[sdiy] The life and death of a Phonic power conditioner

Rutger Vlek rutgervlek at gmail.com
Sat Jan 28 14:22:57 CET 2017

By the way, this may be one of the few situations where a capacitor dropper
supply makes sense: mains voltage monitoring. The scope seems to have
survive the current through its ground, tough the traces seem skewed since
the incident. Possibly a cap that took a transient  part of the blow.


Op 28 jan. 2017 13:42 schreef "Rutger Vlek" <rutgervlek at gmail.com>:

Thanks Richie, good advice. I'll let this project wait for another moment.


Op 28 jan. 2017 13:04 schreef "Richie Burnett" <rburnett at richieburnett.co.uk

However... I thought, let's check if the recto before it is working
>> correctly. I thought I'd be able to see this with my scope on the waveshape
>> easily, and connected the scope's ground terminal to the circuits local
>> ground (the negative side of C4) and boom! Big explosion! Fried part of my
>> scope's ground clamp...
> Capacitor dropper power supplies are dangerous to work on.  Always use a
> mains isolation transformer when doing this type of repair work.  Never be
> tempted to float the ground connection to the scope, that's how fatalities
> happen.
> Also... I was expecting this circuit to behave such that the local ground
>> would adapt to any other ground applied to it.
> Yep, don't clip scope probe grounds onto anything that might be mains
> live. If in doubt probe it with a DVM first.
> And finally.... why would a big (film, not elco!) cap get fried way below
>> it's operating voltage of 400V...
> You most likely exceeded it's peak current rating when you shorted one
> side of it to ground, resulting in vaporisation of the thin metal foil, or
> failure of a weak point where the ends of the foil plates are connected to
> the component lead.
> Or is that a DC voltage rating?
> Will be the max DC voltage rating.
> And finally, why is my flu still not gone! (perhaps that explains it
>> all...wait before repairs until you're recovered?)
> I think lots of people who've been ill over Christmas/New year are still
> puzzling over that one.  (Seriously though, work on something low-voltage,
> or write some code, but don't probe around live mains powered equipment
> when you're not at your most alert!  Fortunately you didn't get bitten, or
> get anything in your eye from the unexpected component explosion.  Damaged
> scopes and power bars can be replaced.)
> -Richie,
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