Leaky Capacitor

Not so long as the power supply is genuinely regulated to the correct voltage ( a switcher should be ) and that the output is clean of switching noise, and therein lies a different story ...

If the power supply that you are trying to use is not new, then I would suggest checking its output with a 'scope, in case its output filter cap has gone high ESR, as is common.

Are you saying though, that the flashgun did not exhibit this problem, and worked completely normally on batteries ? Does it continue to work normally up until the problem with the cap starts ?

If the cap really is leaking electrolyte, then you need to replace it pronto. The liquid that is leaking from it is corrosive, and will damage nearby components and print tracks. Also, if it decides to vent fully, this action can be quite violent, and a considerable amount of electrolyte will be sprayed around the inside of the thing.

Arfa

a buddy of mine (EE) insists that loads powered by SMPS are more susceptible to voltage 'spikes' because the spike can occur when the switch is in the on state and therefore just kinda passes through.

the logic seemed to make sense to me but i don't insist that it is indeed the case.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money"  ;-P

"cybose" bravely wrote to "All" (16 Jan 06 17:07:57) --- on the heady topic of "Leaky Capacitor"

cy> From: "cybose" cy> Xref: core-easynews sci.electronics.repair:355457

cy> II'm trying to see if I can replace 4 AA batteries, with a 6V (2A) cy> regulated SMPS, on a flash unit. The thing is after awhile the main cy> charging capacitor in the flash unit starts heating up and leaking cy> fluid (obviously pretty dangerous). Is there something fundamentally cy> wrong in trying to replace a battery power source, with a regulated cy> power supply?

Depends... for example if the polarity is wrong then the electro will definitely get hot and leak. Other than this I can't think of another reason for the heating and liquid spillage. Someone mentioned the switching supply noise but these are typically quite good in that respect. There might be another factor that is being missed.

A*s*i*m*o*v

... Real techs don't lick nine-volt batteries!

In this case: yes, there may well be something fundamentally wrong. It all depends on the flash unit's design. There are loads of (cheap) flash units that more or less rely on the poor battery performance for their current limitation. Those may even have a hard time if you use fresh alkaline cells. Your's isn't particulary well designed if it allows the capacitor to fume.

Try to imagine, what will happen if the capacitor expodes. Look at the low price for a new flash unit. Look at your kids. Make a decision.

--
Kind regards,
Gerard Bok

:) Thanks

I was thinking along the same lines. It's also possible that there is an initial inrush current requirement, which is not being met by the supply he has....

I tried measuring the charge held in the capacitor (when charged by batteries and before the leaking scenario) and it turns out to be about 750V. But, (this probably doesnt make sense), the rating on the capacitor is 350 SV (1050 MFD, There are no other markings on the Cap.). If the 350 is the surge voltage rating, shouldn't it be much more than the 750V that I measure across the Cap. terminals ?

jakdedert wrote:

If the inverter really tried to put 750 V on the capacitor, it would have spilled its guts all over the room.

Are you sure you were measuring on DC?

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