This is topic Another Super Lumex ignition problem... in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Barry Hans (Member # 477) on 05-23-2002, 12:36 AM:
I have two Super Lumex lamphouses with switching supplies running 2000 watt bulbs. Two or three times a week you turn on the lamp and the current raises to about 25 amps and stops. Turn the lamp off/ turn it back on and everything is fine. This happens on both lamphouses. The lamphouses were bought and installed about a year apart. One lamp has a Christie bulb the other a Osram. Power is coming from the same breaker panel but different circuts. It seems that it has to be an incoming power issue but voltages seem good. Both are running off of single phase. I am stumped on this one guys. Anyone have any ideas?
Posted by Paul G. Thompson (Member # 655) on 05-23-2002, 01:08 AM:
Barry, are the Xenon lamps at full brightness when this happens? If they are, thump the ammeters with your fingers to make sure the ammeters are not sticking. You might want to check the meter connections to the meter shunt. I had one go goofy on me some time ago, and the wire was fried at the meter shunt connection. It gave me almost the same indications you described.
Is this problem common with both lamps at the same time? If so, more than likely there is a power panel malfunction.
Since they are fed off the same power panel, I would recommend inspection of the power panel mains to insure they are tight with no evidence of over-heating. If everything else seems to come up properly, check the bus bars under the circuit breakers for evidence of over-heating, as well as the circuit breakers themselves.
Malfunctions like this are not uncommon with Square-D snap-in breaker panels. I don't know what you have, but it might have some merit. I have seen a circuit breaker that was arcing off internally which drove a Christie Autowind stark raving sterile-assed nuts! I am sure it could drive a switcher nuts, too. 
Posted by Dave Macaulay (Member # 813) on 05-23-2002, 08:33 AM:
Paul is right, the SLX meters are prone to showing low readings. I've found the problem is almost always due to the amp/volt switch. This is a relatively high current switch (120VAC 5A) being used to switch 50mVDC max and negligible current. "Exercising" the switch (pressing it a few dozen times) should get it working fine for a while. The internal contacts get dirty, with normal use on AC power circuits they are kept clean by the slight arcing when switching... but 50mV and a few microamps won't do that.
That said, I've had at least one Strong switcher do what you describe. I found the system to be working fine when I checked it, they had left the lamp on all day because they couldn't be sure it would start OK but once at full power it would stay that way. I checked it cold the next day and saw what you describe. Replacing the rectifier solved that.
I did check for the obvious problem, a loose connection in the DC circuit. Any such problem will cause local heating at the offending connection with metal discolouration or burnt insulation. A bad lamp connection will usually cause the lamp end to look burnt or discoloured.
With the new switcher models with the plug-in current control you should check that connector, unless it's screwed down securely it can come undone. I've found that unplugging it causes an inability to strike because the open circuit voltage is too low for the igniter, but if it did strike it would run at very low current, as I recall pulling it out with the lamp on gives 25-40 amps on a 1-3K model.I don't want to slag the switching rectifiers, they work quite well and fail quite rarely if maintained (keep them clean!). They are, however, completely impossible to fix locally. A high-reactance unit has simple circuitry and few parts - they can almost always be fixed immediately if one has a contactor, diodes, and some wire. Just opening a switcher to see what's inside is a hell of a job!
Any complex with a lot of switchers should have a spare on hand in my opinion. Strong has an excellent exchange and repair operation but losing a day or two waiting for a replacement would likely cost as much as a spare.
Posted by Steve Guttag (Member # 268) on 05-24-2002, 05:51 AM:
If your rectfiers are the compact switchers....then another source of the problem is them. A "feature" of that unit is that sometimes it will start at low current (25 amps like you say) and about 20 seconds later...it will come up to full current. Did you give it some time to come up (again it may be 20 seconds or longer).This presumes that the lamp was indeed running low (dark).
Steve
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"Old projectionists never die, they just changeover!"
Posted by Paul G. Thompson (Member # 655) on 05-24-2002, 02:24 PM:
Steve, I find that interesting. I didn't think a 2000 watt xenon bulb (especially an older one) could even sustain itself with 25 amps. 
Posted by Tony Ratcliff (Member # 1196) on 05-24-2002, 04:24 PM:
I had a similar situation happen in my place not too long ago.
I had a breaker that was shorting out in the panel. I'd turn on the lamp and only get 20-25 amps. I'd turn if off, wait and turn it back on and all was fine.
I thought I had a diode going out, but they everything on the projector and rectifier checked out fine.
Finally, when the breaker burned out enough to start giving off that scary old "burning wires" smell, we found the real problem. The breaker had a crack and was shorting, causing the lead into the panel to burn up.This also highlighted for us how poorly the panel had been wired, so I had it ripped out and a whole new one put in.
Tony
Ohio Theatre
Posted by Mark Gulbrandsen (Member # 72) on 05-26-2002, 10:51 AM:
Of course if the manufacturers continue using 5 cent meter movements in the equipment you can't expect too much. I always use my DC amprobe to confirm what the meter is telling me at normal service intervals. I can't begin to count how many meters and meter switches I've replaced in the last 20 years.
Mark @ GTS
Posted by Steve Guttag (Member # 268) on 05-26-2002, 01:15 PM:
Paul,The compact switcher will put out that low current stuff (with higher voltage to boot). I had a customer (running 2.5KW lamps) where more than one of those compact switchers exhibited the "feature." Strong gave some silly reason about how it sense power or something and that it could sustain the low current arc. Perhaps Pat could enlighten us.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Barry Hans (Member # 477) on 05-26-2002, 06:50 PM:
OK, the lamps are doing exactly what Steve G. said. Turn them on and intermittently they hover around 25 amps. Instead of shutting the lamps off at that point we sat and watched them flicker for 5 seconds or so and up they went to 75 amps ( or so ). Now what is less harmfull to the bulb, shutting them off and back on or letting them flicker to full current? Neither one can be good. Thanks for the help all!