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Author Topic: Running Smaller Lamps in an SLC-70 with SanRex Rectifier Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 07-04-2014 01:12 AM                     Hello all. I've been a 16mm collector for ages, but a few weeks ago I picked up a complete 35mm system from a local DI. Not a bad setup, with a Century SA projector and TR4 soundhead, Christie SLC-70 console, and Strong platter system (the only not-so-great part, but it works just fine). It suffered a great deal of neglect and poor initial planning though. They ran the air-cooled SA with 6k xenons, never bothered to check/change/add oil to the intermittent, and upgraded the soundhead with a BACP RSTR-2000, but never bothered to align it. Just thrown in, outputting nothing above a few kHz. All things considered, it survived decently apart from a nasty hole in the shutter, but that's an issue for another thread. The original rectifier in the SLC-70 had been replaced (upgraded?) with a SanRex KCX-180H2CR, which from the slim amount of information I was able to find, is the series of rectifier installed in the later Christie SLH-D lamphouse pedestal. Since this projector will be filling something considerably smaller than a drive in screen, that leads me to my main question: How far can the rectifier be "dialed down" to operate a lamp of lesser current rating, and does the lamphouse design of the SLC-70 in any way limit the ability to do so? I was considering a test with the 6k lamp that came with the system to see how far down I could set the supply, but the unit is not yet in a location with 3-phase power (it will be soon). I'm not sure how safe that is anyway, but it would have been a very short-term test. I'd rather not have to provide all the cooling requirements for a 6k lamp for temporary testing purposes anyway, as the final installed system would ideally be something much smaller. Any documentation at all on the SanRex rectifier, including schematics, would be immensely appreciated as well. I can easily provide pictures if need be. Thanks in advance. Reading past forum posts has been of great help already. —Tom  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 07-04-2014 01:21 AM                     The smallest lamp you can put in it is a 4500 watt. Hope you have a pretty big size screen. Even with the jumpers in the low position and the adjustment all the way down, you'll be pushing a bit over 4000 watts into the lamp. If this is for a home theater, your only real option would be to get a 3 bladed shutter for the projector to cut that light in half. Check with Cardinal, as they may have them.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-04-2014 12:18 PM                     Most sanrex rectifiers offered standby mode when the lamp could idle at half power the only issue if run for long periods at the low standby mode with the taps at low (4k) it would be about 2K but the filtering is very dirty and lamps don't last  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 07-04-2014 12:29 PM                     You should be able to get all the way down to a 2k (or even 1k) bulb IF you can get two things done: 1: Get a smaller rectifer to run the bulb (should be really easy and cheap to do actually with all the equipment pulled out lately) AND: 2: Have a machinist fabricate adapters for the bulb you want to use. You will need to get the arc "center" dimensions from the 6k bulb for example, and the adapters will be made to bring the lower wattage bulb's arc center to the same dimension. The adapters should be made of a good grade of brass. I have used the adapter trick with good results on a few different lamphouses.  |  IP: Logged Alastair Bowlie-Evans Film Handler Posts: 34 From: South Wales, Swansea Registered: Jun 2014 posted 07-06-2014 11:41 AM                     I dare say--You could re-work that three-phase rec,--wiring all the three transformer primaries in series, thus dividing the power to 1/3rd... BUT--Huge issue then is, insufficient smoothing. You would have to re-wire the secondaries too and replace the three-phase bridge with a single-phase, And Triple--at least--the capacitance of the smoothing-block... Not for the feint-hearted!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-06-2014 02:32 PM                     I believe that rectifier is a switch mode device and would not like the conversion of input configuration to be in serries  |  IP: Logged Alastair Bowlie-Evans Film Handler Posts: 34 From: South Wales, Swansea Registered: Jun 2014 posted 07-07-2014 10:34 AM                     Ah--I had assumed--It was a Linear rectifier, not a Switch-Mode type.....  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 07-11-2014 12:58 AM                     I don't think it's a switching supply, but I don't have the schematics, and I haven't had the time to inspect it thoroughly. It seems to be a linear supply though, with thyristor based electronic current regulation. I'll try to upload a photo of it soon. The rectifier model is KCX-180H2CR, and I found that the SLH-D pedestal uses the KCX-180CR, which sounds like it's probably the same thing. If so, the lamphouse and pedestal/rectifier specs can be found here. It looks like it's nothing more than a two-piece SLC-70 with a new rectifier. Those specs say it can run down to a minimum of 100A at 31V, which would be 3.1kW. The lamphouse specs say the system will take between a CXL 40 and a CXL 60. Also I was under the impression, from multiple Christie projector specifications (including those above) and data sheets, that the CXL 20 through the CXL 60 were compatible with the same digital projectors. Can I then assume they have the same length and arc centering attributes (apart from perhaps the quartz envelope size)? I read somewhere that the next lamp down from a CXL 20 requires the adaptors to center the arc. Based on this little bit I've found so far, it sounds like running a 4kW CXL 40 in the lamphouse should be possible without modification. If the specs or my logic are in error, which is totally possible, please correct me. If the arc centering is different, could the electric lamp position adjustment controls on the SLC do enough to compensate? And Brad, I'm not familiar with Cardinal, but a 3-blade shutter sounds like an excellent idea. I've always liked the look of their reduced flicker, and my original shutter has a hole burned through it. Do you have contact information or a link for them? Also, would their 3-blade shutters have the same sort of fins the original has for cooling the trap?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-11-2014 09:38 AM                     SanRex did build many thyristor controled powersupplies but the same issues would apply of poor filtering and no load voltage if reconfigured  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 07-11-2014 12:28 PM                     I was thinking it wouldn't have to be reconfigured. Based on those specs, I would think the supply was just designed for a wide range of output, at least for 4k-6k lamps. It will be operating on proper three-phase, so there won't be any input power changes. Assuming the current regulation on the supply has sufficient range, the output circuitry, and thus the filtration capacitors, would remain the same. Is such current range on a supply of this sort unheard of? It definitely appears to be more advanced than the original SLC supply. Here's a photo of the rectifier:  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 07-14-2014 12:25 PM                     quote: Tom Ostertag ....that the CXL 20 through the CXL 60 were compatible with the same digital projectors. Can I then assume they have the same length and arc centering attributes (apart from perhaps the quartz envelope size)? No, that assumption can be very incorrect. The very fact of the bulb's having different overall lengths means that the arc gap center will be different. (Some of the CDXL bulbs have very close physical lengths and arc centers.) The standard cinema bulbs have differing arc centers in most cases. The digital projectors have differing hardware for the sizes of bulbs they will accommodate. See my post above for the answer to the bulb size issue. For example, check out this PDF from Superior Quartz Products lamp specs: Xenon short arc specs to see the differing lengths (Start with 1k bulbs on page 48), look at the dimensions for "Tip to Shoulder Length (L2)" which is the length from the cathode base to the cathode tip. Find that length for a 6k bulb.. as a round number example, say 3 inches. Then find the length for a 2 k bulb, again for a round number example, let's say it's 2 inches. So you will need a 1" adapter on the cathode end of the 2k bulb to get that "Tip to shoulder" dimension equal to that of a 6k bulb. ***The above dimensions were used as an example ONLY, you MUST find the actual dimensions for the 6k bulb and any other you want to use. *** You can, with the bulb in a protective cover, use a ruler or tape measure to get the dimensions from the bulbs, as long as you are accurate to about 1/8th of an inch (easy enough to do by that method) and the lamphouses' focus mechanism will have enough range to work. In many cases you'll need the same length adapter on the anode end to allow it to reach the front bulb support.  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 07-31-2014 08:09 PM                     Wow, thanks for that resource! That's exactly the sort of spec list I've been looking for. Fortunately, the tip to shoulder length between the CXL-60 and CXL-40 equivalents only deviate by .08", and the overall length by only .04". Should be well within the range of adjustability. Now, if I want to go with something smaller than a 4k, I'll definitely need to go the adaptor route, as that's where the dimensions start to change dramatically. The projector is in a space with 3-phase now, so I can begin testing the rectifier. Then I'll be able to see how adjustable that is.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-31-2014 09:53 PM                        Certainly on the old Christie rectifiers you could only lower the current, which, in turn, lowered the "open circuit" voltage. (Not a good thing.) There were extra wires to allow the open circuit voltage to be increased when required. The system was to adjust the current first and then adjust the no load to be proper.  |  IP: Logged

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