Strobe Failure – A note of caution

Strobe Failure – A note of caution

Wetpixel carries sad stories of underwater strobe malfunction or burn out while shooting (ref 1) but at times important details are missing, such as if the strobe was being fired in rapid sequence, in the water or in the air. This is important to know, as strobes overheat when fired rapidly in a row, particularly when out of the water.

The makers of underwater strobes clearly warn about this danger. For example, the Sea & Sea YS-D2 manual states:

"CAUTION. If the full flash has been activated ten times in a row, allow the product [the strobe] to rest for 10 minutes before attempting to use it again."(ref 2) and in the Inon D2000 User Manual we read:

"Do not fire the strobe on land except for functional check. Do not fire the strobe at short intervals during functional checks to avoid malfunction of internal circuit,"

and

"Never repeatedly fire the strobe continuously, for example, to test, discharge or refresh the batteries." (ref 3)

The reason not to fire the strobe rapidly in a row, even in the water, is that the high voltages used to charge and fire the flash tubes generate a lot of heat, which takes time to dissipate as the flash tubes are mounted at a distance from the outside cool water. The plastic bodies of popular strobes further help retain the heat. When fired in a row in the air, overheating and burn out are an even higher risk. One needs to keep in mind that underwater strobes are designed to work in cool water, 0°1 to 30° C, not in air.

Another warning from both Inon and Sea&Sea is to not aim the strobe downwards while firing, as it damages the circuits. This may be because an internal switch or similar device needs to be horizontal to work properly, but no reason is given.

Two suggestions for safer strobe shooting:

Shoot more deliberately and slowly, space the shots to give the strobes a chance to cool off.

Do not shoot in a row when out of the water.

References:

1. Our strobe problem.

http://wetpixel.com/forums/index.php?showtopic=63956&page=2

2. Inon D2000 User Manual,Type 2, Basic Operation, p 6.

3. Sea&Sea YS-D2 Instruction Manual, O3117, 2015, p E-23.

A Wetpixel post by Wolf Eel is strikingly relevant to strobe failure overheating:

" I've had the exact same thing as Custom happen to my D1s. The flash tube design shortcoming/flaw was not addressed in the D2, which is why I did not upgrade to them. SEA&SEA's explanation to me was [paraphrasing] "we are very sorry but this can happen because the flash tubes are those taken from conventional land based flash units and simply housed in an underwater housing (sealed, traps heat) - we do not have the resources to design from the ground up a flash tube assembly just for this strobe". They told me not to fire them 10 times at high setting 'in a row' and that if I did I had to wait 10 minutes for them to cool down. It does indeed say this in the manual of both the D1 and the D2. However, when I asked them "ok, what about 12 shots at 80% strength - what's the cool down time there?" they said they couldn't answer and to just use my best judgment in not rapid firing them like I must have to burn them out.

I never had this problem with the YS-250PROs and I'm really hoping they come out with a redesigned successor to those or that they address this shortcoming in the next iteration of the D2. An underwater strobe should simply not overheat from usage or rapid fire (running out of juice is understandable). At least that's what I think as someone who has come across a baby whale shark and a completely white manta on the same dive "

http://wetpixel.com/forums/index.php?showtopic=57102

Part of my maintenance routine for strobes is to exercise the capacitors regularly. Basically, this involves running the strobes through discharge and charge cycles when I don't get to dive regularly. I do this routine with the strobes submerged in cold water.

It would be interesting to see the Sea & Sea data regarding how much heat is actually retained by their strobe housings in an underwater environment. Plastic and metal are typically not very good insulators. Those materials usually conduct heat and cold pretty quickly and air doesn't work very well as an insulator either... just saying...

-AZTinman

Still air is actually quite a good insulator, and most insulating materials work by trapping small pockets of still air- just look at double glazing - the insulation comes from trapping air between the panes. Plastic has significantly lower conductivity than metal which is why pots and pans often have plastic handles, you can pick them up without protection on the stove. INON now has a heat sink onto which all of the heat producing components are attached and that extends to the outside to conduct heat to the water. Retra makes their housing from aluminium to assist with shedding heat, so these manufacturers are attempting do something about the heat problem. INON Z-330 heat sink is described here: https://www.backscatter.com/Inon-Z330-Underwater-Strobe

I suspect that the ring shaped tubes are significantly more expensive so they use off the shelf straight tubes to build to a price. The ring flash also has more surface area so probably runs cooler than the straight tubes.

This is entirely anecdotal, but for review purposes, I have fired Inon Z330, Seacam 60D, Retra (original), Symbiosis, and YS-D1's as fast as they will recycle for over 3-400 flashes. In each instance, the batteries were changes and then were cycled for a similar number of times for at least 3-4 complete cycles. They were in a bucket of water while doing so.

I can report that none of them how any signs of damage for having done so.

As it happens, I would imagine that at least some of this testing took place with the strobes pointing down too.

I would imagine that the strobe manufacturers give fairly conservative guidance on how to with their product.

Adam

I have had issues with the Z240s burning out both in air (caving, used cautiously) and in tropical waters when shooting on full power. I had tubes replaced locally about half a dozen times. A thermal cut-off switch is not that hard - it's frustrating that the strobe manufacturers don't think this is important. More frustrating because inon won't replace tubes, they just replace the entire internals and charge accordingly.

I have not had any burn out issues in cold caves (6 degrees air temp) or in temperate waters (4 to 22 degrees).

I shoot on full power most of the time.