Re-forming electrolytic capacitors.

[PaulR]

I used to do the minimum to repair the set in order to preserve originality but having had sets fail again quite quickly after that I tend to replace all the sensitive capacitors.

Having got my power supply I have found that if electrolytics will reform then they tend to be quite reliable and I now try to keep these.

[stuarth]

Is capacitor re-forming a good use for a low impedance voltmeter such as an AVO7.

If you just wire the meter on a high VOLTAGE range in series with the HT supply to the capacitor, it will safely limit the current (I use a Siemens Multizet S, a 1kohm/volt meter, so 1mA fsd) and show leakage current flowing in the capacitor.

It can be safely be left unattended because the maximum dissipation in the capacitor will be in the scores of mW, even if the capacitor unexpectedly goes low resistance.

You don't need current limited power supplies - you can just use the set's own supply, or pinch a milliamp from any other convenient source of appropriate HT voltage.

S

[G8HQP Dave]

The snag with that is that a good electrolytic might take nearly a mA in leakage current. It will work for some caps which end up at very low leakage after reforming, but not for those which happen to have high leakage even when healthy.

[samjmann]

Hi all,

Thanks to everyone that replied to my opening question. As ever on this forum replies are knowledgeable, informative and interesting. As engineers we all have our own way of doing things, hence there isn't always an absolute right or wrong way of doing this - circumstances dictate!

I've got an isolated variac, so I'll make up a simple current limited supply to run the Leak's capacitors up for the first time; keeping an eye on the current drawn!

Regards, SJM.