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Author Topic: Mercury vapour advertising tube  (Read 24349 times)

Offline Derek R

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Mercury vapour advertising tube
« on: October 31, 2003, 09:07:00 am »
I am new to this forum but feel maybe you are just the good folk who could help me with my current project.
In the 1930s a friend made his living hawking display signs around London for use in the windows of hairdressers or shoeshops. A neon-filled tube shaped to form the outline of a stiletto heeled shoe was the red option, the outine of the head of a neatly coiffured young miss was the blue one. With the tube plugged into the top of a metal case of about 8" square they were designed to run from 240V mains and looked spectacular in front of a black velvet curtain (he says).
I have inherited a head which is simply a formed length of (about) 10mm diam glass, capped at each end with a metal cover and containing a small amount of liquid mercury.
The ends are parallel and about 3" apart and simply drop into a pair of Tufnol (Paxalin or SRBP) tubes sunk into the top face of the box. The other end of each tube has a spring which is then wired to the output tappings of a transformer.
Up until a couple of years ago it worked but failure was due to a short in the winding of the TX (I guess on the HT side) and I am now looking for a replacement. The state of the insulation on the windings is less than perfect so deconstructing and repairing at the area of the short is not on. There is no indication of any rating on the device other than a hand-scrawled "2000" that can just be made out. Does this mean a 2kV secondary?
Sadly my knowledge of tubes runs out at that point. Is this a common beast? What voltage is needed to strike a discharge? Could anyone help me with a spec for a replacement TX; what Vout and at what current? Being retired I no longer have access to the kit to have a bit of a play around (if that's the correct term for HT)to find out empirically. I have the feeling this is a problem best solved through experience rather than getting out the text books.

If lengths & volumes are needed to do any necessary sums I will try to post some pics to help. I am not sure how that is done as this is my first forum but nothing ventured..
Despite some work being needed to improve the HT side safety I think it shouldn't be too difficult to restore this thing of beauty to its original splendour. It would look cracking amongst our other art deco furnishings and deserves another chance to shine.

Incidently, if ayone has any info who made it originally - London, early '30s - then that would be a tremendous bonus.

Offline James

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Mercury vapour advertising tube
« Reply #1 on: November 09, 2003, 10:58:00 am »

The transformer it needs is probably nothing special - I would reccomend taking it along to a local neon sign fabricator.  For a reasonable price they could probably sell you a modern electronic transformer to replace everything inside your box.  2000V sounds about right, but they will be able to match your tube up with a transformer just by looking at its length and tube diameter.  They don't have to be critically matched, a slightly bigger or smaller transformer just makes the tube glow brighter or dimmer and has little influence on lifetime.

If you can't find a neon sign shop, give Tunewell Transformers in Edmonton a call and they should be able to help you out with a whole new unit made specifically for lighting neon or mercury tubes of this type.  They're the worlds leading manufacturer of transformers for neon tubes.  By pure coincidence they are based in the old buildings of Sir Jules Thorn's first ever lamp factory in England!


Offline Tim

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Mercury vapour advertising tube
« Reply #2 on: November 12, 2003, 06:37:00 am »
Hi Derek,

Welcome to the bulb forums. ?I would love to see a picture or two of this sign. ?Signs like this interest me greatly. ?Could you email some pictures to me, or upload them here to the board? ?My email address can be found here:

Instructions regarding attaching pictures to your messages can be found here:
<***Broken link deleted***>


Kilokat's Antique Light Bulb Site
Mountain Dew Collectibles, Volume I
« Last Edit: December 16, 2004, 06:21:18 pm by tim »

Offline Derek R

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Mercury vapour advertising tube
« Reply #3 on: November 24, 2003, 04:36:00 am »
Many thanks for your replies.

James - this looks very useful. I assume this Edmonton is that just up the road from Tottenham, in which case luck appears to be with me as that's not far away.
Coincidently I once attended a week-long course at Swansea Univ entitled "how to build a computer in a shoebox" where I spent 5 days inputting hex code into a 6502 just to get it to illuminate on a 7-segment display the results of single-digit multiplication. I turned my back for 30 years and look what happened! The view from the twin accommodation blocks over the bay to Port Teapot beyond is not to be forgotten and I've returned to Mumbles for holidays since.

Tim - I am trying to tease details of the manufacturer from the fragile memory of an aging friend but have high hopes of success. My feeling is that it was a one-man show who employed a sales force working on commission.
I only have the one example of the mercury vapour tube in the shape of a head profile and know of no surviving neon shoe. I shall of course provide pictures; all I need to do is overcome the old dog/new tricks barrier associated with posting. If it proves too much for me may I e-mail them sraight to you, or mail a CD? My aim is to provide a photo of a fully working device - about Easter maybe!

Regards - Derek

[This message has been edited by Derek R (edited November 24, 2003).]

Offline Derek R

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Re: Mercury vapour advertising tube
« Reply #4 on: October 08, 2005, 03:01:39 pm »
Please excuse the slight delay of 23 months but I have good news. Fred's Lady is now in my sitting room on a suitably art deco table and lights up in full majesty at the flick of a switch.
In order to acheive this I had to come out of retirement and take up work in the electronics industry again just to have access to the necessary test kit. With the help of a very skilled artisan - well, he took over the project really and applied his varied techniques gleaned during 40 years in the business. Luckily this meant he was old enough to be fully au fait with rebuilding transformers.
The problem was not as expected a short on the HT side but a break in a soldered joint deep within the secondary winding. The state of the insulation was remarkable considering the age and a few deft touches with an iron affected a repair. Without my mentor I would not have known about E and I plates or the practicalities of dismantling an HT TX, let alone the reassembly. It was a magic moment when the power was switched on and the light shone.
As you may imagine the raw mercury vapour light is rather cold although the phosphor coating the area of the hair is less harsh. It takes quite some time for the intensity to settle down as the vapour pressure stabilises and the plasma(?)   becomes more uniform.
The only downside is that the TX plates are not as tight or flat as once they were and she gives off an audible 50Hz (mains) buzz. Has anyone experience in DIY silencing of transformers? I have worked in the developement of superconducting magnets for MRI use and am familiar with parrafin wax dampening. Is it worth trying this at home or would I be better off popping down to my local transformer maker and getting it vacuum impregnated with varnish?
I do have photos. I took some during the restoration process and can take more of the finished article if anyone is interested. I am slowly getting to grips with computer photo-hosting and am prepared to place all the info I have on an MSN group site. I am not egotistical enough to do this if nobody will ever see it so do please let me know if there is any demand. (I'm still not sure if Fred's Lady comes under the perview of this site). The attached snap gives an indication of her beauty, and the untidiness of my bench.

I'll check for replies regularly and promise this time that any required action WILL take place before Easter.

...and no, she's not for sale.


Offline Tim

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Re: Mercury vapour advertising tube
« Reply #5 on: October 11, 2005, 09:45:01 am »
Hi Derek,

I didn't forget about this topic and I've been wondering if you have had any progress in restoring "Fred's Lady".  Congrads, she looks good!  The project sounds like a labor of love.  If you do decide to post information on a website detailing the progress, be sure to let us know and I'll post a link to it.