UPDATE, JUNE 2024: Strobist was archived in 2021. Here is what I am up to now. -DH


How to Keep Your Old Flash from Exploding

Have a flash that's been sitting, unused, for a long time? Or did you buy a used flash with an unknown history? Turn it on the wrong way and you may be in for a bit of a surprise.

Doesn't matter if it is a speedlight, an Alien Bee mono, a Profoto pack-and-head or whatever. Keep reading for a nifty little tidbit of info that may help you avoid seeing that "magic smoke" escape from your babies.


Magic Smoke is very important because once it escapes, your flash won't be working any time soon. Worse, once escaped, the magic smoke is quite impossible to coax back into your flash. Magic smoke often lives inside a component called a capacitor, or cap, which is the thing that makes your flash possible.

For our nontechnical purposes, think of a cap as a bucket that can gather and store electricity over time and then get rid of it very quickly. It's as if you wanted to throw a lot of water in your friend's face but all you had was a trickling faucet. With a bucket, you could gather the water over time, and then throw it into your friend's face at will.

The electricity is like the water, and the cap is like the bucket. Take the juice in over 3-4 seconds, discharge it in 1/1000th of a second.

But capacitors (specifically electrolytic capacitors, the type used in flashes) can deteriorate when they go unused over time. As in one inside a your flash sitting in a closet for a few years. (Without getting too technical, the aluminum oxide layer inside the capacitor can deteriorate.)

In this case, just turning a flash on and waiting a while to "see what happens" is the worst thing you can do. That's because when the oxide layer deteriorates, you can get current leakage in a fully charged state. Which makes more heat. Which makes more current leakage.

It's a vicious cycle. Lather, rinse and repeat until, in some cases, it will actually blow. Not good.

The Right Way

Assuming you don't have a full electronics bench and a variable transformer, you can actually (re)form the thin layer of aluminum oxide that may have deteriorated from your capacitors.

The best method to do so depends on how your particular flash is designed. Here are a best practices for a couple common designs to give you an idea. (But you should definitely check with the manufacturer to learn the best method for your particular model.

Example: Paul Buff Flashes

1. Dial the power control slider all the way down before turning the flash on. If the flash is a powerful model such as a WLX1600 or WLX3200 (with capacitor switching) make sure the quarter-power switch is not engaged. (You want all of the caps to be involved in the process, and they are not so at the quarter-power setting.)

2. Turn the flash on.

3. Pop the flash for 5-10 shots at the lowest-power setting. (If you can trigger the flash remotely, that probably would not be a bad idea.) This process will partially cycle the capacitor while giving it time to reform the thin, insulating oxide layer that it needs to work properly.

4. Raise the power level one stop and repeat step #4, slowly working your way up to full power. This will help to avoid the possible "thermal runaway" vicious cycle described above and will in many cases safely rejuvenate (or "re-form") a capacitor that may have deteriorated over time.

Example: Speedlights

Speedlights are designed so that the capacitors remain fully charged (to over 300v) when the unit is on. So working your way up from low power can actually be a problem, as you are leaving the cap in a near fully charged state most of the time. Which can cause a thermal runaway.

The process is just as easy, just a little different:

1. Turn on the speedlight and set it to full power.

2. As soon as the capacitor charges up (ready light glows) fire the flash.

3. Repeat the process.

4. Alas, speedlights do not dissipate heat very well when popped repeatedly at full power. And the last thing you want here is heat build-up. You may wish to turn the flash off and let it rest and cool every twenty pops or so.

5. This technique will build up the aluminum oxide layer on the cap (assuming it was not too far gone) and breathe new life into it.

Whichever method is suited for your dormant (or history mystery) flashes, the amount of deterioration in the caps is a function of how long they were dormant, (longer is bad) how hot the storage area was (heat is bad) and how humid (ditto moisture). So flashes which have been stored for long periods of time in hot, humid environments will take more time to re-form the oxide layer in the caps.

A technician with testing equipment can track the rejuvenation of a capacitor as she/he goes. And a badly deteriorated cap can take a full day to reform. (As you build up the oxide layer, you can extend the time between pops.) If you are not sure, just stick with it for awhile. But don't leave the cap in a fully charged state for very long at first.

And sadly, some caps are so far gone they are beyond reforming. I.e., they may explode no matter what. But understanding the process (and best practices) will give you the very best odds of saving/restoring an old flash.

And it bears repeating: Check with your unit's manufacturer. And if your flash is a mystery rebrand from who-knows-where, best of luck to you! (The availability of tech support is a very good reason to buy from reputable companies with a track history.)

News to Me

The high-mileage White Lightning Ultras seen at top are my backups to my backups. As such, they have not been used in many years. And when called into use (or passed on to someone else) they may well have been ripe for just this type of nasty surprise. As could any flash, including a speedlight.

So I'll be watching a movie and popping flashes as I give the caps inside a little TLC. Even if they are not deteriorated (but the probably are) it won't hurt. And I'll feel much better about my using them, or, more important, someone else doing so.

Appropriately, this little insight into capacitors came as a "by the way" moment during a recent conversation with Paul Buff. Paul designed and built these Ultras nearly 30 years ago in the mid-1980's, which is exactly when I was first getting serious about my lighting. (Suffice to say I used the living crap out of these lights.)

As such, I have long felt a connection to Paul and his gear and am always grateful to get the chance to talk with him. And I almost always learn something I did not expect to learn.

This time it happened to be interesting (and important) enough to where I thought I would pass it along.


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