a 20mfd to replace a 18mfd electrolytic capacitor? I can't find anyone who has the 18.

In 99% of applications, this is the correct choice. Most electrolytic capacitors have a fairly wide tolerance range, especially on the up-side. A cap marked 20 mfd might easily be 22 or 24 mfd. If this is for a filter in a vintage radio, the higher capacitance is no problem.

Rich

:a 20mfd to replace a 18mfd electrolytic capacitor? I can't find anyone who has the 18.

For a good treatise on re-capping old radios, try:

http://www.antiqueradio.com/Dec04_Cantelon_capacitor.html

73... Rich

:In 99% of applications, this is the correct choice. Most electrolytic capacitors have a fairly wide tolerance range, especially on the up-side. A cap marked 20 mfd might easily be 22 or 24 mfd. If this is for a filter in a vintage radio, the higher capacitance is no problem.
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:Rich
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::a 20mfd to replace a 18mfd electrolytic capacitor? I can't find anyone who has the 18.