Function of component in flash tube trigger circuit?

It is, I believe, the trigger transformer. A low-voltage pulse is stepped up to trigger the flash.

If you dont like small put it in a larger box, manufacturers are not known for extragance and they tend to use the minium specs components. Perhaps you may like to reword the question ?

As per the other poster, it's likely the trigger transformer. They're usually quite small, as they have few primary turns, lots of secondary, and since the wire is quite thin (impedance isn't a problem as they don't supply any appreciable current), they end up quite small.

It is definitely the trigger transformer. Typically a few primary turns, a few hundred secondary turns, takes 150 V from a capacitor discharged through the shutter contacts or an SCR, and produces 10kv or more to the trigger wire or reflector of the flashlamp. But essentially no current.

--- sam | Sci.Electronics.Repair FAQ:

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What seems strange is this transformer must be half or third of the volume of the ones in compact camera flashes but the tube is perhaps 100x the volume of the tube in one of those cameras (1cm diameter, 20cm long). Don't know the joules rating of this one, a large studio flash unit, but 530V standing voltage. Perhaps 2m of wire wrapped around the flash tube, as trigger, all in all seems inadequtely tiny in comparison.

I think I'll try 2 camera ones in series with 100 ohms initially to try and localise why not triggering. I may try subbing this tiny stepup transformer with one 3 times the size from a compact camera, as am wondering if it could be internally arcing actoss turns.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

The size is virtually irrelevant, as Sam says, almost no current is required. I've used a tiny trigger transformer salvaged from a disposable camera to trigger a huge (about 8" long) 1KJ flash tube. Some are bigger, some are smaller, it has more to do with age, manufacturing process, and the need for compactness.

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Is it possible to have a non-functional tube with no signs of problems , like the black patches on the ends of a fluourescent tube that is on the way out.

This one looks perfect other than the glass is a bit dirty on the outside, because the distributed trigger stops any cleaning. Not been dropped, no cracked glass, no odd looking deposits on the elctrodes or on the inside of the glass.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Yes, it's possible, but not terribly likely. You should be able to test it by applying voltage to the tube and using a piezo flame igniter to trigger it.

What is the problem, this is just a standard trigger transformer. Normally the capacitor is charged up to 150V to 250V and then when the SCR is turned on the 150V to 250V is applied across the primary of the tranformer. The transformer steps up the voltage ( turns ratio about 20:1) and generates a trigger voltage of 3 to 5 kV. This ionises the gas inside the flash tube, and the resistance (impedance ?) is reduced sufficiently for the 150V to 250V to strike across the tube.

The transformer is small because it only handles the tiny power to initiate the flash in the first place. It does not handle the 50 J or whatever that goes through the tube.

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I like that suggestion, just connect the arc pin of a piezo gaslighter to the trigger wire, when the standing voltage is across the tube- pure, minimilist test.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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This should be the trigger transformer. I have rarely seen these go bad. I have had lamp and capacitor failures on flashes.

The output of the trigger transformer is normaly a few thousand volts at extremely low current. The trigger pulse is usually in the order of about 50 to about 500 ns depending on the flash output power demand.

--

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-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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How do you test for lack of air in a xenon tube? Putting a neon bulb and dropper over the trigger transformer gave plenty of strike even in room lighting. I've an old reserve piezo gas lighter that the metal grounding barrel on the end falls off, ideal for testing this tube, but no flash over. Trying to find a medium size xenon tube I have somewhere or will try with a couple of copmpact camera xenon tubes or one removed from a xenon burglar alarm flasher, both with some sort of droppers, later today

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

With 2 compact camera xenon tubes in series and a 1K, 10W dropper and the 2 camera trigger surfaces connected together to the existing trigger circuit, it will reliably trigger the tubes to rather unstable continuous light , until I switch off , as 10W is not enough for continuous dropping. I once triggered with the piezo gaslighter, proper trigger disconnected, but didn't work the next few times. The owner reported it would intermittently not work before giving up totally , so I assumed it could not be a tube problem , well not gasifying anyway. What can have gone wrong with the original tube ? Does the standing voltage required to strike increase with age ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Basically that's it. Put 300-500 VDC across the tube and apply the output of a Piezo lighter to trigger wire or reflector.

Or, if you have something like a helium-neon laser power supply or neon sign transformer or oil burner ignition transformer, you can apply its output through a ballst resistor to limit current across the flashlamp. It should ionize.

--- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Tubes can leak. :)

--- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

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Could you have a very marginal leak over a couple of months leading to intermittant problems ? I would expect any leak to manifest itself as total failure in hours at the most.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I've now tried 2 xenon beacon tubes in series and it works every time on full or reduced settings. Also works every time with the piezo gaslighter when iys ground plate is connected to the flash unit ground

I was always told that the clap of thunder was due to air refilling the gap after being punched through by the lightening plasma arc. That cannot be the reason for the pop when such xenon tubes fire as there is no air inside them , why the pop?

What sort of power coming out as light in both cases. Unknown original tube of 10mm diameter , 200 mm long

Supply is from 2 seriesed 1000uF capacitors with 300V on each The beacon tubes are rated for 250V min , 500V maximum, nominal 400V maximum energy input per flash: 45W /second, maximum flash rate at maximum input power: 100/min

There is strike defeat, while recovering, sub-circuit and recovery time is about 1/3 sec, don't know what it is with the original tube.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Sure, you could have a leak small enough to take years to leak in enough air to cause failure, it also may only leak under the stress of the tube firing.