Film-Tech Forum ARCHIVE: Analogue Sound Problem

This is topic Analogue Sound Problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ian Bailey (Member # 1752) on 01-28-2008, 01:03 AM:

This is the same machine that has the Ghosting(or Flaring) problem I'm trying to resolve.
There is a hum in the analogue system that can be easily heard in the monitor speaker....not so easily heard in the auditorium.....my hearing is also pretty bad.
But what I can hear in the auditorium when running an analogue show...which has normal dialogue and no extra sounds in the background ......is the Hum increases when there is dialogue and is a lot less in a quiet patch of the show.
JUNO was the one I noticed this on.
It's not the print as we've ran this print in another house.
The equipment is:
Component Engineering Red Led/Reader
Component Engineering Power Supply(only recently installed)
CSP1200
Crap Twin amps
Crap Monitor
The general hum in the monitor can be stopped by pulling either or both of the inputs(will check this again)to the top twin amp which drives the Left & Centre speaker.
I ran out of time to check any further.....and I wanted to get you guys opinions on this one before I have another look.
At the moment all our shows are DTS in this house so there is no rush.
Cheers Ian

Posted by Michael Schaffer (Member # 1204) on 01-28-2008, 02:19 AM:

What happened to your funny hat?

Posted by Monte L Fullmer (Member # 2797) on 01-28-2008, 02:39 AM:

pull the CE reader out and chek the attached leads going into that phoenix (green) plug and see if any of the cel leads have came loose and retighten the screw taps down...for machine vibration loves to work them screws loose and you might have either a hot or gound wire loose in that plug.

Posted by Ian Bailey (Member # 1752) on 01-28-2008, 04:22 AM:

Hi Michael
I submitted another photo of me holding a bloody big fish I caught right out the front of my house......but Brad doesn't seem to like having more than one person in the photo [sex]

......so now you've ended up with my bloody ugly head!!
I'm semi retired at the moment(and very poor!!) so most of my time is spent at home doing house duties while my lovely wife slogs it out at The Pickle Factory to make a few peso's.
I could send a "Tuesday's" shot of me which is Nude Ironing Day!
[Eek!]

Monte
That was going to be my approach to this.....check connections from Red Led to CSP1200 inputs.I know the shielded cable to the CSP1200 input runs in some couduit with a few other nasties....amd there is a join in the cable.
The Reader power supply was replaced not that long ago and the led was replaced recently(by a service tech).
I have had problems before with the wiring connection for the Led housing.
What was unusual to me was the way the hum would increase with dialogue....not sure if I'm missing the obvious here but this seemed wierd to me.
I did run a Buzz track and set Dolby level without any improvement.
Will let you know how I go.....after Tuesday [Big Grin]

Cheers Ian

Posted by Gordon McLeod (Member # 33) on 01-28-2008, 05:53 AM:

I would disconnect the led and see if the hum is still there as you mention that the hum increases with changes in the track volume
I would suspect if that is verified that there is some AC on led current
Also is the hum present in non sync or digital

Posted by Ian Bailey (Member # 1752) on 01-28-2008, 06:38 AM:

Hi Gordon
I'll try disconnecting the led......I think you could be on the right track here as I did notice that when I turned the led off there was a small residual glow.We have a toggle switch which we use to turn the led off for a No Show.....I know this could be done through the automation but haven't got around to that one.
I'll measure the voltage at the connector for the Led housing....so what your saying is there should be no AC voltage here? I'll also check the wiring terminated on the power supply to see if that's OK(no wires touching etc)
Non Sync and Digital work fine,,,no hum.
Cheers Ian