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Author Topic: Exciter Lamp Wiring Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 07-17-2000 08:56 AM                        Does anyone have a wiring diagram for exciter lamp changeover? What do you suggest for a sound changeover of two projectors: From the solar cell or from the exciter lamp? Which is better? I've heard it's better to keep the lamp on all the time and change over the solar cell. Bernie ------------------  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 07-17-2000 10:56 AM                     There should be a few examples in the manual download page. Exciter lamp c/o's sound bad because there a short delay while the lamp comes up to brightness. Let the processor do it(or switch solar cells.) Some people hook up the lamps such that the current to the lamp is reduced on the non-running projector. Not for sound reasons, just to save the lamps. Reducing rather than shutting off the lamp makes it last longer. You need some power resistors and a few relays with good contacts (exciter lamps are lower voltage but high current.) I can draw a schematic for you if that's something you might be interested in.  |  IP: Logged David Johnson Film Handler Posts: 54 From: Melbourne Vict Australia Registered: Oct 1999 posted 07-18-2000 02:17 AM                     The processor should have this provision, if not switch the output from the preamps, much better than the cell, exciter C/O works ok but you should use a pre heat to stop the gap in the sound while the lamp comes up to full brightness, with the low current, thin filament lamps you should get away with just switching but with American high current low voltage you will need pre heating. David  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 07-18-2000 07:25 AM                        Agreed to all--avoid using the exciter lamp as the sound changeover. It sounds bad when the film drops to silence for a fraction of a second at the c/o and increases the chance that a bulb will burn out right at the c/o. Also, how would you match the levels of the solar cells without feeding them into separate preamps with separate gain controls?  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 07-18-2000 08:02 PM                     Anyone ever try just switching the solar cells? As the switch transfers, the input circuit momentarily goes open, creating a loud "thump" in the sound. Simplex, in one of their designs, got around this by switching a negative d.c. bias to the "off" pre-amp. A capacitor rounded off the edges of the waveform to eliminate the "thump".  |  IP: Logged David Johnson Film Handler Posts: 54 From: Melbourne Vict Australia Registered: Oct 1999 posted 08-01-2000 02:00 AM                     I seem to recall the old Kalee BAF valve sound system which used 6J7s switched the cell directly, I don't recall them being noisy but is bad practice to switch something with this amount of gain following. David  |  IP: Logged

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