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UltravioletPhotography

Flash tube holder PCB for Godox Wistro


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The flash tubes I ordered to UV-modify my Godox Wistro finally arrived after almost one months delay at the import/customs handling.

I installed the tube successfully using one of the alternative banana-plug typess I ordered at the same time as the flash.

 

The new tube deliver much UV-A, with a better UV / VIS ratio than my Canon 199A without front window.

 

The tube seams to survive so far even if it is driven way above its specifications.

However I have noticed that the tube got a lot of micro cracks all over.

This might be due to thermal stress, but also due to a combination with mechanical stress when mounting the lamp.

I think that is difficult to avoid without extra measures.

 

A way to improve the situation could be to add a suitably shaped circuit board. (PCB)

I quickly designed a pair with the correct hole patterns matching the one in the flash head.

Both fitting within the maximum 5cm x 5cm prototyping area from the PCB prototyping service.

The slits are to improve the insulation to the ignition pole.

post-150-0-76355900-1531575790.png

The holes in the board are slightly bigger than 4mm and should fit the connectors I used.

https://www.ebay.co....cs/112635627843

The PCB will reduce the mechanical stress if the threads from the flash tube are bent in a good shape before soldering and make the insertion into the flash head more controlled.

 

The Chinese PCB-prototyping service will deliver ten pairs of boards in a week or two, I hope. Then there will be a long stopover at the import process.

With some luck I'll get the boards

 

I will prepare one or two spare lamps with connectors mounted through PCBs, but will hardly have any use for all of the PCBs.

 

If any member is interested I can share the remaining ones. Just message me about it.

 

Andrea, I hope this is within the rules of the forum, because I do not intend to earn any money on this.

Otherwise please feel free to delete or strike and comment this last sentence.

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Ulf, it is very generous of you to offer the PCBs for no profit. We have no objection to this.
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After a brief look at my bulb I can confirm, there are some things like lots of micro cracks in the glass as well.

A quick calculation (p * v = n*R*T) and assuming a temperature of about 3000°C, when the flash strikes,

gives a pressure within the bulb of around 8 to 10bar.

So I think it is wise to use the flash with this bulb only with a protective cover in front of the bulb.

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enricosavazzi

[...]there are some things like lots of micro cracks in the glass as well.[...]

This is not a good sign. I believe one should stop using the flash tube if this happens.

 

In the best case, the cracks extend through the glass, air enters the tube and the xenon leaks out, and the tube stops flashing. It happened to me after overloading a small bulb a couple of times, with a flash unit probably less powerful than the Godox AD200. The inner surface of the tube also melted and modeled itself into a wavy surface. See picture at the bottom of this page: http://www.savazzi.n...dio_strobes.htm

 

In the worst case, the tube explodes and throws around thousands of small and hot glass bits.

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  • 1 month later...

The PCBs has arrived and work quite well.

 

My first flash tube has died. Three more to go.

It did not explode, but failed flashing every time.

Probably due to the events Enrico describe above, but not as violent as shown in the link at his site.

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