This is topic Can't Get Rid of the "Waw" Sound in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Manuel Francisco Valencia (Member # 710) on 06-26-2002, 03:45 PM:
The machine is the P35GPS. My problem is I can't get rid of what is commonly referred to as the "waw" sound distortion. It is usually caused by improper threading but I have ruled that out. How exactly have I ruled that out? I have threaded it myself with little tension and a lot of tension. I even adjusted the gear in the back for the constant speed assembly to give me every degree of tension in between. No results. There was a lot of vibration in the guiderollers and the drum so I changed the bearings on the rollers and that cut out the vibration a little. I also lubed up the belts a little and that helped a little bit more. When I roll the drum and rollers without film it sounds like one of the rollers has a bump on it or something because I can hear it come off the drum and land back on but I can not see this happening or the flaw on the roller. The rollers and LED are in alignment and cleaned so I can not think of anything else that could be causing this. I did not notice it until recently because we have DTS in that house and it reads fairly well. This weekend however we recieved a bad print of Minority Report with a few dropout points in it. Does anyone know what I am missing?
Posted by Brad Miller (Member # 2) on 06-26-2002, 04:01 PM:
Did you change the bearings on the actual drum shaft itself?
Posted by Randy Stankey (Member # 64) on 06-26-2002, 04:35 PM:
I second that one! Been down that road many times! 
Posted by Paul G. Thompson (Member # 655) on 06-26-2002, 07:23 PM:
I have heard that sound in House No. 4 in Stanwood. When it happens, I noted it partially lost the tension around the scanner drum. When I put my fingers on the lat guide roller and damper, it felt like a freight train going through. I believe you need a belt change, as the scanner bearings were, in my case, in excellent condition.
Posted by Brad Miller (Member # 2) on 06-26-2002, 09:05 PM:
If the bearings are all in good condition, you should be able to thread the soundhead with a couple of perfs less than zero tension, so there is a bulge of the film as it enters the sounddrum. If when threaded in that manner the film runs smoothly without bouncing, the bearings are fine. If not, the bearings are shot.
Posted by Manuel Francisco Valencia (Member # 710) on 06-27-2002, 01:42 AM:
I moved the drum and did not hear anything or feel any vibrations. When threaded with less than zero tension there is a steady loop between the middle constant speed asssembly and the drum so I am assuming by Brad's statement that the bearings are fine. When threaded with tension I get more shaking of the film thatn with no tension. As a quick fix to help the sound I would put a rubber band around the ends of the two lateral guide rollers to put a lot of tension on the film. I do not like this because I know that is way to much tension but like I said it was a quick fix. But this has lead me to the springs. They feel as strong as all the others but is there a way that they went bad that I am not noticing?
Posted by Paul G. Thompson (Member # 655) on 06-27-2002, 01:51 AM:
What kind of shape is the dash-pot (damper) in?
Posted by Brad Miller (Member # 2) on 06-27-2002, 04:50 AM:
Manuel, after reading your last post, I think Paul has now pegged your problem. I'll bet your air pot shaft is broken. Take a looksee and let us know.
Posted by Carl King (Member # 398) on 06-27-2002, 11:14 PM:
If you're using Cinemeccanica Vic 8 machines it may be the clutch
behind the sound drum. Remove the cover on the non-operating side
and screw the shaft in 4 or 5 turns.
Posted by Manuel Francisco Valencia (Member # 710) on 07-05-2002, 10:35 PM:
Been awhile since I have checked back in. Actually checking the pot totally slipped my mind. The shaft is in good condition so I adjusted the pot but that still has not helped. Could the Mid Constant Speed Assy. be out of alighnment with the everything else?
Posted by Paul G. Thompson (Member # 655) on 07-06-2002, 01:04 AM:
Manuel, are you sure that the lateral guide is adjusted correctly? Could you be hearing sprocket perf clip? (96hz) If I tune the "waw" in my mind, I come up with 96hz. Is it constant in pitch? Does a splice passing through have any effect of the loudness, even for a split second? I'll almost bet your lateral guide or reader is out of alignment. By the way, is it still a constant sound of the same level throughout the entire dynamic range of the sound track modulation?
Run a buzz track through that thing and see what you hear. If the guide is properly aligned, you will hear nothing, except maybe some random noise because of dirt specks on the sound track. If you hear some kind of a tone, the lateral guide or something else is definately out of alignment.
If you don't have it cured by time Josh and I come down to Texas, we'll stop in and cure it for you, ot at least find out what is causing it.
By the way, if the scanning beam hits the DTS track, it'll make one nasty sound that would pucker your ears... 
Posted by Jason Black (Member # 684) on 07-06-2002, 01:23 AM:
After replacing all of my soudn drum shaft bearings, I'm willing to bet my job that they will be the culprit you're looking for. I have done the rubber band method as well when dashpots were not broken, and when they were to cure the WAW sound you mentioned.
Posted by Paul G. Thompson (Member # 655) on 07-06-2002, 01:32 AM:
After reading Jason's post, he discribed the sound I heard in No.4 at Stanwood. I was able to correct that the way Jason did. But I am not so sure that is what Manuel was hearing. Manuel, if you can send me a short MP3 file for me to listen to, that would be helpful.