Reliability of unused electrolytic capacitors?

During the COVID-19 shutdown I’ve been trying to tidy up the work bench. I have quite a few electrolytic capacitors that are intended for mounting on PC boards. They have been stored at room temperature, but I have no idea how old they are – easily could be 10 years or more. I know that the electrolyte in these capacitors eventually evaporates, a process hastened by heating when the capacitor is in a circuit. These capacitors have never been used. If such a capacitor shows the appropriate capacitance on a C-meter, can it be trusted? Or should I simply discard them as being unreliable because of their age?

Tks & 73,
Scott WB8ICQ

If they are high voltage capacitors you should reform them. Loads of info online, Google “reforming electrolytic”.

Quite right Andy. That should also be done to lower voltage types.
Capacitance alone is not enough to know whether to keep or bin. You need to measure the ESR.
Of course Scott as you haven’t used them in a decade you probably should give them to someone who can use them. Historical radio society?


It’s normally less likely to be a problem with lower voltages unless they are being stressed such as smoothing caps in a linear psu. But yes, a reform is probably worth doing.

I need to have a big clearout of the HV valve parts that are never going to get pressed into service here. It’s now easy and quite affordable to exceed the 1kW power level using solid state devices even if you need to find 50V at big Amps to power it. At one of my contest group’s last outings where we were QRO on 2m the setup of the 2m LDMOS amp was simplicity, take it out its box, connect the lead from the IC970, connect the flexible QRO patch lead (about 2m) from the PA to the incoming LDF-450 from the antennas, connect the 3.5mm PTT lead to the 970, plug the IEC mains lead in, hit the power switch, wait for the amp to self test and the standby light to come on, drive level to 0, PTT on, adjust drive level to give power and check SWR OK. Took about 5mins. Even key down, the fans move air at low pressure over the heatsinks and the noise is barely perceptible. In comparison, assembling and setting up the 3cx800 based amp takes about 90mins. I missed the row from the centrifugal blower for all of about 10secs.