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Author Topic: Exciter voltage DC vs AC ...help? Paul Vollmers Expert Film Handler Posts: 161 From: Sister Lakes, MI, USA Registered: Jul 2001 posted 05-09-2004 06:34 AM                     Hey guys...........thanks for your input.............I'm currently using 6 volts AC, as a temporarily power supply, as my 9 volt DC Kelmar is not setup yet. The sound does not seem where it should be..............so your info has confirmed my thoughts. This is a home setup, not corporate theater. Also, this sound issue is on my Simplex SH1000, not the Norelco as pictured. Again many thanks, Paul  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 05-09-2004 02:58 PM                       Oh, do go on! The seminars were always great fun. Was Lonny with me then, or was it George Douglas and Bob Warren? Lonny and I did a seminar for Regal in Seattle two weeks ago. We are polishing our act for the road.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-09-2004 03:50 PM                     Yea, those seminars wre lots of fun and also learning some interesting things. The last one I attended was in 1985 and it was when it was Sam and George Douglas. Its even amazing how many people I met at the seminar that I still keep in touch with today. The trip we all made over to Saul Zaentz Film Center was wonderful! Mark  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 05-09-2004 05:13 PM                        Thanks for the clarification, John. Not all of us are photochemical engineers after all. Josh  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 05-09-2004 05:44 PM                  quote: John Pytlak ...allow complete conversion to prints with cyan dye analog soundtracks, to take advantage of the environmental benefits... John, just out of curiosity, what are the economical benefits to the distributor and/or film lab by having only cyan tracks? (Perhaps this question is more suited for the Cyan Thread... copying over there for reponses.) >>> Phil  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 05-09-2004 10:08 PM                        The major reason has always been the environmental advantages of greatly reduced water usage, less chemical waste being sewered, elimination of a concentrated caustic developer containing hydroquinone, and eliminating almost all silver from color prints that may be incinerated or landfilled. Any savings due to reduced water and chemical usage, and reduced waste, may ultimately reduce the cost of prints. As Dominic Case wrote, contracts between labs and distributor are renegotiated periodically. There is NO CHANGE in the print film raw stock. Film stock manufacturers may actually sell LESS film, since there is less lab waste.  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 05-11-2004 10:21 PM                        This all gets away from Paul's original question, that of AC hum. As Steve mentioned, there was a higher amperage bulb, sometimes with a different voltage rating. The heavier filament did not respond as quickly to the rise and fall of a 60 cycle waveform, so you were (are) less likely to hear hum when using AC power. The 4 amp bulbs will pass some hum into your system, though. I assume you only hear the hum when the exciter is on and you have no film in the machine. With a good ear, you can also hear the hum come and go with dialog, since little light gets through to the cell during silent periods. That can be very distracting. If you put a business card between the light and your pickup cell (in an unthreaded soundhead), the hum should also disappear. If it doesn't, you have problems elsewhere in your system... likely between the cell and your amplifier.  |  IP: Logged Paul Vollmers Expert Film Handler Posts: 161 From: Sister Lakes, MI, USA Registered: Jul 2001 posted 05-12-2004 06:31 AM                     Jack, Thanks for your reply, yes, I do get hum on AC and the hum does go away when a card is placed between the light and the film, so everything is working as it should. My question was to the voltage supplied to the exciter........instead of the normal 9 volts DC, what effect would 6 volts AC be with the sound quality ? other than hum . Paul  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-12-2004 09:31 AM                     It depends on the lamp if you operate an excitor below 80% of its rating then the wo filament supor rods act like heat sinks and lower the filament temp at the ends of the filament produing very poor edge illumination and one ends up with a compressor to the audio  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 05-12-2004 01:20 PM                        Yah... I don't think I'd drop it quite that low. A volt or so can extend the life of your lamp quite a bit, but there are some trade-offs for going too low... which are listed above. In any case, you won't hurt anything the way it is now. You appear to have the right kind of power supply on the way, and that will address the concerns you've raised here.  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 05-12-2004 05:23 PM                     You could also get a bridge rectifer and a filter cap or two, and you should be able to get about 8 volts of DC. The rectifer must be able to handle the current your lamp drawes (always add a little fudge factor), and you may need to heat sink it. Feed the 6 volt AC output of your xformer (hopefully your xformer can supply enough current for your lamp) to the "~" (AC) input of the bridge. Put the caps accross the "+" and "-" outputs of the bridge (make sure that the "+" of the cap is connected to the "+" of the bridge. Then connect the lamp to the "+" and "-" of the bridge (and cap(S)). The caps must be rated to handle the voltage. Somewhere around 5000 Mfd should do for the caps. Make sure that the bridge does not get too hot. You can possibly heat sink it to the projector caseing.  |  IP: Logged

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