[Coco] Powering up our retro systems

[wrcooke at wrcooke.net]

   On January 27, 2020 at 7:35 AM Dave Philipsen < [1]dave at davebiz.com>
   wrote:

   Sent from my iPhone

   On Jan 27, 2020, at 6:57 AM, [2]wrcooke at wrcooke.net wrote:

   To each his own. My experience is different. The experience of other

   people I've known / talked to, as well as videos I've seen, is also

   different. A shorted cap will draw max current from a transformer,

   limited only by the inherent resistance of the transformer/rectifier

   combination. It doesn't take long of ten amps through a two amp

   transformer to burn it out.

   I’m not sure I understand how a transformer as small as the one in the
   CoCo is going to be pushing ten amps of current through a shorted cap.
   Every device I have ever repaired with bad/leaky caps sustained no
   damage to other power supply components as a result of the shorted cap.

   Ohm's law: I = E/R

   A typical small transformer, say 12V/ 2A, will have a winding
   resistance around 1 Ohm.  12V/ 1 Ohm = 12 amps

   A "deformed" cap is not the same as a "bad" cap.

   I personally prefer to use a bit of

   precaution up front rather than try to source an identical custom

   transformer that hasn't been made in 30 years.

   But even if you try to “reform“ the caps on a regular basis, the time
   will still come when you turn on the computer and the cap(s) have
   failed and you will have strained the transformer. Electrolytic
   capacitor failure is not *if* they fail, it’s *when* they fail.

   True.  But the life will be much longer.

   I also believe that the hardest thing on a cap is not sitting without
   being used for a long period of time, it is being exposed to high
   temperatures. I have witnessed many, many more failures of electrolytic
   caps in old tube designs where the heat of the tubes in the enclosure
   was likely the killer of the cap.

   Modern caps are MUCH different than the old ones used in tube radios.
   They rarely dry out.  The manufacturers continuously improve them.  But
   even the newest ones WILL fail eventually for some reason.

   This document:
   [3]https://www.tdk-electronics.tdk.com/download/530704/6ad5ed9e1ff4f727
   c328cb92da2adf2b/pdf-generaltechnicalinformation.pdf

   From TDK, a reputable manufacturer of electrolytic caps, has a great
   deal to say about the life and storage of them.  It specifically says
   they are expected to be reformed after storage.  See sections 3.7.7 and
   7.3

   Best,

   Will

   But that's just me.

   Good luck.

   Will

   References

   1. mailto: [2] [4]dave at davebiz.com

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   [3] [5]Coco at maltedmedia.com

   [4] [6]https://pairlist5.pair.net/mailman/listinfo/coco

   "A designer knows he has achieved perfection not when there is nothing

   left to add, but when there is nothing left to take away." -- Antoine

   de Saint-Exupery

   "The names of global variables should start with // "

   -- [7]https://isocpp.org

   References

   1. mailto: [8]dave at davebiz.com

   2. mailto: [9]dave at davebiz.com

   3. mailto: [10]Coco at maltedmedia.com

   4. [11]https://pairlist5.pair.net/mailman/listinfo/coco

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   Coco mailing list

   [12]Coco at maltedmedia.com

   [13]https://pairlist5.pair.net/mailman/listinfo/coco

   --

   Coco mailing list

   [14]Coco at maltedmedia.com

   [15]https://pairlist5.pair.net/mailman/listinfo/coco

   "A designer knows he has achieved perfection not when there is nothing
   left to add, but when there is nothing left to take away." --  Antoine
   de Saint-Exupery

   "The names of global variables should start with    // "
   -- https://isocpp.org

References

   1. mailto:dave at davebiz.com
   2. mailto:wrcooke at wrcooke.net
   3. https://www.tdk-electronics.tdk.com/download/530704/6ad5ed9e1ff4f727c328cb92da2adf2b/pdf-generaltechnicalinformation.pdf
   4. mailto:dave at davebiz.com
   5. mailto:Coco at maltedmedia.com
   6. https://pairlist5.pair.net/mailman/listinfo/coco
   7. https://isocpp.org/
   8. mailto:dave at davebiz.com
   9. mailto:dave at davebiz.com
  10. mailto:Coco at maltedmedia.com
  11. https://pairlist5.pair.net/mailman/listinfo/coco
  12. mailto:Coco at maltedmedia.com
  13. https://pairlist5.pair.net/mailman/listinfo/coco
  14. mailto:Coco at maltedmedia.com
  15. https://pairlist5.pair.net/mailman/listinfo/coco