How to test old capacitors?

[SylvainP]

Hello all.

Due to putting the hobby aside for a few decades I have lots of old capacitors. I wonder how I should test them, is measuring their value with a cheap capacitance meter enough?
I mostly have ceramics and electrolytics.  I ordered an LCR meter recently if that helps (a DER EE DE-5000), I should receive it in a few weeks.

[retrolefty]

 Older larger electrolytic caps seem to have most trouble with old man time and heat aversion. People that restore the real old stuff (think vacuum tube equipment) will take time to 'reform' the old electrolytic at low voltage before applying full power to a piece of equipment.

 After that normal capacitance and ESR measurement should do a good job of checking their condition. Most small non-electrolytics caps are pretty reliable and should only require specific checking if higher level troubleshooting leads one to suspect one.

[Fraser]

My personal view.... Bin the electrolytic if they are more than around 5 years old. No issues with ceramic, polyester, Mica or polyester capacitors as long as they have been kept dry.

I don't waste time with poor quality or elderly electrolytic capacitors as the grit a dud could cause outweighs the cost of buying a selection of fresh stock values.

Aurora

[rdl]

I always thought that decent quality electrolytics would last quite a long time when stored somewhere near normal room temperature. I frequently use Panasonic electrolytics that were bought in the 80s and they seem to work as expected.

[Fraser]

Electrolytic capacitors are sealed with a rubber membrane. It all comes down to how much you trust the membrane to hold up over time. I personally would not install a 1980's capacitor in a unit during repair or for important prototyping. Hobbyists can likely take a risk on non critical projects.

If an old Electrolytic capacitor is installed in a piece of important equipment, how long will it last before the cap needs changing again ? Every time you change the capacitor, you thermally  stress the PCB track adhesive. A PCB is always worth more than a decent capacitor. Why take the risk with such a low cost component ?

Aurora