Film-Tech Forum ARCHIVE: Audio problem with Elmo 16 CL

This is topic Audio problem with Elmo 16 CL in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Lisa Kruczek (Member # 10094) on 07-07-2017, 10:25 AM:

Hello everyone-

I'm having an audio issue with my Elmo 16 CL. It's sort of a tinny dragging noise that's happening even when film is not running through the projector. I cleaned the solar battery and sound lens as the manual suggests, but no luck. The rollers are all in good shape as well as we had it serviced last year. Any ideas? I can post an audio file if someone could tell me how to post it here!

Thanks!
Lisa

Posted by Rick Raskin (Member # 1561) on 07-07-2017, 03:29 PM:

Assuming the machine is not running it could be a bad connection or faulty capacitor, etc. etc. Its kind of hard to tell from your description.

Try posting your question on 16mmfilmtalk.com. There are lots of Elmo fans hanging out there.

Posted by Lisa Kruczek (Member # 10094) on 07-19-2017, 08:18 AM:

Thanks Rick, I'll give that a try. And yes, the machine is on but not running film and it still makes the noise.

Posted by Leo Enticknap (Member # 534) on 07-19-2017, 02:29 PM:

I'm not familiar with this specific model, but agreed with Rick - sounds like (excuse the pun!) a bad capacitor or transistor in the preamp stage.

Is there a separate line level and amplified (extension speaker jack) output? There was an arrangement on some either Elmo or Eiki projectors, whereby if you inserted a stereo 1/4" plug into the single jack it gave you line level, but a mono one gave you speaker level. Can't remember any more than that.

If you haven't tried anything other than the projector's internal speaker, hook up a 1/4" to RCA cable, with the other end into a hifi amplifier, PC audio card input, or whatever. Starting with the volume on the projector right down, raise it SLOWLY AND GENTLY to see if you can hear the interference at the other end. If you can, it's a problem in the amplifier module (or, just possibly, the A-chain). If you can't, the internal speaker is bad.

If it is the amplifier module or A-chain, you need an electronics geek who is comfortable troubleshooting printed circuit boards. If you hear irregular cracking while you adjust the volume control, which ceases to vary when you stop adjusting, the potentiometer in the volume control is bad.

Posted by Lindsay Morris (Member # 1430) on 07-19-2017, 07:48 PM:

The 16CL amp is VERY simple in that it uses only 3 IC chips & it is rare that they fail. (Only failure I have ever had was the output chip where the owner was using an extension speaker that was short circuit & killed the OP chip.)

If your machine has a mic jack (some do & some don't) try inserting a bare 3.5mm mic plug into the mike jack which cuts off the feed from the solar cell & then wind the volume up & listen to see if the noise stops.
If no mic jack then you can get at the solar cell leads (just under the lamp cover) which are covered by a small plastic cover. Remove that and short the solar cell leads & wind the volume up & check if noise comes and goes as you apply & remove the short. A small screw driver will neatly bridge those 2 terminals.
IF the noise is there with a short applied then your amp itself is faulty & needs looking at.
Richard Patchett on the 8MM Forum has a range of Elmo spares & might be able to assist or may know someone who would tackle the amp which is really easy to get out.
If you get the back cover off there are a couple of small plugs on the amp board that connect it to the machine & its not uncommon that the pins have gotten a wee bit grotty. Often simply unplugging & reinserting each a couple of times fixes odd noises. One very common problem is that the exciter supply is also on one of those plugs and suddenly the exciter goes out but its not a blown lamp. Its only the pesky plug connector gone open circuit & as soon as you remove & replace that particular plug the problem ceases.
So I would check those plugs as well.

Posted by Lisa Kruczek (Member # 10094) on 07-20-2017, 08:30 AM:

Sounds like I've got some real work to do. Just in case this helps to narrow down the problem, here's the sound

https://soundcloud.com/user-492979374/projector-audio

Posted by Lindsay Morris (Member # 1430) on 07-20-2017, 08:42 PM:

Lisa,

I listened to that sound clip & IF you are recording that with the Volume control on the Elmo up full then what you are hearing is the perfectly usual power supply hum normal on almost all Elmo's I have ever tangled with.
Normally with film running the hum is inaudible & nothing really to worry about.
However that tink tink noise only just audible sounds like microphonics within the amp as the mains power transformer ever so slightly moves the projector body.
Some IC chips are microphonic & many will say that with solid state stuff it aint possible but I have encountered a few in the past with the most recent one being an encapsulated solid state preamp.
I attempted to mount it on a 16mm machine as part of a conversion from photo cell sound to solar cell sound.
After taking out the old valve preamp bits I had heaps of room to mount this European made black plastic block in there & hook it all up. Result was horrible microphonics that was most annoying during quiet passages of film soundtrack. Mounting the thing on rubber mounts improved the sound but I ended up opting for a kit type preamp mounted externally away from the vibration caused by the intermittent movement of this 16mm machine.
Even when out on the bench all powered up and feeding into a power amp tapping the plastic block with a pencil produced a huge signal from a solid state device. [Eek!]

If you can run the 16Cl & reproduce quite intelligible sound from it & the noise you hear is barely audible you do not have a problem. [Smile]