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I've managed to blow a capacitor while doing maintenance on my 1967 electric organ. It's a 80uf 25V. I've done some searching and found that I can replace it with one that has a higher voltage rating but the same farad value. Is there anything else that I need to know before I buy a replacement? I've read some things about ripple current and resistance? The numbers on the capacitor are: B41283-s5806-z2 80uf 25V A 0-507-24 W9

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Very likely any 80 µF capacitor you can find today rated at 25 V or more will work fine in this situation. Such a capacitor from 1967 is electrolytic, so already polarized. Replacing it with a 80 µF 35 V, for example, modern capacitor should no result in any problems.

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    \$\begingroup\$ EE in training, here. Isn't it true that electrolytic perform better around their rated voltage? So he should go with a 25V? \$\endgroup\$ Jan 28 '17 at 22:48
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    \$\begingroup\$ no always better to have at least 20% margin higher V ratings also tend to have lower ESR \$\endgroup\$ Jan 28 '17 at 22:56
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    \$\begingroup\$ @BrianDohler, I remember being told that electrolytics should have at least 10% of rated voltage across them but I couldn't find much to back that up when I once read around. So I'd say putting a 35V in should be fine. \$\endgroup\$
    – TonyM
    Jan 28 '17 at 22:59
  • \$\begingroup\$ Thanks guys. I'm not sure where I heard that and I couldn't find anything to back it up either. \$\endgroup\$ Jan 28 '17 at 23:04
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    \$\begingroup\$ @TonyM: There is some truth to what you say. Keeping some voltage on electrolytics helps preserve the oxide layer that is the dielectric. It's not much of a issue with modern capacitors, though. I only mentioned 35 V since that's a common voltage today. I would expect a 25 V cap to already be derated properly in the original design. Changing from 25 to 35 V really shouldn't be any issue. It's not a large change \$\endgroup\$ Jan 28 '17 at 23:50
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A 80µF electrolytic capacitor from 1967 could be easily 120uF back then, and 40µF today. It probably had a much higher internal resistance than modern capacitors. I think any good quality 100µF 25V is okay. You may of course use 100µF 35V or higher voltage. If you still prefer 80µF, that is okay, but I really think that 80µF or 100µF does not matter.

Do you know how old tube radios are repaired ? Every capacitor is cut away and replaced, without testing them if they are bad or still a little okay.

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  • \$\begingroup\$ Not just tube radios. This is standard procedure for vintage valve hifi. \$\endgroup\$
    – user207421
    Jan 29 '17 at 13:41

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