Film-Tech Forum ARCHIVE: What's the purpose of the chain hanging from a Xenon bulb?

This is topic What's the purpose of the chain hanging from a Xenon bulb? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brad Allen (Member # 470) on 11-21-2005, 01:27 AM:

Subject says it, my kneisley's is the only one's I've seen this in. What is the point of the chain. I've always just blindly put it back on when changing a bulb.

Posted by Richard Hamilton (Member # 321) on 11-21-2005, 06:19 AM:

quote: Brad Allen
I've always just blindly put it back on when changing a bulb.

Does that mean you keep your eyes shut when you change bulbs? [Wink]

Posted by Marin Zorica (Member # 1716) on 11-21-2005, 08:04 AM:

Can you described little more about that "chain", maybee is volfram wire for faster ionization of xenon gas you thinking on?

Posted by Gilbert Travin (Member # 2138) on 11-21-2005, 08:17 AM:

I think Martin is right : this "wire" facilitates bulb ignition.
Even cold, there is high pressure xenon into the bulb >>> danger !!! Use the protection mask and gloves !!!
[thumbsup]

Posted by Gordon McLeod (Member # 33) on 11-21-2005, 08:36 AM:

At one point kniesly felt it helped eliminate a capacitive effect in the lamp during ignition

Posted by Brad Allen (Member # 470) on 11-21-2005, 12:54 PM:

Sure Richard, I've performed it so many times I can do it with my eyes closed. [Eek!]

It's a ball chain, just like the type you would find on a light pull chain.

Posted by Frank Angel (Member # 248) on 11-22-2005, 05:13 AM:

quote: Gordon McLeod
At one point kniesly felt it helped eliminate a capacitive effect in the lamp during ignition

Does it?

Posted by Louis Bornwasser (Member # 3063) on 11-22-2005, 05:43 AM:

With the nichrome "gimmick capacitor" wire tied to every xenon bulb, it is probably no longer needed. Just a vestige from former times.

As regards the old Kneisley; another trick is to insulate the bottom of the igniter from the case using plexi or fibreglass. Arc overs there are common when the igniter fires. It still arcs in the bulb, but intensity is reduced.

This is a lamp that can be made to run very well enough, but it takes a bit of labor to do so. Whenever we sell one used, we replace the meter, shunt, capacitors in the power supply, add the igniter spacer and upgrade the teflon bushing. I would never sell one "as is." Louis

Posted by Marin Zorica (Member # 1716) on 11-22-2005, 11:59 AM:

Louis, i think is wolfram wire on osram bulb's, i know because on poster i got with bulb it says wolfram!

Maybe chain is for bulb arc stabilization like on carbon arc systems.

Can you upload picture of it?

Posted by Brad Allen (Member # 470) on 11-22-2005, 01:16 PM:

Marin, I will get a picture as soon as I can remember to take the camera along. [Smile]

Louis, or anyone else, is there a reason one couldn't just by- pass the shunt all together and take it out of the loop?
I use a DC clamp on meter for amp adjustments anyway.

Interesting about the plexi addition, any thickness will do I assume? And I assume the placement of the plexi is to be between the bottom of where the entire Telsa coil assembly meets the metal case?

Posted by Louis Bornwasser (Member # 3063) on 11-22-2005, 03:15 PM:

yep

Posted by Richard Fowler (Member # 893) on 11-22-2005, 03:56 PM:

White plexi or Phenolic board does the trick which stands up to the U.V. from the bulb and is more flame resistant. The front bulb support has an insulator that deteriorate with age which should be checked.

Posted by Frank Angel (Member # 248) on 11-22-2005, 08:03 PM:

quote: Brad Allen
It's a ball chain, just like the type you would find on a light pull chain.

That's Kneisley's emergency igniter....if the bulb fails to lite, you just pull the chain to turn it on. [Big Grin]

(Sorry, I couldn't resist).

Posted by Brad Allen (Member # 470) on 11-24-2005, 01:13 PM:

The chain....

Posted by Tim Reed (Member # 137) on 11-24-2005, 01:38 PM:

What Gordon said.

Posted by Ken Lackner (Member # 1002) on 11-24-2005, 03:01 PM:

That's interesting. I used to operate Xenex II's and I've never seen that chain. I can't quite tell from the picture...what is it attached to?

Posted by Dominic Espinosa (Member # 2122) on 11-24-2005, 03:14 PM:

Brad,
We have the same lamphouses you do, ours however do not have that chain. I've noticed no negative effects in its absense.
If that is any consolation.

Posted by Monte L Fullmer (Member # 2797) on 11-24-2005, 03:26 PM:

True, I have ran a Xenex this summer at a drive-in (which didn't have this chain and I was running a 3k bulb) that this is the first time that I've heard of that chain effect.

Still quite interesting that this concept was conceived-probably due to that the bulbs at that time of lamphouse manufacturer, didn't have that capacitive wire attached to the bulb as they are now.

-Monte

Posted by Frank Angel (Member # 248) on 11-25-2005, 12:41 AM:

Hence a chain reaction [Roll Eyes]

Posted by Tim Reed (Member # 137) on 11-25-2005, 12:57 AM:

quote: Ken Lackner
I used to operate Xenex II's and I've never seen that chain.

The chains were in original Xenex's, in the mid-70s.

Posted by Brad Allen (Member # 470) on 11-25-2005, 12:51 PM:

quote: Ken Lackner
That's interesting. I used to operate Xenex II's and I've never seen that chain. I can't quite tell from the picture...what is it attached to?

It's not attached to anything. It just hangs.

Posted by Michael Schaffer (Member # 1204) on 11-25-2005, 10:50 PM:

How come it doesn't short the cathode to the lamp house?

Posted by Daryl C. W. O'Shea (Member # 1303) on 11-26-2005, 12:27 AM:

Quartz isn't usually conductive.

Posted by Marin Zorica (Member # 1716) on 11-26-2005, 01:34 AM:

Ok isn't connected to anything - that's mean it has no electrical function like arc stabilization (i bet no bulb have this like carbon arcs) and is not for for faster ignition, this is wolfram wire...

It's may bee somebody put just like that with no special reason or may bee come with bulb and someone forgot to move it from bulb?

Posted by Michael Schaffer (Member # 1204) on 11-26-2005, 02:57 AM:

OK, I see now that it's not touching the cathode end piece. When I looked at the picture without my glasses I couldn't see that the back part of the lamp was clear with the electrode inside. Isn't the same purpose served by the little wire found on most lamps though?

Posted by Monte L Fullmer (Member # 2797) on 11-26-2005, 03:58 AM:

Yea, if I remember that the early xenon bulb didn't have the wire being wrapped around the anode end of the bulb and attached at the cathode end.

These early bulbs were a bugger at times to ignite-let alone love to explode when they were newly put in the lamphouse. There used to be a warning sheet in the box (Osram) of potiental explosions in the first half-hour of operation.

Posted by Louis Bornwasser (Member # 3063) on 11-26-2005, 09:51 AM:

Yes, the vestige of an earlier day. (OK to lose the chain with modern bulbs) Louis

Posted by Gordon McLeod (Member # 33) on 11-26-2005, 10:45 AM:

Part of the purepose was also to reduce the effect of the coating on the reflectors that with some brands of lamps influenced ignition

Posted by Michael Schaffer (Member # 1204) on 11-27-2005, 03:36 AM:

How?