boiling capacitator?

[AgX]

I just "waked-up" an old flash-unit of the hammerhead style, a Sunpak Autozoom 3600 (a model from 1978).

First surprise was the extreme loud noise of the oscillator. When charged everything went calm except for some trickle charging that went over too in the forming period..
In the firing test which I started in lowest manual setting, the handle (with the main capacitator) got warm after firing at full power a few times. At this period the extreme annoying noise of the oscillator returned.
I considered the source for the warmth to be the transfomer. But in the times the oscillator went quiet again, I heard a weak noise from within the handle that reminded me of cooking fluid...
No hiss sound, no smell.

Though what puzzles me is that except for the first charging of the capacitator the following cycles remained within the stated range. With strongly leaking capacitator I would expect longer recycle times than normal. I did not meter the output. What I should have done.
In hindsight my forming process was not best structured and likely too short.

I would have inspected the capacitator by now, but so far I refrained from tearing off the bottom seal that likely covers the respective screws.

The flash unit was intended mainly as show item anyway, I prefer not to use one with a capacitator likely to blow...

Thus my interest in the cause of that warming up and that strange boiling sound is rather academic.
Maybe though it is quite normal for this model.

 

[Larry the sailor]

Capacitors can get old and leak. When it happens it can cause all sorts of nasty problems with electronic circuitry. It's possible the unit could be repaired but a decision based on cost versus value would have to be made. I wouldn't use it "as is" and would remove any batteries.

 

[AgX]

So far I never came across a leaking flash capacitator. (Just now I mean wet-leaking to the outside.) All kind of nasty faults but not that one yet.
I assume though that a dried out capacitator in contrast would show no signs as a leaking one.

And so far it seems the capacitator was still producing the right output at normal cycling time.

 

[paul ron]

Caps have vents for a better controlled failure n should keep it from exploding. What you are hearing is a cap venting... Boiling out.

That flash would look great on the mantle perhaps hooked to a nice old camera.

 

[AgX]

It is a mint one, good to show. I have many other ones, except for that this one offers power reduction down to 1/64 without accessory.

To open it I would have to break open the sealed bottom. In the best case I would find the transformer getting really warm. In the bad case I would find the capacitator boiling.
Replacement only would be economical if I really needed that model.


Any one more thinks the capacitor got hot?
If so, could another, longer forming session cure it again?
I'm very sceptical.

 

[ic-racer]

My test of leaking capacitor is to turn the fully charged unit off then back on again after a while. It should not need to charge at all unless quite some time has elapsed or you fire it. My most leaky units continually cycle , that is every 20 seconds or so they need a little zap from the charge circuit and you can hear that (even when you have not fired the unit).

 

[AgX]

There are screws at the top but is does not flip open. Seems tightly fixed at the bottom and as their type 662 also has a screw under a cover I think it is the same here. But that bottom cover sits there without the tiniest slit, as if moulded in, hardly a way of removing it without breaking it. Also it is hard to imagine the handle halves just to flip open without breaking that plate either.

 

[AgX]

I never heard a oscillator that loud, really annoying after three or so full discharges. Which made me think the charge current is too strong. But then the oscillator shuts off completely again which it likely would not do with a severe leakage of the capacitator.

 

[Jim Jones]

A leaky high voltage diode might overheat the transformer and distress the capacitor.

 

[AgX]

Thank you. I shall think about that.

So far I was lucky with my countless flash units. Practically all worked fine at first charging.

Back in the 70s the built-in NiCd pack of a compact 10 years old Metz unit wore out and I had to get appropriote cells, solder a new pack and install it in the the circuit again.
And recently a seemingly unused unit from the rummage box, of a model of which I got several samples, who form the majority of my flash power, when switching on started smoldering immidiately.

 

[Les Sarile]

I never heard a oscillator that loud, really annoying after three or so full discharges.

It may be your resonant frequency that makes it more annoying then others!

Most of the failures I have seen are batteries leaking inside and corroding the contacts.

I couldn't find the schematic for the Sunpak Autozoom 3600 but this site may be of interest Dead Link Removed
I doubted there are any boiling capable capacitors used in these compact modern flash units as I generally only see them in the very high voltage/high current applications.

 

[AgX]

Most of the failures I have seen are batteries leaking inside and corroding the contacts.

Yes, the major fault of all electric photographic equipment. One would be lucky then if it was a something still equipped with zink-carbon cells.

And yes I know that site you linked to, but have not yet looked through all pages.