I have only just noticed this thread as a result of it being posted to recently.
I thought ESR is the same thing in wax paper as it is in electrolytics, the effective difference being that in electrolytics it is more noticeable because the capacitive values are higher, this coupled with them needing to be reformed will give a very high ESR value.
The cause of a high ESR will, be as already mentioned, allow DC current to flow through the capacitor even after it is charged.
With small value wax paper caps in very high impedance circuits such as the grid coupling capacitor this can be critical even though the actual current may be miniscule. With large electrolytic capacitors in the HT smoothing circuits the ESR of a capacitor that is failing can cause very significant DC currents to flow and have been known to damage rectifiers, speaker energising coils and mains transformer secondaries.
One additional comment I would make is I have often found modern electrolytics to have very poor ESR values and sometimes the 50 year old ones show a lower ESR.
Regarding the Bush TR82C see my comment on your introduction thread.
Mike
I thought ESR is the same thing in wax paper as it is in electrolytics, the effective difference being that in electrolytics it is more noticeable because the capacitive values are higher, this coupled with them needing to be reformed will give a very high ESR value.
The cause of a high ESR will, be as already mentioned, allow DC current to flow through the capacitor even after it is charged.
With small value wax paper caps in very high impedance circuits such as the grid coupling capacitor this can be critical even though the actual current may be miniscule. With large electrolytic capacitors in the HT smoothing circuits the ESR of a capacitor that is failing can cause very significant DC currents to flow and have been known to damage rectifiers, speaker energising coils and mains transformer secondaries.
One additional comment I would make is I have often found modern electrolytics to have very poor ESR values and sometimes the 50 year old ones show a lower ESR.
Regarding the Bush TR82C see my comment on your introduction thread.
Mike
