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.
Modern electrolytic capacitors are available in a wide variety of ratings and shapes. Replacing old electrolytic capacitors with new ones is a straightforward procedure. Just make sure that the new one can fit, mechanically.
Old devices shall repeatedly powered on from time to time, to hold the old elektrolytic formed. If this is not done, the forming current at power up may be extremely high an the elco or the rectifier tube may be demaged. Old devices from Ham shall be slowly started up with a variac, within some minutes.