Film-Tech Forum ARCHIVE: Kneisley Xenex II lamp holder meltdowns

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Posted by Peter Mork (Member # 1336) on 11-01-2004, 12:42 AM:

I run four Kneisley Xenex II (2000 w) lamphouses. They aren't my favorite but I am stuck with them. At one time or another they have each had the same problem: the alignment will go out and on investigation I will find the white plastic part of the cathode holder undergoing a partial meltdown and the rear end of the lamp sagging. Obviously it's getting much hotter there than it should. I check the internal and exhaust fans and they seem clean and okay.

I've noticed that the cable attaching to the holder gets blackened at the connector, and have tried filing off the carbon and reattaching. But sooner or later it will happen again.

Now I'm starting to suspect the cables just deteriorate over time and start arcing internally. Is this possible? Pulling back the insulation, the cable just looks dirty.

My boss insists the current must be set too high. Since the amp meters on the rear of the housings have all failed, I can't tell. But the lamps are running at a good brightness and I hesitate to muck with it.

Any ideas?

Posted by Rich Ferrando (Member # 2056) on 11-01-2004, 01:23 AM:

We had the same problem with one of our Xenex II's (2000 watt as well) in May. We traced it to two problems.

1) Even though the blower was fairly clean and seemed to be functioning properly, we discovered that it would occasionally "slow down" during operation, and sometimes even stop without triggering safety systems and shutting down the lamphouse (turned out that a "previous know-it-all" bypassed it.)

2) After installing a new blower that ran magnificently, we found that the lamphouse housing would still get extremely hot to the touch. Our local tech guy tested the air flow in the lamphouse, and discovered that, though the blower was working great, the roof exhaust was not pulling nearly enough air through (I believe it was 100 cfm - maybe lower - instead of the mandated 300 cfm.) This was because two of our 2000-watt lamphouses were connected to the same roof exhast, which cut the flow significantly.

Our other two Xenex II's (a 2k and a 3k) have not had the meltdown issue, though they seem to be a slightly different style than the one that did fail on us, in that the two that have not had the problem have a deeper paint color than the one that did fail. I don't know if this is just a superficial paint difference, or if it signifies a different manufacture series where quality went down (or up) a notch.

Our 3k Xenex II is in an older part of the booth, and is connected to its own exhast system, and the surface barely gets warm during operation. (Actually, I think its connected to both the exhausts that used to run on two lamphouses when this was a single-screen changeover house.)

Posted by Michael Schaffer (Member # 1204) on 11-01-2004, 03:13 AM:

We have one location with 8 Xenex II and even though the problems described by Rich don't apply to the location, we still have those meltdowns and cable deteriorations once in a while. I think it's just crappy hardware and design. We learnt to live with it. There are always some cables and adapters in the location, and we check the parts for wear to avoid catastrophic meltdowns.

Peter - get yourself a clamp amp meter. Make sure it can also read DC because the cheaper ones often only do AC. For instance, I have this Fluke current clamp. It is a very useful tool, and if you suspect you have inadequate current settings, it is well worth the expense. It also comes in handy when you have a diode problem - you can quickly test the diodes in a power supply without disconnecting one end because checking the leads of shorted ones will read much lower than the functional diodes, and open ones won't read any current.

Posted by Gordon McLeod (Member # 33) on 11-01-2004, 07:23 AM:

Make sure the end of the lamp is properly clamped down in the holder as any loosness to that connection or the cable will cause it to overheat and melt down

Posted by Mark Gulbrandsen (Member # 72) on 11-01-2004, 07:38 AM:

Roof exhaust at each lamphouse needs to be a minimum of 600 cfm. I normally spec a 980 cfm (Static pressure) Grainger exhaust blower. With the proper amount of roof exhaust the internal blower has little to no meaning at all, especially in a Kneisley!! Also make sure that the roof blowers are running in the proper direction as iif they turn the wrong way they will have very little suction as compares to running them the correct way! I've encountered MANY blowers that were never checked for proper rotational direction.

Mark @ CLACO

Posted by Richard Fowler (Member # 893) on 11-01-2004, 08:50 AM:

The blower in the Kneisley has sleeve bearings which most people forget to lubricate. We have had few problems with the connections as long as they are tight and proper air flow.

Posted by Mark Gulbrandsen (Member # 72) on 11-01-2004, 07:45 PM:

Just think Richard... he'll call Kneisley for the new parts and be transfered to "That Extension"......... [Big Grin]

Mark @ CLACO

Posted by Richard Fowler (Member # 893) on 11-02-2004, 11:01 AM:

"That extension" is Betty's middle name [Wink]

Posted by Peter Mork (Member # 1336) on 02-18-2005, 11:06 PM:

Sputterin' sprockets! It happened again - another cathode-holder meltdown (even though we recently installed a brand-new lamp fan). You know you have trouble when the picture goes dim with a "hot spot" at the bottom.

I decided to try a new approach to the problem, by fashioning a "crutch" out of a strip of plaster drywall with the paper removed (so it won't burn) and propping up the rear end where the plastic holder attaches. Has held up so far.

If you want to try this, remember whatever you use as a prop should be non-conductive and heat resistant.

You may call this a Mickey Mouse solution, but it floats my boat.

Posted by Michael Schaffer (Member # 1204) on 02-19-2005, 07:18 AM:

Peter - it happens all the time! In the one location where we have those wonderful consoles, we always have a few cathode adapters and cables ready. It is the only remedy.

quote: Peter Mork
You may call this a Mickey Mouse solution, but it floats my boat.

I call it a Mickey Mouse console, so that is an apt solution.

Posted by Gordon McLeod (Member # 33) on 02-19-2005, 07:33 AM:

Out of interest did you check the cable tightness and the tighness of the lamp collet and what was the ceiling exhaust.
I have never had that problem except where those were an issue and at the same location the super lumex's did the same thing also has anyone checkt eh actual current your lamphouses are drawing with an accurate clamp on meter as those lamphouse meters are notoriously inacurate

Also how did you clean up the discoloured cables? The connectors must be polished back to a nice shine as does the mating area as well as the interior of the collet as otherwise the cycle will continue to happen due to contact resistance causeing heating

Posted by Peter Mork (Member # 1336) on 02-19-2005, 08:45 AM:

Yeah, did that stuff. But any cable, etc. that I replace is just going to go bad later on. I doubt I can make a silk purse out of this baby, and I'm tired of trying. I just want to do what I can to keep it running and in alignment, hence the "crutch" method.

Posted by Mark Gulbrandsen (Member # 72) on 02-19-2005, 12:00 PM:

I used to sell gobs of Kneisley stuff back in the midwest area and never had this problem. I had a few burn't up connections now and then, mainly contactor wiring issues but nothing like you guys are experiencing with them. I would reccomend that you make up your own cabling and replace the Kneisley factory stuff with your own or locally swaged made up cables. As for the rear lamp support I can basially say the same thing, very few failures. Only in Super Lum-Ex's after they are 20 years old or in installations with insufficient exhaust air flow. That support is supposed to be made from Teflon bar stock and Teflon is pretty good at resisting heat over a long, long time. Makes me wonder if they are using some other plastic stuff er somthin in place of the teflon... Also, Teflon does not melt it just gets brittle over time!! I'm suspecting some other stuff has been substituted for Teflon in the bulb supports.

A permanent fix would be to gut the lamphouse and install the Christie Plenum kit.

Mark

Posted by Gordon McLeod (Member # 33) on 02-19-2005, 01:09 PM:

All well and good but the fact that the holder is melting and the cable burning is a serious safety issue and not to address its cause and find a cure could be looked at as negligence if there was a fire or workplace injury as a result
crutches are all well and good but operating with a known potential safety issue is a serious issue not to be taken lightly

That said like Mark i installed more Xenex II's than I care to think and have only had a few failures and all due to other issues causing the failure loose connections and bad cooling

Posted by Michael Schaffer (Member # 1204) on 02-19-2005, 07:39 PM:

Speaking of all that, can somebody recommend a good cfm meter?

Posted by Tim Reed (Member # 137) on 02-19-2005, 09:06 PM:

Another thought, in the area that Mark and Gordon mentioned... If there's plenty of airflow in the right places, I'd be willing to bet the holders are slightly large or out of tolerance, enough that they're not making proper contact around the circumference of the bulb pin. You can run the clamp down really hard, and the bulb seems tight, but it isn't really making full contact, if you know what I mean.