Flash clicks but does not fire any light ā likely trigger-voltage arcing?
Asked 1/4/2017
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2 answers
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My ring flash makes the normal discharge "click" when I press the Test button, trigger it from the hot shoe, or short the shoe contacts, but the tube does not emit any light. I opened the flash head and can see a spark when I press Test. The seller refunded me and let me keep it, so Iām wondering whether this is repairable.
What is the most likely cause of a flash that audibly discharges but never lights the tube? Could it be a dead flash tube, or is the trigger circuit more likely at fault?
Originally by Photography Stack Exchange contributor. Source Ā· Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
2
In your flash tube there is a large capacitor connected between the pair of big electrodes in the ends of the circular tube. When ready to operate, there is a large (lethally large!) charge waiting here to be discharged through the gas filled tube. The capacitor charge voltage (several hundred volts) is not enough to initially start the discharge.
To start the discharge a a very high voltage (10 000V or so) spike is applied to the trigger wire that is wrapped around the tube.
Your problem is likely that the wire electrode is too close to something. The trigger pulse shold not spark over anywhere outside of the flash tube. Find where it is sparking and try to increase the distance of the trigger wire to the other feature. A sharp end point sticking out from the trigger wire can also cause this wrong-way flashover. This external sparkover lowers the trigger voltage so it is not enough to ignite the tube.
As others say, when the unit is ready and has not flashed, it contains a lethal electric charge. This is for real, it is not just a routine consumer warning. Be careful.
Originally by user37167. Source Ā· Licensed CC BY-SA 4.0
user37167
7y ago
0
Generated from our catalog & community ā verify before relying on it.
Most likely the flash tube is not being properly triggered, rather than the main capacitor not discharging.
A flash tube typically has:
- a high-voltage capacitor across the tubeās main electrodes
- a separate trigger wire/electrode that gets a very high-voltage pulse to start ionization in the tube
If you hear the click and can see an external spark inside the head, the trigger pulse may be arcing to the wrong place instead of into the tube. In that case, the flash wonāt ionize and wonāt emit light.
A likely fix is to inspect where the spark is jumping and improve insulation/spacing so the trigger wire cannot arc to nearby metal or sharp points. A protruding sharp end on the trigger wire can also encourage stray arcing.
Be extremely careful: flash capacitors can hold several hundred volts and can be dangerous or lethal even after power is removed. If you are not experienced working around high voltage, do not attempt repair.
So yes, a dead tube is possible, but based on the spark and click, a misdirected trigger-voltage arc is the more probable cause.
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AI9y ago
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