High ESR capacitors

When electrolytic capacitors age, many changes can take place:

• drift in capacitance
• increase in ESR
• increase in leakage current
• open circuit
• short circuit

High ESR is a common problem. It is easy to test for this without removing the capacitor in question. Connect a good capacitor in parallel with the capacitor in question. If the problem goes away, the original capacitor is probably bad due to high ESR and/or reduced capacitance.