discharging capacitor on 580EX flash

I don't know what the full-charge voltage is in a 580EX, but like Jeremy I suspect it's 300-400 volts. In any case, the way to discharge it is to turn it on, let it charge fully, turn it off and then hit the manual flash button on full power. This will discharge the capacitor to the sustained-arc threshold of the flash tube. That's probably around 100 volts. (It takes about 50% more voltage to initiate an arc in a gas tube than to sustain it.)

Then you discharge it with a screwdriver after it's open.

-js

number six wrote in post #9512654
Then you discharge it with a screwdriver after it's open.

-js

You can actually damage some caps by using a short to discharge them. Much better to use a resistor. I was making fun of whoever wanted to use a 1 meg resistor. Probably something on the order of 100K is better

However, I doubt very much the OP has the skills needed to fix this thing. I would if I could ID the components---and that's often the problem---many consumer products are not made to be repaired, and therefor have no service documentation, parts lists, or anything else, and often contain proprietary or unmarked components

Additionally with the control circuitry involved with any modern dedicated flash, are YOU willing to risk damage to an expensive camera body because you made a wiring mistake on a flash?

I have taken part a 430ex and a 580ex in my life, a friends not mine (I know how that sounds). The capacitor is in the flash head not in the lower half. One time it was a broken solder connection in the hot shoe area, the other was the "ZOOM" function had stopped working and I had to get the flash head back on its rail. Both of these problems were because of it being dropped. So you really need to have an idea of what you are going to be looking for.

A simple, but not guaranteed, way to discharge is to turn the flash on, hit the red light quickly 20 times and quickly shutting it off while you are hitting the button. Although this may not be "safe", it is more safe than a fully charged capacitor.

Before I get flamed, you should be wearing these gloves.....
http://electricglove.c​om/

Pmolan wrote in post #9513563
A simple, but not guaranteed, way to discharge is to turn the flash on, hit the red light quickly 20 times and quickly shutting it off while you are hitting the button. Although this may not be "safe", it is more safe than a fully charged capacitor.

Agreed. See my post above...

Before I get flamed, you should be wearing these gloves.....
http://electricglove.c​om/

And, may I also say, "Haw, haw, haw!"

Totally ridiculous.

Let me explain: I worked for 35 years for The Phone Company - many different names, but you know who.

Every couple of years we had to take a so-called "safety" class. We were always told we had to use the heavy rubber gloves with the cotton gloves underneath before we could touch our own wires on a telephone pole that had power above.

Never mind that nobody could ever do the ordinary things we all had to do with small wires.

We were told that if we got electrocuted and were not wearing those huge gloves, it was our fault. Not the fault of The Company.

Idiotic and legally useless. But stupid managers insisted on this "safety" threat.

Why did I retire? I got totally fed up with the crap and my 401K was healthy. So the last time it was "Up yours! I'm outta here!"

That was nine years ago. No regrets...

-js

Hey,

When I talked about the 1Meg resistor, i should have suggested to leave it during all night.
To me the latex gloves would be an efficient protection, only to avoid my sweety fingers to touch any of the contactors.

I am also asked to work with the electrical gloves, but there is no way you can work with them, we use them only when we our doing the no-tension test, then we earth the equipment, and do our job.
The rubber is so thick that you cannot even use a cell phone, or a multimeter.

To come back at our talk, if the flash has not received power supply during few month, it would probably be discharged, and the best thing to do is to check the voltage with a multimeter, then, you are sure about the hazardous operation you are doing.

KR