caps ?

[Jim GM4 DHJ ...]

with regard to caps in an old radio is it better to keep a radio switched on or switched off or is degradation just age dependant?

[jon]

Presumably 'Electros' is Australian shorthand for Electrolytic Capacitors.

[Harry Bloomfield, Esq.]

Switched on! Left off for years, old capacitors can form a short. The usual way is to reform old capacitors by gradually increasing the voltage across them over a period of time, but that doesn't always work.

[Fredxx]

They can dry out when left on. Electrolytics are specified for running time, at voltage, at a temperature. Shelf life is much, much longer.

They are best unused but turned on occasionally to reform their dielectric layer.

A term rarely used. The word 'lytics' is far more common.

This might assist for an English speaking person posting on a UK newsgroup:

[Jim GM4 DHJ ...]

thanks

[Radio Man]

Old paper caps dry out and fail short.

With Electrolytics, one of the plates is formed by the electrolyte and dissipates over time. As Harry says, you can sometimes reform the plate by slowly increasing the applied voltage. More of an issue with high voltage equipment and situations where the current isn?t limited.

On modern kit, including lower voltage stuff, leakage of electrolyte is an issue. It isn?t unusual to see fluid/jelly leaking from capacitors- often with bulging bodies. While they may still work after a fashion, they should be replaced.

[Peter Parry]

Paper and moulded paper fail with age no matter what you do with them. Some old electrolytic (especially the physically large ones seem to survive for longer than expected but will fail whether left on or not.

If you are renovating something it is usually wise to replace all paper and electrolytic capacitors.

[Andrew]

All valve equipment should be left on - assuming you aren't paying the leccy bill.

[tabbypurr]

If left on 24/7, the valves will lose emission & the electrolytics will expire. If off all the time, the electrolytics will short when powered up. Whoever said leave it off but power it up on occasion is right as far as extending its life goes /if repair is excluded/.

But the caps are in almost all valve radios now shot, and powering up such things can easily do damage. Better to check all the caps & replace where needed.

NT

[Brian Gaff (Sofa]

Yes and some just dry out either way it seems. When powering up a radio after a long time not running ie a valve one, do it via a light bulb first as sudden full volts can create a terrible mess if a cap goes bang and spreads nasty smelling gunk and bits of paper all over the innards of the cabinet. I made this mistake with an early TV once, a view, yes they really called it that, with a 9 in screen and a humungous cabinet full of valves. Brian

[Brian Gaff (Sofa]

Yes especially when my spell checker does not know how to spell it either. Brian