Pro Foto Acute B recycle time is now 12 seconds!!

[detune]

I have a little Profoto Acute B 600 generator, it's slowly in it's death throws I believe as the power switch (with Max, 4 and 2 as levels) only works on Max and 2 now and the recycle time has gone from quite fast (1 or 2 seconds depending on power) to 12 seconds.

There is so little information I could find using google so I'm reaching out here... looks like I have no choice but repair or a new one (so expensive!!!).

Anyone have any ideas on these kind of problems?

Funny thing is, once a flash is used, I can toggle the power switch and it charges instantly...!?

 

[TheFlyingCamera]

Sounds like you're looking at a pricey repair. Don't know the cause, but that's definitely not normal behavior. The Profotos are nice enough that they're worth repairing at least once, unless the repair bill comes out to the replacement cost. Look them up on ebay to see what a used unit runs.

 

[John Koehrer]

From your description that it recycles quickly once it's used, it is probably the main capacitor.
That's the one that provides the power to the flashtube. When they age they become hard to charge but once they've been recycled a couple of times they work properly(sound familiar) This is common with electronic flash both portable and studio.

 

[detune]

dam, yeah I figured it might be the capacitor, really it's such a tiny little box but it is amazing when it's working... just horribly priced.. and this sounds like a costly repair too.

 

[archphoto]

Leave it on for a coupe of hours, that will get the capacitor in a better shape.
Do this at least once every month untill you see an improvement.
Replacing capacitors is not a big deal for a repairman, getting the replacement can be if it is an off-one.
Contact the manufacturer.

Don't do the replacement your self: even after a full discharge quite a few Volts are left in them.

 

[tim_walls]

dam, yeah I figured it might be the capacitor, really it's such a tiny little box but it is amazing when it's working... just horribly priced.. and this sounds like a costly repair too.

High value capacitors aren't cheap, but they're not exactly unobtainium either - it ought to be a relatively inexpensive repair I'd have thought.

If for some reason a suitable replacement capacitor wasn't available, it is possible to reform caps with a fair degree of success relatively easily - I believe the military used to actually have dedicated capacitor reforming units which you can pick up at Ham events or military surplus, but all you really need is a variac. Like I say, I think it's highly unlikely to be necessary in this case, but it's rather common in my other hobby (classic computer equipment.)

If you know a friendly amateur radio enthusiast, this is repair they could probably do for you easily enough.



If the cap is on the way out though, it is best to get it fixed. Occasionally they can fail catastrophically (i.e. explosively) throwing corrosive electrolyte all over the rest of the board, turning what was a cheap repair into a pain-in-the-neck cleanup operation.

(I remember once at work we were working on some experimental communications hardware and had a big demo to senior management who were flying in the following morning; of course, just as we're doing the final checks on the demo kit the night before, a cap in one of the units decides it's going to explode in a really quite dramatic way. A late night followed... The demo effect is a wonderful thing!)

 

[resummerfield]

...... it is possible to reform caps with a fair degree of success relatively easily.....

I've always heard that a strobe that fails to recycle promptly needs to have its capacitors "reformed". I think this "reforming" can be accomplished by turning the strobe on and letting it "idle" for a day or so, with an occasional full discharge flash. But in my personal experience, I have not been very successful in "reforming" capacitors to get recycle time back to new specs.

Does anyone know the correct procedure for "reforming" capacitors?

 

[detune]

well I'll hopefully hear back next Monday about it and I'll post up here about the repair (cost and reason) so we can all learn from my bad luck There were no explosions, just a sudden slowness in charging and sometimes the ready beep would be a BEEEEEEEEEEEEEp instead of bip..!

 

[tim_walls]

I've always heard that a strobe that fails to recycle promptly needs to have its capacitors "reformed". I think this "reforming" can be accomplished by turning the strobe on and letting it "idle" for a day or so, with an occasional full discharge flash. But in my personal experience, I have not been very successful in "reforming" capacitors to get recycle time back to new specs.

Does anyone know the correct procedure for "reforming" capacitors?

Basically it boils down to connecting the cap up to a DC supply at its voltage rating, with a nice hefty current-limiting resistor in series. An unhealthy capacitor will leak current - in the worst case appear as a dead short - without the resistor in place this can lead to catastrophic failure.

With a CL resistor in place on the other hand, the current is limited to a safe level, allowing the oxide layer on the electrode to slowly re-form without the capacitor exploding.

The process may take hours or even days; you can tell whether or not it's finished by measuring the voltage drop across the resistor - a healthy capacitor will be leaking very little current, and so there will be little if any drop across the resistor.


It should be said though that reforming capacitors is normally only necessary if they've been in storage for a long time. In 'normal service' the small leakage current they exhibit normally is enough to keep the oxide layet healthy; it's normally only when they've been unplugged for a while that the layer deteriorates.

 

[resummerfield]

Thanks, Tim.

 

[John Koehrer]

- in the worst case appear as a dead short - without the resistor in place this can lead to catastrophic failure.

And is REAL exciting!

 

[Ralph Javins]

Good morning, Detune;

A different thought: Speaking as someone who worked in electronics in all of his "useful working years," I am not sure that there is a problem with the main storage capacitor that provides the power to the flash tubes.

You said that it works now only on "Max and 2," but not on "4." This is not a problem that I would associate with a failed or failing capacitor. You also said that there was a "sudden slowness in charging." I would not associate a deformed capacitor with a sudden change, especially if the change happened while in use. Problems with deformed capacitors normally show up after long periods of no use and storage. The main symptom will be that they will not hold the charge that they are supposed to have. You did not say that you did not get full light output.

A long increase in the charging time I think is a power supply problem or a control circuit problem. At least the part of the control circuit that monitors the power level of the capacitor does seem to be working still if it is waiting so long for the capacitor to charge up.

To me, the combination of those two symptoms point to a problem with either a section in the power supply or with the control system that sets the power level (Watt-seconds) of the energy stored in the capacitor for the flash tubes. One real curiousity is the fact that it does still work on "Max and 2," but not on "4," the middle power setting. Again, this sounds like more of a control circuit problem.

I am not at all sure what to say about the result when you turn the power switch off and then back on. More detail in the description of what happens here would be very helpful. However, again this could point to a control circuit problem.

I hope that there is a service center in Aukland, Wellington, or Christchurch. Fixing the problem may be very simple, but it may not be simple to diagnose. Having a schematic (a roadmap for electronics) would really be helpful.

My eldest son just sold his motel up in Paihia on the Bay of Islands.

 

[detune]

For anyone keen to know what it apparently was - a faulty isolation diode... I never woulda guessed....

Fixed for $230 (AUD) have only briefly tested it but judging by the speed it charges now, it must've been dying for some time now!!

 

[Ralph Javins]

Good morning, Doug;

Thank you for the report. I admit that I was curious. From your comments, it did not sound like a capacitor problem, but instead would be in the power supply or control circuit. Nice to know that the repair turned out to be fairly simple, and it was only 230 AUD.

I have performed a diagnosis by remote control over a telephone fairly often in the past, but I do not have a schematic for your flash unit here, and I did not know if you had a voltmeter and could work around the circuit with the needed safety considerations. I do recall one occasion involving a transcontinental telephone call for which the bill for that call came to $80.

Nice to know that DeTune Photography is back in full normal operation.

 

[detune]

You know what? Soon after, I did 2 shoots and it died again, this time they replaced the power board (like you mention?) and SO FAR SO GOOD... ha ha... oh dear... honestly I love the light given by this little tiny box, especially when combined with the D4 ring flash but due to the recent unreliablility issues, it's sapping my shooting mojo!! Being a random nomad around the world, I can't exactly carry spares!