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Author
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Topic: Solar Cell, Exciter Bulb, & Audio Out questions
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Gerard S. Cohen
Jedi Master Film Handler
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Posts: 975
From: Forest Hills, NY, USA
Registered: Sep 2001
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posted 01-18-2003 03:14 PM
My pair of Holmes Type 8 Educator 35mm Projectors share an L25N vacuum tube amplifier, although the manual gives a diagram and instructions for the cheaper L25N amplifier as well. Each machine has a PE (Photo-Electric cell,) the cables from which are thick and wrapped with braided wire shielding. When only one projector is used, the connection is capped to keep out moisture and stray interference. The tube amplifiers apparently include a pre-amp circuit, and provision is made for both permanent magnet speakers, or the older dynamic type that uses a current-activated magnetic coil. Tubes for the K15F amplifier are: #80 (1), #56 (2), #57 (1), #2A3 (2). Tubes for the better L25N include the #6J7. I find I usually have to turn up the volume control to the maximum to get adequate sound from a 16 ohm Bell & Howell speaker in its cabinet intended for use with a 16mm B&H 385 projector.
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Bruce McGee
Phenomenal Film Handler
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Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999
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posted 01-19-2003 04:36 AM
Gerard, those are some mighty-fine amplifiers you have there!
My L25N uses 6J7, 6J5, 2-6L6G, 5U4G, and maybe one more 6J5. Right now I am 20 miles away from my amp at work. It produces a good 25 watts of power @ 8 ohms. It's been recapped. Before the recapping, it had a bit of hiss in the audio, but that is gone now.
I converted my Holmes to a solar cell. I have good quality sound when I just use the mic input on a regular PA amplifier. Even a 16mm projector amp does the job, too.
Michael: Sounds like you are dealing with a standard photoelectric cell. It is a unique looking 4-pin "radio tube" looking item inside the small round can. I installed a solar cell out of an Eiki 16mm machine in my Holmes. It works even better than I expected... Next step: Stereo!
You might check the wires between the 4-pin socket and the output jack on the projector. These can vibrate loose. [ 01-19-2003, 07:51 AM: Message edited by: Bruce McGee ]
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Michael Trotochaud
Film Handler
Posts: 11
From: Alexandria, VA, USA
Registered: Dec 2002
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posted 01-19-2003 11:00 AM
I have two machines, one runs and the other is strictly a parts machine. I checked them both, and the running machine has a solar cell and the parts machine has a photoelectric cell. To describe to make sure I'm correct, it is a small piece of plastic with a metal plate on it. There are two wires coming out of it with a mesh shielding. The parts machine is definately running a tube.
The mesh shielding's ground clip was not grounded and I was able to ground it. I now have audio, however it is extremely bassy. Jim, you mentioned getting proper audio equipment. Are there any recommendations as to where I can get some at a constrained budget price? Are there any suggested setups for minimal pricing? I see references to running this through a microphone jack on a PA system. Does this work well? How is the bass on it?
Also in my original post, I asked about increasing/decreasing the wattage of the exciter bulb. What effect will that have? What size bulb should I be using in the first place? Also what is a good power source for it? Right now I'm running this bulb off of a rechargable battery. I'd like to use an AC powersource with a DC convertor, but before I buy one, I want to make sure I'm running the correct voltage.
Mike
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