Film-Tech Forum ARCHIVE: Kneisley Ignitor VERY loud suddenly

This is topic Kneisley Ignitor VERY loud suddenly in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brad Allen (Member # 470) on 11-29-2008, 03:17 PM:

This problem first raised yesterday, at start of film the lamp did not ignite, but the ignitor was stuck "on".
And the ignitor could be heard 20 feet down a hallway through a closed door.

They are pretty certain noise is coming from the lamphouse.

Shut down everything, then took 3 more attempts to get lamp to light correctly, but each time the ignitor was very loud.

Upped the amps to the bulb by 5amps, and that so far has cured the lamp igniting issue. Lamp has 800hrs on it. But the ignitor continues to be MUCH louder then the other two Knielsey's.

2000watt Osram bulb, Irem rectifier.

What should I be looking for as the cause? I assume voltage jumping to something it should not be?

UPDATED: OK, lamp still is not lighting well, had to remove diode/cap from autoignitor then used the manual ignite button and took 5 attempts to light bulb. Amperage of bulb when running is 68 amps.

Now I'm thinking the bulb is going south...

Posted by Louis Bornwasser (Member # 3063) on 11-29-2008, 08:56 PM:

Check no-load voltage first. Louis

Posted by Gordon McLeod (Member # 33) on 11-30-2008, 08:04 AM:

The autostrike in the Xenex is very simple it will stay energized as long as the no load voltage is above its thresehold
The rectifier will not drop its noload output till the lamp draws its operating current so in this case the ignitor will continue to fire until it either burns out or the lamp lights
Raising the tap on the rectifier will usually raise the output noload voltage slightly and may be enough to get it over the hump of not wanting to light

Posted by Brad Allen (Member # 470) on 12-02-2008, 09:00 PM:

To finish this up.

Found the magic Kneisley chain had slipped back almost against the back bulb connection...thus voltage arcing to chain and to cabinet.

Anyone else still bother to use the magic chain?