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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Blogger budrowilson said...

Very interesting and useful information.

The team over at Paul C Buff (and, as it seems, Paul himself) are amazingly helpful. Their customer service is next to none; it stands to reason that corporate culture is a "trickle down" from the very top.

June 14, 2013 9:15 AM  
Blogger Gary said...

How long is a "long time"?

June 14, 2013 9:55 AM  
Blogger R. J. Kern said...

I feel like my grandfather just taught me one of those annoying lessons that will save my keister more than I know later (turning off cruise control on ice, checking my credit once a year, how to repair a lawnmower the right way, etc). David, thank you for sharing your knowledge, and enthusiasm.

Just received the bill from PhaseOne for that leaf shutter repair.... about half the price of a new one. Doh! There'll be a few lessons on what went wrong posted soon.

Perhaps I'll follow your lead, "How to Keep Your Leaf Shutter from Exploding."

June 14, 2013 10:48 AM  
Blogger Alex Minkin Photography said...

I'll never forget when a B2 pack blew up over 3 pops during routine testing.

pop (cracking noise)

POP (even more cracking)

Hey Tony, do YOU want to check this light out?


June 14, 2013 11:23 AM  
Blogger MikeScottPhoto said...

Interesting read.. leads me to something I've wondered for a while. Do flash tubes wear out or deteriorate over time? Does the color shift? Or if it works, it works - and when it doesn't it doesn't? Wondering when it's time to replace a flash tube in an 12 year old Calumet Travelite 750 for instance..

June 14, 2013 11:54 AM  
Blogger Erik Hawkinson said...

I didn't spend a long time looking into this, but I was curious about this. According to this article, capacitor reforming should be done at least every 2 years:

June 14, 2013 12:21 PM  
Blogger Andrew Wisler said...

While I wouldn't recommend doing this yourself (dealing with lethal voltages here), it should be a relatively simple job for a qualified technician to replace the caps. This is commonly done in older electronic equipment, e.g., old tube amps and the like, as the electrolytics are well-known to degrade over time. It should be a 20 minute job and would probably be worth the price to prevent destroying an old studio light.

June 14, 2013 12:55 PM  
Blogger Wink of an eye Digital said...

Good advice to people that don't know what caps are.

Some older strobes from e-bay have this problem when sold. Usually some people don't even know that they are sending a bomb. Buyer if it Pops like a gun (big gun) send it back. If you have heard this and can't send them back Do what DH suggest If you still hear it once in a while it is leaking power. You can however purchase some caps from a OEM provided that You know the OEM

June 14, 2013 1:09 PM  
Blogger Randy said...

I have a Comet 1250 pack that I've used for 20 years now. One of my assistants didn't click a cord in completely during an outdoor shoot and while I was firing away, I heard a sound like bacon frying in a pan. The cord was shorting at the connection to the pack!

That was an expensive repair. They replaced a few capacitors. In the past 10 years, I've been using my Speedlites primarily. They are wonderful as is attested to in this very blog. I pulled out my Comet pack for a long day of shooting dancers and it started overheating. To the point that I had to shut it down and put a fan on it, just so I could keep working.

I sent it in and the repair tech said a couple of the capacitors had actually melted! They replaced them and warned me that due to the new vs. old, the voltage levels would be different and I could expect to see a ripple effect of new ones failing.

It still overheats, but I use it from time to time. A new pack is $2K+ and that just isn't going to happen any time soon around here! Sage advice and something no one ever talks about. Probably because the industry is full of photographers with less than 5 years experience total. But THAT is another story all together!

June 14, 2013 1:17 PM  
Blogger Gordon Huston said...

David: How about Einsteins? Isn't their design more akin to a speedlight than a traditional strobe unit? How should they be cycled?

June 14, 2013 1:24 PM  
Blogger emerym42 said...

Thanks! I've got a bunch of studio heads that don't get used as much as the others as they don't have the same mounts, time for some maintenance!

Many modern caps have indentations in their cans or rubber bungs so when they break down and pressure builds they rupture and vent safely.

Older caps can go like a fire cracker!

June 14, 2013 2:07 PM  
Blogger James said...

That is extremely useful information. I've got a bunch of flashes that are about to see work after sitting for a few years.
I've got an Ultra 1200 I've been an extra bit afraid to test it's been sitting so long.
Even better knowing it came from the man himself, Paul Buff.

June 14, 2013 3:24 PM  
Blogger Stan Strembicki said...

Thanks for the posting. I was told once by a Speedtron repair guy that you should always power up a studio strobe power pack and leave on, but do not discharge for 30+ mins before use if you have not used the packs for 4 or 5 months. Not sure this guy really knew what he was advising.

June 14, 2013 3:53 PM  
Blogger BillyB said...

What would the procedure for Profoto be? The manual says nothing about this, not surprised.

June 14, 2013 6:54 PM  
Blogger Southern Skies Coffee Roasters said...

How timely, seeing that I got my first Einstein today!

June 15, 2013 1:16 AM  
Blogger david said...

I've been acquiring and repairing Norman 200B packs since late last summer.

I was fortunately that six out of 8 came up with no issue. At first, the time between recycles to keep the voltage up was short. After sitting at voltage for a while, the time got longer and longer.

One of the packs badly needed reforming. I was able to coax it up to full voltage. All seemed well until it popped very loundly several times. I did not see any magic smoke come out but I full expect to have to replace the caps in it.

I've just gotten another pack with a capacitor that needs reforming. Instead of bringing it up to full voltage, I'm using a low voltage power supply and they're slowly coming up. Hopefully, they'll recover and this will be a serviceable pack once again.

June 15, 2013 11:09 PM  
Blogger James Brown said...

My Speedotron 2403B pack is 26 years old. Once a month whether the pack has had recent use or not, it gets plugged in and powered up for 8 hours, without discharging. This process for Speedo packs came straight from a repair tech when I bought it new. It is still working and performs flawlessly.

June 16, 2013 9:41 PM  
Blogger Unknown said...

Just spoke with Dynalite, here's their guidlines:

- set variator at minimum
- plug in pack and let it idle for 24 hours (do not pop strobes while idling)
- after 24 hours, increase variator one click every 2 hours
- once variators are at maximum, let packs idle for another 24 hours

Their tech said you do not need to have heads plugged in and it does not matter if the channels are split or combined.

This was their advice for 1000xr and 500xl packs. I did not ask if these guidelines apply to all Dynalites.

June 17, 2013 4:45 PM  
Blogger Eye said...

Hi David,

I am taking a trip across America on motorcycle that was inspired by one of your blog entries.

If your interested in reading about my trip, you can visit my blog at:

Thanks for all the great advise over the past (wow!!) seven years.


June 17, 2013 9:18 PM  
Blogger David Hobby said...

Hey Duane-

Very cool, and safe travels. The post had contact info for Bjorn, so I am sure he could help you with advice if needed before you leave.

Bon voyage,

June 17, 2013 10:55 PM  
Blogger bruggles said...

Question - how do you know if the capacitors have deteriorated (other than Magic Smoke when they're all the way gone), and when refreshing them, how do you know when you've done enough? Thanks.

June 18, 2013 9:06 AM  
Blogger david said...

Reforming old caps should only be attempted if one is fully aware of the lethal voltage involved and what can be safely touched and when. Discharging charged caps before touching anything is an absolute must.

That said, here are some links to how to treat old aluminum electrolytic capacitors:

I have been pretty fortunate with the number of Norman 200B packs I have brought back to working order. This last bad pack I noticed right away the voltage would not go above half the normal 500V so I tried using a low voltage power supply. Even with the low voltage supply, the caps never came back and will need to be replaced. On the other pack, one of the caps popped and some electrolyte leaked out.

June 18, 2013 4:09 PM  
Blogger Bernhard A S said...


I do not really agree fully with your post David.

You explained that the dieelectrical paste in the capacitators "looses" its insulating nature when the capacitor is without charge for a longer time.

Charging it, causes the paste to slowly "re-form" itself simply by virtue of the charge being present. Any slightly "out of shape" capacitor has an automatic self healing effect when charged. There is no need to pop any flash for it.

Most manuals have a section where they recommend to simply switch on the flash for 10 minutes every three months.

If the insulation is badly damaged there will be a short circuit in the capacitor and it will blow.

The slow loading and popping flashes procedure you describe is actually only necessary, when one tries to coax a badly damaged capacitator back to life. Building a small charge and getting rid of of it must be done, because a full charge would already blow it.

In my experience/opinion it is better to give up on a cpacitator once it has reached the stage where these kind of tactic in necessary.

At that stage a growing part of the damage might be permanent and by coaxing it back to life you simply have a ticking time bomb on your hand.

For an expensive flash, I would rather get the capacitor replaced by service. A cheap flash should be relegated to the museum or end in the recycling bin.

Every three months switch on all flashes you own. Keep them on for 15 - 20 min min and pop them once.

It is not loading or emptying the capacitor but a steady charge that enables the self healing.


June 24, 2013 9:12 AM  
Blogger David Hobby said...


I don't know if you read all the way through the post, but the advice I gave was straight from a man who has sold literally hundreds of thousands of studio flashes. That he designed himself. So I'll defer to him on that.

June 24, 2013 9:19 AM  
Blogger Jyrki K said...

I Just fried my Multiblitz Varilux 1000S yesterday doing this flash cap recovery. I slowly dialed up more power in 1/10 increments. When I got to level 4 (half power @ about 500Ws) I heard a puffing sound and heavy cloud of smoke came out. I had to keep all windows open for an hour or so to get the bad smell out of the house.

Ancient Profoto 81 just keeps ticking.

August 21, 2013 10:44 PM  
Blogger Richard Swearinger said...

Here is the advice from a 2009 post on the Nikon USA site:

"Take the Speedlight out once a month, insert the batteries, and fire the unit several times to reform the capacitor."

September 08, 2013 1:04 PM  
Blogger illumiquest said...

I have to absolutely disagree with this. I've worked for a camera shop who deals with a ton of used gear including all manner of studio strobes. They've always plugged their packs in and left them plugged in with no heads attached for 12 hours or more to reform the caps. This has worked very well for them.

But, having found this post, and it's rather convincing sounding nature, I decided to give it a go on a pack I just bought that I know hadn't been used for several years. It was a norman P2000D, I turned the power all the way down, and popped the strobe about 10 times. Waited a minute at which point the pack started smoking, a lot. Then started making nasty noises at which point I unplugged it.

Dead pack.

I've purchases several of these packs over the years and always listed to my old bosses method of plug it in, and leave it alone. And never had a studio fire.

I have no idea how electronics work, just what works and what doesn't. The pop pop pop method does not work.

April 03, 2014 3:44 PM  
Blogger Mark Beaumont Photography said...

Wish I'd seen this post last week......currently got a Profoto B# pack in the workshop waiting for assessment, though it sounds like I may have not only fried the capacitors, but the circuit boards too!

Unit went from not being used for two years to full power test.....lots of frying noises, lots of smoke ;-(

September 19, 2014 8:47 AM  

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