Film-Tech Forum ARCHIVE: Having some sound problems.....

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Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:05 AM:

At one of our theaters here in town we are having some sound problems. This is what we have. CFS LX2500 console, Simplex 1050 projectors with 5 star sound head. Using jax light with Ultra Stereo procesor. Prcessor is equivilent to the JS 200 series.

The problem is extreem noise in all channels. Sounds like it does when you try to manualy strike a lampe only continuously.

What I have done. Basically replaced all the cards in the processor with ones from another machine. Problem still there.

Problem does not exist in nsync. Only in stereo. Noticed that when you turn on the exciter manually the noise is there and I noticed that the led's on the noise reduction card were pegged out in the red. I changed the signal amp on the cell lines it did not fix the problem. The LED is bright and looks good on the jax light. Problem exists even with the jaxlight out of the sound head. Jax light is powered using a 6volt dc transformer, I think it is 6 I can't remember of the top of my head, that plugs straight into an outlet in the back of the console. I worked at that theater for 8 years and never experienced anything like that before when I was there. Very strange any suggestions that I may be able to do or have them do. Our tech is on vacation till Monday and the closest one to use is in North Carolina.

Posted by Joe Morris (Member # 1553) on 03-08-2003, 12:09 AM:

what kind of noise are you getting? static or hum? or buzz? or twinkle twinkle little star?

Posted by Brad Miller (Member # 2) on 03-08-2003, 12:13 AM:

Start by removing the solar cell leads to the "proj1" input of the Ultra Stereo. (Make it a point to write down which wires went to which terminals before you do this and have the Ultra Stereo powered off when you do.) Now switch to stereo. Is it still there? If so, then it's in the processor. If not, it's in the Jaxlight. Odds are it is the Jaxlight as lots of people have problems like you describe with them. Once we know which it is, report back and we'll further diagnose. [Smile]

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:14 AM:

hmmmmmmmmm how to describe it. you know how AM sounds when it is not on a station or when you pass near power lines. I guess that is the best way to decribe it.

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:17 AM:

thing is though It was doing it without the Jax light in the sound head. Socket removed and everything.

Posted by Jack Ondracek (Member # 1466) on 03-08-2003, 12:23 AM:

Has anyone installed a hardware-store-type light dimmer in your place lately?

Posted by Chris Markiewicz (Member # 1415) on 03-08-2003, 12:24 AM:

Could be a ground loop. Check that the lines from the solar cell have the shield grounded only at the processor, not at the soundhead. Even one loose strand touching ground will do it. Drove me crazy when I put in the LED reader.

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:29 AM:

No nothing like that has been installed. I know what you are saying though we had to ground some of the machines in two places to eliminate buzzing that dimmers were causeing but this was not the same type of noise. I have a feeling that the cell lines may be picking up A/C voltage leakage from something and amplifying it into the processor. Could a DC transformer like you would use for a calculator or something possable be going bad inside causing A/C leakage or something. I didn't think about changing that DC plug until I got home and the theater was closed.

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:32 AM:

I did check the grounds. Everything fine there. Oh one thing. THe projector was not running when I was checking things.

Posted by Marc Jones (Member # 29) on 03-08-2003, 12:47 AM:

Isn't there a small amplifier on the solar cell inputs from the Jax light into the processor? If there is I would verify all of the connections are good or possibly swap the module with another screen.
Good Luck

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 12:51 AM:

I did that too....Thanks for the suggestion.

Posted by Fabrice Dubourg (Member # 1635) on 03-08-2003, 01:37 AM:

ground loops problems, maybe, as i can't hear what it sounds like...
is the buzz constant or does it appears from time to time?
Did anyone made some works in your theatre the days before your problems occured, like electricity work, neon sign?
is there in your theatre a neon light blinking due to a starter problem? i had this problem once...
is my english understandable ??

Posted by Bill Langfield (Member # 818) on 03-08-2003, 08:01 AM:

What the hell is a Jaxlight?

Darryl,
Try replacing the CP's PSU unit.
Thats what went wrong on a cp65 to me the other day.

Bill.

Posted by Rick Long Jr (Member # 541) on 03-08-2003, 09:26 AM:

You say it's there only in stereo. How about Mono? Could it be the NR card in the processor? I've had a few Cat 222's do similar things over the years.

Posted by Joe Morris (Member # 1553) on 03-08-2003, 12:12 PM:

I'm running a JS 200 in my theatre as well..and I have had similar problems with noise as you describe. I tried the ground loop, tried the cards...and the only other thing that I could come up with was that we are getting a TON of interference. We have buzzes...hums....static....the theatre that the 200 is in has THE worst presentation of all. I had 2 JS 105-95's in my 2 biggest houses...both of them had problems similar to what you are describing...both running Jaxlights. I replaced the first with a 200...still had problems...second with a Panastereo CSSP 1200....no problems...it could just be something interfering with the processor...or it could just be a bad NR card like Rick said...but if your Jaxlight is bad like Brad said, you probably wouldn't get any sound at all.

Posted by David Stambaugh (Member # 1102) on 03-08-2003, 12:56 PM:

JaxLight

Posted by Darryl Spicer (Member # 711) on 03-08-2003, 03:47 PM:

Ok, I returned to that theater today and the problem is gone now. I added an extra ground to the ground point at the line amp grounding it to the soundhead. This has help us on other situations. I also talked to our tech in North Carolina and we are both in agreement that something was being amplified over the line to the processor. As to what was being amplified is the big question. Since it had gone away over night we think something may have been in a thermal overload situation but we are just not certain at this time. I did remove the cell wiring and all normal noise that can be picked up was gone but since the noise related to the problem was not there I can not determin if it was related to the cell wiring or something else. They are keeping an eye on it. Will let everyone know what happens if anything and what we determin to be the problem. These are the kind of problems that will make you pull your hair out and go grey very quickly. [Smile]

Posted by Bruce McGee (Member # 131) on 03-08-2003, 05:21 PM:

I have a small signal amplifier that uses a small 9v DC power supply that plugs into a standard outlet. I was having all kinds of odd problems: hum, crackling, whistling sounds, etc. I replaced the power supply, and instant cure. I put up with this problem for almost 3 weeks while I was troubleshooting the amp. Never figured the PS to be bad, though. After I got the replacement unit, I dissected the old supply. One small transformer, diode, resistor, and a capacitor. The cap is discolored. I'm glad I got the new one.

I hate intermittent problems. Makes me want to rip-out the rest of my hair.

Posted by Don Bruechert (Member # 1538) on 03-09-2003, 12:21 AM:

One way I have solved sound problems in the past that were power related is to do a "ground lift". The easiest way to do this is to take a cheap 3 prong adapter for the AC line and break off the ground connector so it doesn't touch anything. Now plug your unit into that, and the adapter into the AC. This effectively removes the ground connection through the power system without having to cut off the ground pin on the plug. Sometimes noise can come in via the ground, or if your components are on different phases in a 3-phase system you can have current flow on the grounds - this can also eventually wreck equipment. You will notice that many professional sound companies for bands will connect their own power distribution system and run cables to make sure all of the components are connected and grounded in the same place. I realize nothing has changed in your place lately, but this noise could be coming from a refrigeration unit that is failing, a furnace or fan motor with problems, or almost any other piece of equipment that was running the day you had the problem but not when you came back...