Violet wand - Page 1
Forum section: electronics / repair

author: gblades
author_rank: Contributor
timestamp: July 26, 2016, 02:19:09 pm
content: Something a little different...Has anyone ever reconditioned a vintage violet wand?I said I would take a look at this one for a friend. The capacitor measured 0.8uF and once I cleaned off the contacts controlled by the electric magnet it started working. The output power was low and then the contacts started arcing occasionally. I suspect the contacts are pitted so will need removing and either replacing or smoothing off.I have no idea what the value of the old wax wound capacitor should be though.

author: German_EE
author_rank: Super Contributor
timestamp: July 26, 2016, 06:34:52 pm
content: What is it? A UV light source?

author: Jwalling
author_rank: Unknown
timestamp: July 26, 2016, 06:35:39 pm
content: I'd never heard of such a thing, so...https://en.wikipedia.org/wiki/Violet_wandYikes! Please tell me I'm wrong!Jay

author: gblades
author_rank: Contributor
timestamp: July 26, 2016, 06:48:08 pm
content: I am sure they were known as violet wands and violet rays. The term I used seems to be well known for a more modern version.If you look at the photos you can see it is a vintage piece of quackery medical equipmenthttps://en.m.wikipedia.org/wiki/Violet_ray

author: Gyro
author_rank: Super Contributor
timestamp: July 26, 2016, 07:02:48 pm
content: That's basically an old fashioned induction coil you have there for powering the tube. The capacitor is across the contacts to prevent sparking and boost the output (basically by absorbing the emf across the opening contacts and creating a resonant circuit). The slightly rusty looking mess in your third photo is a bundle of soft iron wires, used as the magnetic core, for the same eddy current suppression reasons as the laminated cores on transformers.If you are getting intermittent arcing of the contacts then the connections to the capacitor (or the capacitor itself) may be intermittent. It's also possible that you might be getting intermittent insulation breakdown of the secondary winding - it would be best to operate it with a load, ie. the tube.P.S. Just had a scary thought, what are you powering it with?

author: Jwalling
author_rank: Unknown
timestamp: July 26, 2016, 07:06:03 pm
content: Quote from: gblades on July 26, 2016, 06:48:08 pmJay

author: gblades
author_rank: Contributor
timestamp: July 26, 2016, 07:15:54 pm
content: Quote from: Gyro on July 26, 2016, 07:02:48 pmIt is mains powered. Let's just say when I tested it everything was sitting on something metal which was very well grounded and nowhere near any sensitive electronics. The only part I touched was the plastic dial!

author: Gyro
author_rank: Super Contributor
timestamp: July 26, 2016, 07:33:02 pm
content: Youch! You're braver than I am.Looking at the plug, it may well be that it dates from the days of AC/DC mains. I really wouldn't risk of powering it from the mains today. You have no idea about the quality / deterioration of the insulation (coil primary-secondary), that capacitor may blow up unexpectedly (and probably spectacularly!), no fusing, cable strain relief etc.In all conscience, I really think it really is one for the 'curiosity display' rather than being plugged into the mains.It probably wouldn't be too difficult these days to build a small high frequency inverter to safely drive the wands.Edit: Anyone else notice the slightly dodgy sounding product logo!

author: CJay
author_rank: Super Contributor
timestamp: July 26, 2016, 07:39:17 pm
content: Ouch, whoever pointed out the AC/DC mains has a point but there's one other outside possibility, the mains lead might also be a resistor, they used to fit droppermains cable to radios 'back in the day' and many a fire was caused by people shortening the cable.

author: JacobPilsen
author_rank: Regular Contributor
timestamp: July 26, 2016, 07:47:01 pm
content: Could be seen in movie:Cutting_It_Short(?SSR 1980).