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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Want to make a 16mm sound changeover box, what is needed?

   
Author Topic: Want to make a 16mm sound changeover box, what is needed?
Joe Beres
Jedi Master Film Handler

Posts: 606
From: Minneapolis, MN, USA
Registered: Nov 2000


 - posted 04-27-2002 02:29 PM      Profile for Joe Beres   Email Joe Beres   Send New Private Message       Edit/Delete Post 
I want to make a switch box that will allow me to switch between sound sources from two portable 16mm (Elmo cx-350) projectors. I am not all that knowledgeable in the realm of electronics, but I assume this could be a simple procedure involving a few components. Can anyone give me some guidance? The more specific, the better.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000


 - posted 04-27-2002 09:45 PM      Profile for Paul G. Thompson   Email Paul G. Thompson   Send New Private Message       Edit/Delete Post 
First, do those machines have that option? If not, do it like they did in the 1920's....a hunk of sheet metal that goes "Clunk"!!!

Or something you can control with a Johnson bar..


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Gordon McLeod
Film God

Posts: 9470
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 04-28-2002 09:08 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Elmo sells a changeover box for pix and soun for these I believe

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Bruce Hansen
Jedi Master Film Handler

Posts: 847
From: Stone Mountain, GA, USA
Registered: Dec 1999


 - posted 04-28-2002 11:52 AM      Profile for Bruce Hansen   Email Bruce Hansen   Send New Private Message       Edit/Delete Post 
Are you talkiing about just switching the speaker outputs? If so, a DPDT switch is all you need. You may need to put a 470 ohm (or about that anyway) accross each projectors speaker output, inorder to keep the output coupling cap. charged, otherwise there might be a "pop" sound when you switch. BE CAREFUL, shorting any wires together, even just one strand, can cause the destruction of the projector amps.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12299
From: Annapolis, MD
Registered: Dec 1999


 - posted 04-28-2002 12:36 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
As Gordon pointed out, the CX-350 has available a factory changeover box (picture and sound). Incorporated in the changeover box are large loading resistors for the sound.

The douser and motor functions appear on the DIN connector on the rear of the unit. Thus, you can make your own picture changeover rather easily with a switch. The Elmo box is rather weird in that it presumes you want a 3-second changeover....thread up 3 seconds prior to where the first picture starts...when you hit the incoming projector start button...3 seconds later..whola.

Steve

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"Old projectionists never die, they just changeover!"

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Joe Beres
Jedi Master Film Handler

Posts: 606
From: Minneapolis, MN, USA
Registered: Nov 2000


 - posted 04-29-2002 11:23 AM      Profile for Joe Beres   Email Joe Beres   Send New Private Message       Edit/Delete Post 
Basically I am trying to have a smoother changeover for very little money. These projectors do not get used that often, as they are not in our main auditorium, so i can't justify any great expense. In my previous job, we had a pair of Eiki ex-3500 that had the line out from each projector wired into a switch box with a single output. It made for a pretty decent changeover once you got your timing down. It seems like that would be a pretty easy and cheap solution. Can it be done with the Elmos?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12299
From: Annapolis, MD
Registered: Dec 1999


 - posted 04-30-2002 08:28 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Joe,

Yes you can make a switch box like that for the ELMOs.

The Aux out jack on the back-left side is at line-level 600 Ohms (mini-phone). It will disconnect the amplifier section but leave the internal speaker to load the amplifier. The volume knob will still work as normal.

Thus, you will need to have your switch to select which "Aux Out" jack to play. The picture part will come from the DIN remote connector. I don't have the pin out in front of me but there is one for the douser so you can (with enough poles on the switch) have that also on the same switch. Thus have a single switch changeover. You will still need to start and stop the motors manually like the big boys do but other than that, you might be out $50 or less in parts.

Steve

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"Old projectionists never die, they just changeover!"

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Tom Sauter
Expert Film Handler

Posts: 163
From: Buffalo, NY, USA
Registered: Sep 2000


 - posted 05-07-2002 03:04 PM      Profile for Tom Sauter   Author's Homepage   Email Tom Sauter   Send New Private Message       Edit/Delete Post 
Joe,

The pinouts on the remote connector are as follows:

Jump pin 1 to pin 8 (this sets remote control mode)

Put switches in between the following:

2 and 3 = Lamp On/Off
5 and 3 = Forward/Stop
7 and 5 = Douser Open/Closed

To run in remote mode plug in your cable and turn the projector knob to "forward". It will just sit there doin' nothing until you close the circuits.The grounds in this setup are designed so that you MUST run the motor to open the douser.

The female connector pins are as follows, looking from the front:

TOP
7 6
3 8 1
5 4
2

I know the formatting is weird, but you get the idea.


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