HELP NEEDED! The WIRE around flash tube.

[553elx]

Hello everyone,

 

I recently bought a flash head that has four flash tubes in it, and is a part of a Broncolor Hazylight clone made by a Dutch company BEAM (no longer in business). There are four cables coming out of the head and each tube is rated at 3000 Watt-seconds. 

The photographer I bought it from told me that the two of the four tubes are not working, but  he didn't need that much power anyway. 

Upon examining the four flash tubes I noticed that on two of them the wire that goes around the flash tube and ends inside the third pin on the flash tube base  is broken on one and non existent on the other, apart from the small piece that goes into the third pin on the base. 

I know thar the three pins are a Plus, Minus and the third is connected to the trigger coil than initiates the gas inside the tube, so it can produce the strong flash. (or something like that)

MY QUESTION(s) IS(are): -What is the type of wire used for that purpose?

                                         -Where can it be bought?

                                         -Is there a specific thickness requirement for the wire

                                          or can a "close enough" is sufficient?

I plan on trying to add the wire to the two flash tubes that don't have it and make them functional again. 

Enclosed is a photo of a flash tube that is supposedly a good one, showing the wire around the flash tube. The ones without the wire look to be in better condition than this one pictured, no blackening around the electrodes.

 

Thank you in advance, any advice is much appreciated!

[rodeo_joe1]

The wire carries almost no current, but does have to stand up to a few milliseconds of intense heat from the flash tube. I suspect ordinary tinned copper wire might melt under the intentisity of the heat. Tinned copper is only rated to 180 C. 

It might be Nickel wire or something like that. 

Maybe contact Bron (are they still in business?) and see if they'll sell you some trigger wire? Because I don't think there's anything totally suitable on open sale in small economical lengths. 

If you opt for tinned copper wire there may be a risk of the wire melting into a sputter and welding itself to the glass of the flash tube. 

Another thing to avoid is contaminating the glass with oily fingerprints, which might etch the tube when fired. Wear nitrile or similar gloves when working on the tube, and if you do handle it with bare fingers, then clean the tube with alcohol before firing it. 

Edit. I see nickel electrode wire on sale at ebay. It's not cheap, about £1.20 per metre and a minimum of 10m order. 

Edited April 4, 2023 by rodeo_joe1

[553elx]

Thanks Rodeo Joe! 

Any thoughts on wire thickness? The original wire was very thin, but should i pay attention to the exact diameter or can I

eyeball it? I mean, is there a formula that I should follow (resistance, temperature. etc.), or is it not important?

Cheers

Milo

 

[rodeo_joe1]

Personally I would measure the diameter of the remaining wire with a caliper or micrometer. But as a rough guide: You want something thin enough not to obscure too much light, but thick enough to handle the heat. Not too thick that it can't be easily bent and manipulated around the tube as well. 

I just put a digital caliper to the trigger wire of an old Bowens strobe tube, and it measures 0.31mm diameter (about 28 wire gauge). But the Bowen's strobe is rated much lower than 3000 Joules. 

I'd say anything between 28 gauge (0.32mm dia.) and 24 gauge (0.51mm dia.) would be suitable. With 24 gauge probably being a bit on the heavy and inflexible side for easy manipulation. Nickel wire being quite stiff and not too flexible.

So going in the middle with 26 gauge (0.4mm dia.) might be a good choice. It depends what you can lay your hands on.

P.S. The resistance is quite irrelevant in this application. The trigger wire carries almost no current, but at a very high voltage. The several Kv electrostatic trigger charge initiates ionisation in the gas of the tube, which then avalanches into a full scale plasma sustained by the main capacitor charge. The job of the trigger is over in a few microseconds at most. However the plasma in the tube emits a huge amount of heat, and it's this heat that the trigger wire has to withstand. 

Edited April 5, 2023 by rodeo_joe1