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Author Topic: Bulb doesn't want to strike Martin Murray Film Handler Posts: 69 From: ennis tx Registered: Sep 1999 posted 09-28-1999 08:24 PM                     I have a problem with a single phase Xetron P1X80/100 rectifier. Sometimes the bulb will light immediatly, usally you have to keep pressing the manual ignite several times. The problem is not with the bulb {Osram 3000w with less than 400 hrs} or the lamphouse {Xetron XH15 model3000} it is the rectifier. The reason I know this is a couple weeks ago a diode went out in the Xetron rect. so I temporarly replaced it with a 2kw Kniesly and the bulb lit every time. Yesterday my new diodes came in and I replaced all 4, hooked the rectifier back up and it was same as before, hard to strike. After the bulb is lit it seems to be fine. it is running 29.1 volts, 106-108 amps, no load voltage is 68.1. also if it makes any difference it seems that the capacitors hold a charge less than 30 seconds after the rectifier is turned off. Also when the bulb first lights the amperage starts at 80-90 increases to about 110-115 amps then drops back to 106-108 where it stays after the bulb warms up. This rectifier is in a drive-in that does not have 3 phase power accessible and single phase 3kw rectifiers seem to be hard to come by so I really need to get this one fixed. thanks Martin  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 09-28-1999 09:30 PM                     Sorry I don't have a schematic for this rectifier (I beleive Gord McLeod does, however). My first guess would have been that the electrolytic capacitors in either the filter or boost circuit are starting to dry out - except that the lamp sometimes strikes immediately. This could be verified by temporarily paralleling them with another capacitor about the same rating. Is it possible that the nichrome wire on the bulb is causing the striking current to jump to the reflector housing? You may be able to see this through the arc-sight glass or through the adjustment holes in the lamp.  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 09-28-1999 10:13 PM                     O.K. here's my second guess. It may be possible that the small ceramic bypass capacitors that bypass the high ignition voltage from going into the rectifier may have failed (opened, blew-up, whatever). This might be the reason for the recent diode failure (the ignition voltage exceeded the P.I.V. of the rectifier diodes - the first one that shorted saved the other diodes from blowing). This would also make for difficult striking. To prevent this from happening on other rectifier installations, I usually bypass the D.C. from the rectifier with a small ceramic capacitor. My favourite animal for this is a Centralab DD-104 (0.1 uF @ 1000 volts). Just put one of these across the D.C. terminals at the rectifier. It won't affect the D.C. at all, but will keep the high-frequency ignition voltage from getting at your diodes, and provide better ignition as well.  |  IP: Logged Ken Layton Phenomenal Film Handler Posts: 1452 From: Olympia, Wash. USA Registered: Sep 1999 posted 09-29-1999 12:21 AM                     If your rectifier has that RA relay board in it, I have seen some of them go bad. Sometimes the relay contacts would get pitted and get stuck and if I remeber right , there was a small axial lead electrolytic capacitor also mounted on that board that would go bad.  |  IP: Logged Martin Murray Film Handler Posts: 69 From: ennis tx Registered: Sep 1999 posted 09-29-1999 02:59 AM                     Thanks Rick, I did forget to mention that this rectifier was in storage for 12 yrs while the drive-in was closed. If I can find 5 4200 uf caps today i will change them as well as adding the small ceramic cap. The last owner of the drive-in always had diode trouble as well so I did step up from the 45 amp diodes to 85 amp, they were the biggest I could find that would fit the bridge. I'll let you know what happens. Martin  |  IP: Logged Aaron Mehocic Jedi Master Film Handler Posts: 804 From: New Castle, PA, USA Registered: Jun 99 posted 09-29-1999 07:52 AM                     Martin, I had problems like this many years ago with the power supply in an old Christie console. The booth techs told me to make sure there was an air flow over the diodes so as they don't overheat and fail. If the other guy who had this rectifier had trouble, and it was in storage for 12 years, make sure there is some type of air circulation within the machinery. For what its worth, Aaron  |  IP: Logged Art Averett Film Handler Posts: 14 From: Orlando, FL Registered: Mar 2000 posted 09-29-1999 10:00 AM                     The one place you might want to check is the boost voltage. It should be in the order of 120 to 150 volts dc, no load. From what you described , the boost voltage is low. Check the boost voltage diodes and caps. Also check the bleeder resistor. If there is, check its resistance. Also check to see if there is a relay that puts that resistor across the caps after you shut down the power supply. It might be that the relay is putting the resistor across the caps all the time, where as it should only be at shut down. In changing the diodes make sure that they have a higher Peak Inverse Voltage (PIV) rating than the last ones. Just for the heck of it, check the contactor, if it has one. Sometimes the contacts get corroded and will drop the AC voltage down. Hope this helps you, Art.  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 09-29-1999 05:03 PM                     BTW did you remember to apply heat sink compound when you installed the new diode? If not, it's available at most electronic parts outlets.  |  IP: Logged Martin Murray Film Handler Posts: 69 From: ennis tx Registered: Sep 1999 posted 09-30-1999 05:38 AM                     Now I Know more, I have got the bulb where it will light every time. I discovered that the bulb would not light until the no load voltage reached 65, so I readjusted the auto-ignite so it will not attempt to strike until nlv is 66 volts it works every time now, however it takes at least 45 seconds sometimes longer to reach 88 mph oops I mean 66 volts. Does this mean the caps are bad or could it be one of the resistors on the back of the bridge? Here is what else I observed To Ken, there is no RA board in this rectifier. The only relay in it is the contactor. To Aaron, airflow is good, the bridge is not even getting warm. To Art, where is the bleeder resistor? also I installed a new contactor. To Rick, yes I always use heat sink compound. Also the highest I have seen the no load voltage is 68 volts, how can I get it up where it belongs and get it to come up faster? Any and all help is appreciated, thanks ya'll!!! Martin  |  IP: Logged Art Averett Film Handler Posts: 14 From: Orlando, FL Registered: Mar 2000 posted 09-30-1999 07:59 AM                     Martin, check the resistor's around the bridge pack. You'll have to disconnect them. If you can get to them, cut or remove one end of them to take a resistance reading with a good volt/ohm meter, Simpson 260, or a digital meter, Fluke,. If you can see what the color code is, reply back to me and I'll tell you what the value is. If it is a big resistor, you should be able to read what is printed on it. Sounds like the resistor/resistors have changed value. The bleeder resistor is usually across the electrolytic caps. They drain the DC voltage down after you shut off the power supply. Art.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-30-1999 01:15 PM                     The Irem rectifiers like the sanerex always had low no load voltage usually around 85 volts Most likely one of the caps isn't chargeing or the connection to it is bad In that rectifier use 400volt PIV diodes or you will have problems The xetron Ignitor is an IREm and they are extremely noisy so usual bypass caps arn't enough Make sure the capacitor in the filter are at least 100volt In some of the single phase Irems they used a short ceramic fuse in the boost supply check for that  |  IP: Logged Rick Long Jr Expert Film Handler Posts: 211 From: Toronto, Canada Registered: Jul 2000 posted 07-25-2000 06:41 PM                     I have experienced similar problems with O.R.C. and Strong rectifiers. Both types use a Blocking diode which I believe blocks the boost caps from draining across the other ones. In both cases with these units, if this diode is shorted, the no-load voltage takes quite a while to build up (as the other caps charge up) but the unit will eventually light. This diode is usually attached to the positive output of the bridge and conducts the entire lamp current, and therefore is usually larger than the ones used in the bridge (except in the Strong 61000 series). I'm not sure if your rectifier has such a critter, or where exactly it would be, but if it does, this could be the culprit. Hope this helps! RLJ  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 07-25-2000 07:07 PM                     Hmmmmm. And normally the people here on the forum are so quick to respond with solutions.  |  IP: Logged Stefan Scholz Expert Film Handler Posts: 223 From: Schoenberg, Germany Registered: Sep 1999 posted 07-29-2000 01:22 PM                        I think, for a 3kW bulb the no load voltage should be higher than your mentioned 68 Volts. Preferrably over 90 Volts. And remember, do not have extinguishing caps on the output. Arcs do not like capacitors. But normally the inductance of the suplly leads will do. For single phase friends: I have found someone at Cinema Expo Amsterdam selling very compact 1 phase switch mode supplys. The Box is 4.5" wide, 7" tall, 8" deep. It weighs 8.5 lbs, uses 195 to 270 Volts of AC (40 - 60 Hz), with 0.95 power factor primarily, and delivers 3kW continuously, with 4 kW at 45 min interval (140 Amps). The price stated for the final customer was $ 750. He claimes, it workes. I doubt it, it's 100 kHz switch mode technology of the latest generation. Contact: Veronese Paolo, Via Montefior 12 / Milan, Italy.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-29-2000 03:29 PM                     That sound like the IREM switcher. Most of the Irem single phase rectifiers have very low noload voltage just like some of the Sanerex I was working on a Sanrex this week and its no load was 65volts Some of the Ushio HTP lamps are rated for this lower voltage  |  IP: Logged

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