This is topic Want to make a 16mm sound changeover box, what is needed? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Joe Beres (Member # 678) on 04-27-2002, 02:29 PM:
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.
Posted by Paul G. Thompson (Member # 655) on 04-27-2002, 09:45 PM:
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.. 
Posted by Gordon McLeod (Member # 33) on 04-28-2002, 09:08 AM:
Elmo sells a changeover box for pix and soun for these I believe
Posted by Bruce Hansen (Member # 281) on 04-28-2002, 11:52 AM:
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.
Posted by Steve Guttag (Member # 268) on 04-28-2002, 12:36 PM:
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!"
Posted by Joe Beres (Member # 678) on 04-29-2002, 11:23 AM:
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?
Posted by Steve Guttag (Member # 268) on 04-30-2002, 08:28 AM:
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!"
Posted by Tom Sauter (Member # 616) on 05-07-2002, 03:04 PM:
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.