Confounding problem with intermittent strobe firing

I've been having a confusing problem for the last few weeks where one or both of my strobes stop firing during a dive. The strobes work before the dive. They work after the dive. The stop working at some point during the dive.

Here is my macro setup used for these dives:

• Nauticam D850 housing
• Two optical cables, 2mm fiber with proper connectors
• Inon 330 strobe with brand new eneloop pro batteries
• Backscatter MF-1 mini strobe with brand new recommend brand 18650 battery
• I recently put in fresh coin cells for the Nauticam strobe trigger

Last night I did two dives near Seattle. Air and Water temps were both about 50f.

During the first dive I test fired everything in the shallows before beginning the dive. After about maybe a dozen shots, not in rapid succession, I noticed the Backscatter strobe was not working. This strobe is definitely more "sensitive" than the Inon and demands the perfect battery, but I had that in place. The Inon continued to work for the entire dive, but I really did not take more than maybe 30 shots the dive. 

Before the second dive, about three hours later, I swapped in a spare battery for the Backscatter. I test fired both strobe on land, and again as I entered the water. After just a couple of shots the Backscatter died again. About 15 minutes and 20 shots later the Inon strobe died. I consider the Inon 330's to be real troopers. They always work. Except for today. I connected and reconnected the optical cable on both strobes. I visually confirmed that the red trigger pulses were bright and visible at the end of each cable. Reconnected, powered off and off both strobes. Nothing. Both refused to fire. Both strobe's Spotting lights worked fine.

I soaked the full rig in the sink overnight and put it on my work bench. Nothing has been opened or changed yet.  I powered everything on again and fired each strobe about 25 times perfectly. I tried to move and manipulate the optical cables to no effect. All is working fine on the bench. Air temp is about 66F in the work room.

I've been having these intermittent strobe failures for the last month, but it was always one or the other. Not both. I do have two Inon 330's which I use together in my wide-angle setup. 

Any theories about what is going on?

I don't know for sure but since you added new coin batteries have you tested them for charge. It sounds a bit like the batteries for optical cable might be wearing out, getting cold, after some time in the cold water and being used. If you swap in new batteries and check them for full charge you can determine it's not something stemming from the new batteries.

Good luck.

Jon

Yeah, I'd swap out the strobe trigger batteries too. Get a pair of Duracells and give them a go.

I had a similar problem a while back with intermittent strobe behaviour from very reliable strobes. Turned out my stock of "coin" batteries were no longer so fresh..... 

I tested the coin cells in the Trigger and they are both slightly over 3 volts.

I will get some new cells and try that before my next dive. I may swap out my optical cables as well just to remove that variable.

One test you can do on land to see if the strobes or their batteries are cold sensitive is to put new batteries in the strobes, test fire them, put them in the refrigerator for 30 and then 60 minutes, and test fire them again. This should tell if the batteries or circuit(s) fail when cold. 

If they fail when cold, you can then just refrigerate the batteries to see if the failure is in strobe circuits or the batteries. Separate and test each variable, one by one.

How long since you have cleaned the window for your strobe triggers?  I recall one intractable problem that was solved by pulling off the fibre optic sockets and cleaning the window.  After seeing that issue I started to use a blower bulb to displace water from the window as part of my housing cleanup post dive - basically to avoid water droplets drying out on the window. 

Swapping out cables is a good step - you may want to try the window cleaning first - so you do things one at a time and know which change solved your problem.

I assume you a regular cold water diver so if the batteries are fresh I can't see how low temperatures are suddenly coming into play as an issue.  Check the voltage of you coin batteries as well when you swap them out - lithium cells normally have excellent shelf life - are the ones in your trigger a known brand?

INON strobes certainly have a reputation for being easy to trigger - Backscatter a bit more sensitive to issues.

Two good suggestions. I have a wine fridge with a glass door, so I'll stick the strobes in there at perhaps 44F for a few hours and see if they still fire. I'll go a warm battery swap and try again with cold strobe.

Cleaning the optical pass through is another easy step to try out. I be sure to clean both sides well.

I'll report back with results.

Another possibility is that moisture inside the housing is condensing and fogging the trigger windows.  If so, one or two moisture absorbing packs might solve the problem.

On 1/7/2022 at 7:17 PM, ChrisRoss said:

 I recall one intractable problem that was solved by pulling off the fibre optic sockets and cleaning the window.

Good point, Chris! 

19 hours ago, Kraken de Mabini said:

Another possibility is that moisture inside the housing is condensing and fogging the trigger windows.  If so, one or two moisture absorbing packs might solve the problem.

I agree that could be possible, but why is this happening now after years of diving the same gear in the same weather?

I removed the flash trigger so I could clean both sides of the windows. I just used cotton swabs with isopropyl alcohol. I cleaned the optical sensor ports on the strobes as well.

I've also made a brand-new pair of cables from my supply of 2mm fiber. Comparing new to old with one end of each held to an LED source, the new ones do seem to be brighter. I'm not sure if that is just from clean cut ends or if the old fiber was crimped somewhere.

With the new cables in place, I will put the entire system in my very cold swimming pool this morning and see how it works after 20 minutes. I'll put a dive computer on it too to see how cold it is. I suspect it will be colder than Puget Sound's 48F.

I put the whole camera rig in the 44F swimming pool for about 45 minutes. I lowered it to the bottom with a dog leash.  Both strobes are firing just fine. Same batteries still installed in the strobes that stopped firing on the dives a couple of nights ago. Same batteries in the flash trigger. I fired off about 20 shots at the same power levels I usually use and neither strobe missed a beat.

Based on this I am eliminating batteries or cold temps as the cause of the problems. More likely the optical triggering pathway.

The new FO cables are the same as the old ones, off the same spool of cable. Generic 2mm single strand fiber purchased from Ebay. 

At this point I am guessing a combination of grime on the various optical surfaces (cable ends, housing window, strobe sensors) had accumulated to the point that the strobes were not triggering successfully. I'll be diving again on Wednesday and will have a true test in the field.

Dave, did you try to fire the strobes with the "old" cables?  Possibly just polish the ends might yield better results.

12 minutes ago, PhotoJunkie said:

Dave, did you try to fire the strobes with the "old" cables?  Possibly just polish the ends might yield better results.

There is no point. I have about 5 meters of the spare 2mm fiber so if a cable is questionable i just replace it. I reused the connectors so the old cables are not mountable any more.

My guess is that this is a cable problem. If the fiber you are using is single core, one break in it will be enough to reduce the optical transmission to a level that is not enough to trigger the strobe. This can also be the case with misaligned connectors. Any breaks could occur during storage, shipping or use. It can also be intermittent - as if the fiber either sides of the break or connector are momentarily aligned it may transmit sufficiently, if (even slightly) misaligned, it will not. 

As far as I am aware, there are no generic problems with the Nauticam trigger/Z330 combination. That kind of leaves the cable as being the most likely culprit. 
 

my 3 cents:

Every time i had encountered something like this with Z240s, it was always the cable and/or LED trigger, as per @adamhanlon suggestion earlier. First test without trigger, using camera strobe - this one is usually way more powerful. If it works, try new batteries in LED trigger, swapping cables etc. Also test without housing i.e hold cable direct to LED trigger. Broken cable might work like this, but once camera is in teh housing, it will receive even less light, due to that plexiglass plate between camera and the outside world. 

If making DYI cables, be careful how you cut the fiber optic...in my 4 cables made only one worked straight away, others needed a bit of polishing/re-cutting. If you are using simple scissors, fiber core might be scratched/squeezed and have this weird milky look. This, paired with LED trigger, which is not that strong, and housing plexiglas on the way, might result in not enough light passed through. Sometimes cable might be "semi" faulty - might work in certain position but slight move (i.e. during diving) and off it goes...again have one that works only under certain angle due to bad cut

As for batteries, in case of Inon''s it is important all are charged evenly and have similar capacity. So no mixing diff batteries or  new ones and 5 years old ones etc. Use "smart" charger with individual charging slots - no pairs/quadruples.

edit:

and don't use isopropyl alcohol on plexiglass...alcohol is deadly for acrylic like that. it will become brittle and crack

I made two dives today and everything worked perfectly. Between new fiber cables and some cleaning of the full light path the problem has been resolved.  Thanks everyone for your suggestions!

I'm having similar issues this week and came across this thread and am going to replace strobe trigger batteries and at least one sync chord on my Nauticam NA-D850 housing.  My question is approximately how long should the flash trigger batteries be changed?  The batteries in question were new one year ago and there have probably been 3,000 triggers since then.

Like the OP, this issue seems to happen during the dive, however to be honest, I try to limit the number of flashes on land to protect the strobes from over temp.

 I don't have access to a multi-meter so I can't test battery voltage.

Hi Redwing

I'm not using a Nauticam trigger but just to give you a quick readout, the TTL convertor for Subal (Made by UW-Technics) uses two CR2032 batteries and is rated good for 45,000 flashes or 1 year on standby.

48 minutes ago, TimG said:

Hi Redwing

I'm not using a Nauticam trigger but just to give you a quick readout, the TTL convertor for Subal (Made by UW-Technics) uses two CR2032 batteries and is rated good for 45,000 flashes or 1 year on standby.

 

Thanks.  That's a good benchmark.  The NA trigger uses two CR2032 as well.  Replacing the batteries at this point sounds like a good start.  Heading out to find a new sync chord and will clean the LED ports as well.

Yeah, battery replacement and and clean the ports is a very good start. Fingers crossed that does the trick. If you're using fibre optics, it's unlikely that it is those unless one if visibly broken.

I had a few problems with my trigger a while back, changed batteries, still had problems... switched to Duracell batteries and, bingo, problem solved. Cheap Chinese bulk batteries... why did I bother?