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Author Topic: 4KW rectifier with 3KW lamp Giorgio Volpi Film Handler Posts: 51 From: Caracas - Venezuela Registered: Mar 2002 posted 03-31-2006 05:30 AM                     Hi, a new customer of mine has a Strong Highlight consolle with a 100-150A rectifier. He used to use a 4KW lamp, but after theatre change is using a 3KW one. The lamp life is very short. Do you think is for the inappropriate rectifier or for any other reason? Thanks in advance, Giorgio.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 03-31-2006 06:41 AM                        Does that console have a switching (black box) or high reactance power supply? Whatever it is, the current needs to be throttled down to 85-90A for a 3k lamp. Running it at a higher current setting as for 4k will definitely mess it up fairly quickly. The switching power supplies can be quickly and easily adjusted by either one or two trimpots (fine and coarse) which are either located on top or the side of the PS or may also be mounted on the side of the lamphouse, below the current meter. The high reactance PS is adjusted by input tabs on the side. I believe older versions also had a dial switch for this, but I haven't worked with one of these, so someone else has to comment on this. The next important step would be to identify which type and model of PS you have. The current can be read from the meter in the side of the lamphouse. But I wouldn't rely on this. Better check the current with a clampon ampmeter.  |  IP: Logged Giorgio Volpi Film Handler Posts: 51 From: Caracas - Venezuela Registered: Mar 2002 posted 03-31-2006 08:10 AM                     Thanks, Michael. The console has a high reactance power supply. It is at the minimum regulation. When the lamp is on the ammeter shows 110A and when the lamp is hot it shows 100A. Never less than that.  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 03-31-2006 08:57 AM                     Giorgio, since you at the low range of the power supply an option is to control incoming voltage via buck/boost transformers or a variac set. I have done this on locations powered by generators and one situation where the power varied +/- 20% during the day. The limitation would be increased current used.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-31-2006 09:01 AM                        Remember also that the "no load" or boost voltage must be accomodated as well. If you have reduced the current appropriately, you will probably be LOW on no load DC. Usually there is another tape on the low current secondary to get additional "no load" voltage. Louis  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 03-31-2006 04:16 PM                        But would this affect the ignition boost circuit? Like you said, that circuit feeds off the secondary coil of one of the phases. But Richard meant controlling the power coming into the PS. Since that would throttle the voltage by about 10%, the ignition boost should still be sufficient.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-31-2006 08:21 PM                        Many rectifiers (especially Christie) literally won't light at all after a couple hundred hours. The problem is that the voltage that is normal is nearly at the top end of the capacitor break-down voltage rating. When the current is lowered from 140 amps to 105 amps, then the no load voltage falls too far. You are lowering the current with the primary on the large transformer; the "boost" secondary falls too far. Louis  |  IP: Logged Giorgio Volpi Film Handler Posts: 51 From: Caracas - Venezuela Registered: Mar 2002 posted 04-01-2006 12:20 AM                     Thank you very much to all you. Giorgio.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-01-2006 01:42 PM                     Often I have had to add an outboard boost supply circuit to them to light when the rectifier is turned way down Kniesley also has that issue  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 04-02-2006 01:51 PM                     Personally no problems using LPA type of rectifiers....more problems with Christie as Louis stated. Kneisley had a R-2924 boost kit as an accessory. My last order of that kit poor Betty came through since she had to call an independent engineer to verify that they had the parts to make our order  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 04-02-2006 09:46 PM                     quote: Louis Bornwasser Many rectifiers (especially Christie) literally won't light at all after a couple hundred hours. The problem is that the voltage that is normal is nearly at the top end of the capacitor break-down voltage rating. When the current is lowered from 140 amps to 105 amps, then the no load voltage falls too far. Never had a problem like this runnning a Christie 4kw rectifier at 3kw. I must have at least a dozen running this way and they all ignite just fine. Ditto with LP as Richard mentioned. Strong is using LP high reactance supplies in current products so Georgio might have one of those...... Thee clue to it being an LP rectifier are the gold colored heat sinks. Mark  |  IP: Logged

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