From: liz@poppyrecords.invalid.invalid   
      
   Cursitor Doom  wrote:   
      
   [...]CD.   
   >   
   > PS: the aforementioned caps are 47000uF 16V Vishay ones - and I have a   
   > brand new spare that's also testing as "leaky"!   
      
   If an electrolytic capacitor hasn't been used for some time, it is a   
   good idea to charge it up from a variable-voltage power supply, starting   
   at a very low voltage with an ammeter in series.  If it is leaky the   
   initial charging current surge will settle down to a steady leakage   
   which will decrease in time.  Then the voltage can be raised a bit and   
   the leakage current will increase for a while, then reduce again.   
      
   By doing this slowly over several hours you re-form the insulating layer   
   in the capacitor.  If you apply the full voltage straight away, the   
   leakage current will be high and can cause further damage.  It can also   
   boil the electrolyte and cause the capacitor to explode.  Modern   
   capacitors have a 'safe' explosion arrangment built-in (a pattern of   
   weak points in the top of the casing) but older ones don't - and the   
   damage from flying debris can be quite spectacular (I have seen a CRT   
   cut in half when a capacitor can went through it).   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
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