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Author Topic: Solar Cell, Exciter Bulb, & Audio Out questions Michael Trotochaud Film Handler Posts: 11 From: Alexandria, VA, USA Registered: Dec 2002 posted 01-18-2003 09:08 AM                     I own a Holmes 8 projector and have yet to successfully get audio out of it. I am running what I believe to be a solar cell pickup with a 10 volt/5 amp exciter bulb. These are my basic questions. If I increase the volt/amp of the exciter bulb, will that increase the quality/level of the sound? Does the solar cell need to be grounded? What is the output level of the solar cell? In other words, how much do I need to boost the signal to obtain speaker audio? I have tried running it into a 25w amp, and with the volume turned all the way up, I get very little sound and a whole lot of hum. Does the signal need to filtered at all, like a turntable, or is it line quality? Any and all advice that you can give me will be greatly appreciated. I'm tired of watching silent movies knowing full well that there is audio. Mike  |  IP: Logged Jim Alexander Film Handler Posts: 71 From: Greenwood, Nova Scotia, Canada Registered: Nov 1999 posted 01-18-2003 11:11 AM                        To start with, the soloar cell out put is extremely low level. Even lower the a turntable. As such, you will need a pre amp to bring it up to line level. Also, since it is such a low level, any noise from improper grounding or interferance will get amplified with it and "drowned" out the audio. I have built up a sound system off a solar cell using off the shelf components in the past, and the noise aspect is the hardest to overcome. Make sure all the low level signals are shielded and grounded to a good ground at one end only. The cell itself does is not grounded, it uses a floating ground. To save yourself alot of problems, you might want to look into getting the proper amplifier/processor for your configuration. Doing it this way involves alot of calculation and filters. It may be more work than you expect and it might not give you what you expect.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-18-2003 01:57 PM                     1st verify thst it is a solarcell not an older PE cell The PE are in a glass tube the Solarcells are usually a plastic block If it is a PE tyhen you need to provide a DC bias to it and then a decouopling transformer If it is a solar cell then its output should feed a preamp with a maximum of 600 ohm impedance and a gain of about 30 db to start with For mono most mic mixers will do  |  IP: Logged Gerard S. Cohen Jedi Master Film Handler Posts: 975 From: Forest Hills, NY, USA Registered: Sep 2001 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.  |  IP: Logged Bruce McGee Phenomenal Film Handler Posts: 1776 From: Asheville, NC USA... Nowhere in Particular. Registered: Aug 1999 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 ]  |  IP: Logged Michael Trotochaud Film Handler Posts: 11 From: Alexandria, VA, USA Registered: Dec 2002 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  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-19-2003 11:08 AM                     On the 35mm forum some one has a Smart Mod3 for sale that would do the job  |  IP: Logged Bruce McGee Phenomenal Film Handler Posts: 1776 From: Asheville, NC USA... Nowhere in Particular. Registered: Aug 1999 posted 01-19-2003 12:41 PM                     I run my cell through a 12-band equalizer that I got for $5 on eBay. The output of the EQ is hooked to my pre-amp, and is run flat thru it to my Dynaco power amp. Decent sound for me. Glad you got sound. Bruce  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 01-19-2003 01:10 PM                        The fact that you say it's "really bassy" leads me to suspect that you have the cell output plugged into the magnetic phono input of your amp. Turntables use a RIAA equalization curve, which adds a lot of bass. A microphone input has a flat responce curve and will work much better.  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 12-30-2010 02:52 AM                 It has been 2901 days since the last post.  |  IP: Logged Jim Henk Master Film Handler Posts: 364 From: San Diego, CA Registered: Feb 2006 posted 12-30-2010 02:52 AM                     Bruce McGee said: "I installed a solar cell out of an Eiki 16mm machine in my Holmes. It works even better than I expected... " I'm having trouble visualizing a solar cell with a small surface area meant for picking up a 16mm soundtrack working great for a 35mm soundtrack with a bigger surface area to be tracked. Why would this work so well? Thanks.  |  IP: Logged

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