(Almost) shot dead by my flash

[David Lyga]

I recently bought a Vivitar SMS 30 flash for the outrageous sum of one whole dollar. It came complete with highly corroded batteries (4 AA) and I did yeoman's work opening the battery compartment only to find an utter mess.

I spent the greater of 30 minutes carefully cleaning the compartment and filing the contacts (so I could make contact!) Then came the moment of 'bargain affirmation'. I inserted four fresh batteries and heard the flash rev up!! Then I pressed the trial button and it went off! I affirmed this about 10 times and the capacitator seemed full of vigor.

Then...a loud 'shot' went off followed suddenly by a whiff of smell that seemed smoke (but not visible). The shot jolted me and I knew that the graveyard (for the flash, not me) was immanent.

What caused this? This is a warning for all to heed...NEVER take apart a flash, EVER. I am lucky that my curiosity did not get the better of me. A whole dollar shot. Imagine. - David Lyga.

 

[BrianShaw]

If you take it apart one more time you might find the failed component.

 

[benjiboy]

This is no joke, even small electronic flashes are capable of delivering 10,000 Volts and a fatal shock.

 

[David Lyga]

Yes, Benjiboy, I think that this important point is not made clearly enough in the industry (or the government). VERY important to state this redundantly.

Who, after all Brian, (besides myself) do we want shot? - David Lyga

 

[David A. Goldfarb]

Any older electrical device can potentially blow a capacitor, and strobe units tend to have big ones (studio strobe units have REALLY big ones). I had one blow in a densitometer of all things--loud pop, smoke, oil leaking out, the works.

 

[BrianShaw]

Don't you just hate that smell too? I've smelled more burning electronics than I care to recall. HATE THAT SMELL!

 

[jeffreyg]

Many years ago my wife had a point and shoot that stopped working. I decided to take it apart just to see how it was made. I accidentally touched the capacitor and as it burned a hole in my finger, I tossed the camera in the air. I retrieved it after two or three bounces and put it back together. It worked afterward. The secret to repairs is to know how high to throw the equipment for a particular malady.

http://www.jeffreyglasser.com/

 

[BrianShaw]

LOL!

 

[David Lyga]

Again, I hope that there are a lot of 'newbies' reading this because the danger is real and innocent in appearance. Once, maybe ten years ago I decided to take apart a small flash but (wisely!?!?) I discharged the flash before I did this. I was still scared but stupidly bold. I did take it apart and saw two contacts that I thought would be completely tame. Wisely, really wisely, I crossed them with a screwdriver, but one with a plastic handle (because I was still scared). The spark and noise that flew out of that tame piece of electronic synergism educated me for life. 'Nuff said. I ain't dead yet. - David Lyga

 

[BrianShaw]

In all seriousness, which I may have lacked in previous posts, this is a good warning!

 

[David Lyga]

And redundantly Brian, LOL: Let's Offer Leniency (with electronics) - David Lyga

 

[Worker 11811]

I'm pretty sure it was the flash capacitor that blew up.

There's usually a voltage multiplier circuit that charges the capacitor. If one of those diodes failed, it could have reverse biased the capacitor. Electrolytic capacitors don't like reverse voltage. That causes the electrolyte to boil and... POP!

Smells awful and the smoke is not good for you, either.

I had a rectifier in a movie projector that blew the filter caps, once. They were as big as beer cans. When they went, they spewed foul smelling oil all over the inside of the housing. YUCK!

Given that I don't know the construction of the circuit that the flash unit uses, I could not advise on how to repair it or whether it is repairable at all. Generally speaking, the capacitor and the diodes that feed it could be replaced and it might work all right. However, that begs the question whether you have the wherewithal to do the job, not to mention the inclination.

It's probably best to junk the thing or scrap it for parts.

As others have said, flash capacitors can contain thousands of volts. Be wary of them! Be absolutely sure they are discharged (by shorting the terminals together) before you do anything in the vicinity of them.

When I was in Tech school, we used to cannibalize old flash units to make flash welders for soldering paperclips together.

Touch the wrong thing and you were in for a nasty jolt! If it goes through your chest it could quite easily stop your heart!

 

[jerry lebens]

Trainees are always surprised to learn that flash equipment is lethal and should be treated with respect.

I had a 5kJ studio unit explode once, quite spectacular!...

 

[Newt_on_Swings]

Oh I know the feeling, did this a number of times tinkering with single use cameras haha

 

[Roger Cole]

Nah. I know my way around electronics well enough. I've worked on 2kw amateur amplifiers when I was in high school, and was a TV transmitter engineer on a 30kw VHF station for 8 years. I'll gladly take apart a flash. I might not be able to save it, but I am not afraid of it. Yes, it could be deadly (though pretty unlikely - more likely "unpleasant") but so could many other things.

 

[pentaxuser]

This is not to encourage electrical foolhardiness but I always thought that it was voltage combined with a high/highish amperage that was the killer.

The HT leads to car spark plugs will give you a significant jolt but if you are healthy it won't do you harm as the amperage is very small. As I understand things the voltage from "old sparky" - former execution weapon of choice in the U.S. operates at a much lower voltage than say a car HT lead but the amperage combined with the voltage "does the job"


Is a flash gun not more like the car HT lead rather than being like "old sparky"

pentaxuser

 

[Roger Cole]

For most people pentaxuser is correct. The spark from a doorknob after walking across dry carpet is thousands of volts at very very low current. But there is probably enough in a charged flash capacitor to harm someone with a pacemaker or existing cardiac arrhythmia. It just takes a bit of care not to get zapped at all though (though the bang from an exploding cap will get your attention.)

 

[mwdake]

Is a flash gun not more like the car HT lead rather than being like "old sparky"

I don't know the technical answer but in my experience they are not the same.
I have had jolts from both.
As kids we used to test HT by holding the wire and cranking the engine.
And I got zapped by a point and shoot taking it apart.
The later was much more memorable.

 

[polyglot]

Less hyperbole please, it's not 10,000 volts; that would cause the tubes to spontaneously conduct and you couldn't trigger them at a desired time. The main caps are at about 300-350V.

While the trigger coil can produce about 5kV it's so small (tiny current) that there's a good chance you couldn't even feel it.

What matters though is the total energy and even a small disposable P&S with 7J can hurt you badly. A big hotshoe flash can be 100-150J, and that can kill you if it goes across your heart. Across your fingers though it will just cause burns and a big reflex, often resulting in the offending item taking flight.

The dangerous thing that many don't realize is that older capacitors have dielectric memory: just because you discharged it doesn't mean it will stay that way! The voltage can climb back up (without application of power) to the point where it can bite you again.

The upside is that collecting the plastic disposables from a lab has been an excellent source of HV capacitors for me! I have about 2kJ stashed somewhere waiting to be turned into a railgun.

 

[tkamiya]

Nah. I know my way around electronics well enough.

I believe one big difference between those of us who call ourselves a trained professional and amateur/non-pro/inexperienced is that we know enough to realize, notice, and identify when and where we need to stop, take our hands off, take a measurement or two or three, double-check, and proceed, and not even noticing it and killing or hurting ourselves.

I am also an amateur radio operator, some professional electronics experience in small and medium power electronics, and a licensed electrician.

Through training, experience, and dumb mistakes (that I almost killed myself) I made through the years, I learned to respect any electrical circuit with respect (especially around large capacitors!!).

 

[Grainy]

I once saw an old camera get toasted because of lithium AAA batteries. A loud bang was followed by smoke and the smell of toasted electronics. And then the camera was dead.

 

[johnielvis]

FIREBALL

YEE HAAAAAA

SAME thing happened to me...like 15 years ago---I bought these strobes from the 50's or 60's...they were like metal boxes---Hershey Hi-Pro's made in chicago, IL right by some place on Lake Street.....long defunct...ANYWAYS--can't forget that name from the equipment tags--it's literally BURNED into my memory

one acted erratic (got 2)...so I decided to see if I could fix it.....being smart, I charged it up full...then I popped it and immediately unplugged it---so that the caps would be completely dead --- SEEEE I KNOW what I"m doing...nice and safe...

anyways...so I figured It may be best to wait a day or two as well, just for good measure before I touched them...make any residual charge bleed down. See--very safe....

After a couple of days, I figured, time to take 'em apart---FIRST, to be TRIPLE safe, I figued I'd short out the terminals to the flash tube...just to make double double sure....I even got a nice insulated THICK screwdriver to do the deed with....expected...hardly nuthing....shorted itZZZZZZZZAAAAAAPPPPPPP

B O O O O M

FLASH!!!!!

all in an instant, a fireball shot out at my face.....lucky I kind of had my head WAY back just in case...WOW (and was wearing glasses)....

I threw them both right in the garbage

these had like redbull sized cans for capacators.

I talked to my friend the soundman about it--he said that it was to be expected when you leave capacitors alone for a few days, the electrolyte dielectric migragtes and it builds up a charge ON ITS OWN....he said they are VERY dangerous because of this...

live and learn.

I bought my first set of calumet travelite 750s after that and still have them to this day.

lucky

 

[Roger Cole]

You should have discharged them with a resistor across the terminals so they discharged at a safe rate instead of all at once with a boom. As you say, live and learn.

I would also point out that you lived, and were apparently unharmed. I bet the "fireball" was more the impression from the arc light than a real ball.

 

[tkamiya]

I'm surprised it recharged to THAT kind of level. I've experienced this too but the "second pop" has always been rather small and puny. My routine used to be, discharge it first. Then discharge it again and keep the caps shorted with a lead while I work on the circuit.

The first "pop" is always a nice big one. Second pop is usually a just a small spark. I still don't want to be shocked by it, so I kept a short lead with clips at the end connected across large caps.

I have a real bad experience with trusting those bleeder registers across large caps. NEVER trust these.... I have a burn on my finger to prove it.

 

[M.A.Longmore]

.
My father was an electrical engineer so he did warn me about tampering with
flash units. But, He didn't warn me about MagicCubes that were used with the
Instamatics, and pocket cameras. So I attempted to take one apart, and was
extremely surprised when I got my fingers burned, and severely blistered.
I Never had the need to experiment with those Cubes ever again. I can image
the YouTube videos that would be produced if those things were still being made ...

Ron
.