[Coco] Powering up our retro systems

Dave Philipsen dave at davebiz.com
Mon Jan 27 08:35:42 EST 2020

Sent from my iPhone

> On Jan 27, 2020, at 6:57 AM, 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. 

>  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.   

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. 

>  But that's just me.
>   Good luck.
>   Will
>   References
>   1. mailto: [2]dave at davebiz.com
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> References
>   1. mailto:dave at davebiz.com
>   2. mailto:dave at davebiz.com
>   3. mailto:Coco at maltedmedia.com
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