostrat; 17th May 2018 at 04:18 PM.
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Old 17th May 2018, 10:23 PM   #63
TonyTecson is offline TonyTecson  Philippines
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reforming electrolytic capacitors
that is good.....discharge that cap and short the terminals if not using immediately after reforming...
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Old 19th May 2018, 04:52 PM   #64
Andersonix is offline Andersonix  Sweden
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reforming electrolytic capacitors
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Originally Posted by TonyTecson View Post

when reforming a 63v cap say, then a voltage source higher, say 100 volts is needed and a 10k 5 watt resistor is added....
This statement on its own is irresponsible and could lead an inattentive cap reformer to blow up the cap with too high voltage.
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Old 21st May 2018, 10:15 PM   #65
Lingwendil is offline Lingwendil  United States
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reforming electrolytic capacitors
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Originally Posted by Andersonix View Post
This statement on its own is irresponsible and could lead an inattentive cap reformer to blow up the cap with too high voltage.
Yeah, please don't do this unless you have some sort of overvoltage protection. A simple Zener across the cap will suffice, sufficiently rated, of course.
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