Lytic voltage for replacement

[Electronicjoe]

I read somewhere that recapping with a higher voltage will not always succeed because the new cap may not "form" properly if it is rated much higher than the voltage it sees. Is this true? Can I use a 25 volt electrolytic in place of 10 volt?
Electronicjoe

[mockingbird]

Re: Lytic voltage for replacement

Nonsense. You can always use a higher voltage aluminum electrolytic cap. What does happen is that the etching in the foil conforms to the lower voltage if you run it for a while, so you can't use that cap in the future for its rated voltage.

[goontron]

Re: Lytic voltage for replacement

I read somewhere that recapping with a higher voltage will not always succeed because the new cap may not "form" properly if it is rated much higher than the voltage it sees. Is this true? Can I use a 25 volt electrolytic in place of 10 volt?
Electronicjoe

yeah, if they have been sitting for 50 years like in the tube radios i work on. then otherwise, no.

have you been on the audiokarma site? that sounds like (mis)info you hear there.

[momaka]

Re: Lytic voltage for replacement

What does happen is that the etching in the foil conforms to the lower voltage if you run it for a while, so you can't use that cap in the future for its rated voltage.

Actually, you can. However, you must "reform" the cap first.

First find a power supply that has an output voltage as close as possible to the capacitor's rated voltage (but not higher). Then using a 1 KOhm resistor or higher (10k is a little safer, but the process is slower), hook the capacitor in series with the resistor and connect to the power supply. Let it sit like that for a while. In my experience, 1 hour is more than enough. Some caps will reform (adequately, but not fully) within 5-10 minutes.

I often do this when I re-use motherboard capacitors (when I remember, that is ).