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Author Topic: Ignitor question, spark gap Marc Jones Film Handler Posts: 82 From: Elizabethtown, KY Registered: Jun 99 posted 03-17-2003 08:26 PM                     What is the purpose, and how would you tell if it is correctly adjusted. One thing I notice with a knisley L2000 lamp house. I had problems one night with igniting a bulb with approx 1000 hrs, While tring to ignite you could see the spark in the spark gap, but no high voltage or sparking across the bulb. Just curious if the spark gap would possibly be problem or out of adjustment.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-17-2003 09:02 PM                     Marc, If you fire it with the room lights off you'll probably see it arcing to the mirror at the rear....This is very common. Try looking at the insulator that goes through the mirror and see if its gotten a bit crispy at all. Things tend to conduct when they turn to carbon. If the inslator is ok you may ahev a bad lamp, or a lamp which has the ignition wire too close to the mirror. Get the lamp manufacturers permission BEFORE you remove the nichrome wire. If you don't find any wire there then thats also another possibility. A lamp with that many hours sometimes needs the wire to help conduct the HV and then ionize the gas. If the lamphouse fires the ignoitor automatically when you turn it on the rectifier would seem to be ok....BUT the relay pcb in the Irem rectifiers does fail once in a while. Mark @ CLACO  |  IP: Logged Jon Bartow Master Film Handler Posts: 287 From: Massachusetts Registered: Nov 1999 posted 03-17-2003 10:25 PM                     Marc, the L2000 ignitor has a factory preset spark gap, don't worry about it. Mark is on the right path, I'll bet the plug that goes in the back of the reflector is grounding out the bulb. (very, very common with that lamphouse) Is that plug held in place by a rubber o-ring or a coil spring? You should order a replacement, they are very cheap. Jonathan  |  IP: Logged Marc Jones Film Handler Posts: 82 From: Elizabethtown, KY Registered: Jun 99 posted 03-17-2003 10:38 PM                     The insulator piece thru the reflector has been replace, I had that problem before so all of my knisely lamps have the teflon looking piece. The rectifier is a Kniesly also, So you can rule out the relay board. Just the thing I was thinking of was if the voltage is jumping across the spark gap then I would figure that that was the path of least resistance and my voltage is flowing in that direction. So my thought would be if the spark gap was opened then it would arc across the bulb. If this makes sense. I also verified that I had good connections on both ends of the bulb, so I can rule that out. Thanks for the responses  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 03-18-2003 12:17 AM                       FWIW, the spark gap doesn't matter, as long as there is a gap. It's a spark gap oscillator in actuality. Changing the gap width (without making it so wide it won't fire, or so close that the ends practically touch) really only changes the fundamental frequency of the tank circuit it is a part of.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-18-2003 09:52 AM                     changing the frequency can have other effects. If it get too high the HV will start to tend to fly off more to other items in the lamphouse If it is too low then the radiated noise into soundsystems can get worse. Also some of the HV caps don't particularly like too high of frequency It is normally tuned to about 30KHz according to an old Osram report  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 03-18-2003 10:41 AM                       Didn't know that, Gordon. I figured it probably had some effect, but was probably minute or negligible. I can understand caps having reactivity issues at higher frequencies, but I don't know how much the frequency changes with the gap width, either. I've made igniters before, using spare parts in an emergency. For the spark gap, I just placed two wires a short distance apart. As long as it oscillated, it fired.  |  IP: Logged Marc Jones Film Handler Posts: 82 From: Elizabethtown, KY Registered: Jun 99 posted 03-18-2003 11:25 AM                     Thanks now I know, just curious what/where would you get a scope probe to handle the voltage. Thanks for the info  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-18-2003 01:01 PM                     If you change the arc gap size it just changes the frequency of the oscillation. They work like an old arc gap transmitter. Mark @ CLACO  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 03-18-2003 04:00 PM                       Precisely.  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 04-14-2009 01:20 AM                 It has been 2218 days since the last post.  |  IP: Logged Eric Robinson Jedi Master Film Handler Posts: 538 From: Santa Rosa, CA Registered: Jan 2005 posted 04-14-2009 01:20 AM                     Couldn't someone just use a neon sign transformer to create a spark in the bulb, I have one with a 25K secondary that is able to conduct a good length through air. Am I missing something?  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 04-14-2009 10:43 PM                     Marc- I have several Knisley lamphouses and as others have said, this is not an uncommon problem with them. As the bulb ages and becomes a bit harder to strike, you'll find that very often the negative terminal of the bulb is arcing to the metal frame that supports the mirror right at the point where the ass-end of the bulb goes through the hole in the center of the reflector. The problem is worse in areas with high humidity. In several of my lamps, I've fabricated a teflon collar which pokes through the mirror hole and provides additional insulation. I'm not sure if the lamps originally had an insulator there or not, but the lamps I was working with had none. However, I see that a shipment of 3 new Knisley L2000's that I just received, but haven't installed yet, come with an insulating collar similar to the ones I made.  |  IP: Logged

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