From: et472@ncf.ca   
      
   On Sat, 29 Mar 2014, Trevor Wilson wrote:   
      
   > On 29/03/2014 10:32 AM, Trevor Wilson wrote:   
   >> On 13/02/2014 7:57 PM, Sainthunter wrote:   
   >>> I recently bought a Denon 'Personal Component System/AM-FM Stereo   
   >>> Receiver DRA-F100' unit from a charity shop - sold for spares or repair.   
   >>> Apart from a tuner issue the main fault is that after a while in standby   
   >>> mode it switches off completely from standby as though the mains has   
   >>> been switched off/a power cut.   
   >>> Is there a back-up memory battery somewhere, I have tried leaving the   
   >>> unit powered up and switched on for at least 24 hours kidding myself   
   >>> that it will recharge the memory battery, if there is one?   
   >>>   
   >>   
   >> **I don't have the service manual for that model, but most machines of   
   >> that vintage use a large, low leakage electrolytic cap of approximately   
   >> 20,000uF @ 6.3Volts. It will likely be near the main microprocessor.   
   >>   
   >>   
   >   
   > **BTW: By "large", I mean in capacity. The physical size is likely to be   
   > approximately 20 ~ 25mm high and 15mm in diameter.It may also use a   
   > 'supercap', which could be in the range of 0.1F ~ 1F @ 5.5 Volts, but I doubt   
   > it.   
   >   
   That's a good point.  I remember the cartoons in hobby magazines about   
   what a Farad capacitor would look like, usually the single unit delivered   
   ont he back of a truck.   
      
   If such large capacitors existed, they sure weren't at the hobby or   
   consumer level forty years ago.  I remember buying a 'computer grade"   
   electrolytic, the size of a Coke can, 15,000uF at about 16V.  Barely high   
   enough voltage rating for my purposes, but it was what I could get   
   surplus.   
      
   Now you can get even higher capacitance electrolytics in a much smaller   
   package.   
      
   ANd yes, by physical size, you'd never grasp that those backup capacitors   
   in more recent equipment had such large capacitance values.   
      
      Michael   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)