From: liz@poppyrecords.invalid.invalid   
      
   Cursitor Doom  wrote:   
      
   > On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid   
   > (Liz Tuddenham) wrote:   
   >   
   > >Cursitor Doom  wrote:   
   > >   
   > >> On Sun, 25 Feb 2024 19:40:48 +0100, HW  wrote:   
   > >>   
   > >> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom    
   > >> >wrote:   
   > >> >   
   > >> >>So - in the case of a linear power supply - the rectified output of   
   > >> >>the transformer typically goes straight to a big old storage cap for   
   > >> >>smoothing purposes. My question is: how much ripple should I expect to   
   > >> >>see across that cap if all's working well? I have to say I'm seeing a   
   > >> >>*lot* of ripple on this cap   
   > >> >   
   > >> >Check if a diode in the bridge rectifier has failed.   
   > >>   
   > >> Good idea! I must admit I'd overlooked that possibility. I should have   
   > >> checked the frequeny of the ripple whilst I was at it.   
   > >   
   > >The shape of the ripple will tell you if that has happened or if one of   
   > >the diodes haas gone open circuit.  Another possibility is a fault in   
   > >some other part of the circuit that is drawing too much current - you   
   > >might smell something getting hot.   
   >   
   > There's nothing getting hot, but the ripple had a definite saw-tooth   
   > shape to it, which could be indicative of abnormal operation.   
   > Shame there are no schematics available anywhere on the net; always   
   > makes troubleshooting much harder.   
      
   Is the rectifier circuit half-wave or full-wave?  If the latter, is the   
   ripple also full wave?   
      
   Some designers allowed a larger amount of ripple on the first capacitor   
   to reduce the heating of the mains transformer (the copper losses are   
   proportional to I squared, so by allowing a longer charging time per   
   cycle at a lower current, they achieved lower overall resistance   
   losses).  As long as the lowest part of the ripple was sufficiently far   
   above the stabilised output, a series stabiliser could cope with it.   
      
   Is the 'stabilised' line actually stable or is there ripple on it in the   
   form of a series of little notches?   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)