Film-Tech Forum ARCHIVE: Can't Get Rid of the "Waw" Sound

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Can't Get Rid of the "Waw" Sound

Author

Topic: Can't Get Rid of the "Waw" Sound

Manuel Francisco Valencia
Expert Film Handler

Posts: 151
From: Oklahoma City, OK, USA
Registered: Dec 2000

posted 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?

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-26-2002 04:01 PM

Did you change the bearings on the actual drum shaft itself?

| IP: Logged

Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 06-26-2002 04:35 PM

I second that one! Been down that road many times!

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 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.

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 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.

| IP: Logged

Manuel Francisco Valencia
Expert Film Handler

Posts: 151
From: Oklahoma City, OK, USA
Registered: Dec 2000

posted 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?

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 06-27-2002 01:51 AM

What kind of shape is the dash-pot (damper) in?

| IP: Logged

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 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.

| IP: Logged

Carl King
Expert Film Handler

Posts: 199
From: Saint John, New Brunswick, Canada
Registered: Mar 2000

posted 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.

| IP: Logged

Manuel Francisco Valencia
Expert Film Handler

Posts: 151
From: Oklahoma City, OK, USA
Registered: Dec 2000

posted 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?

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 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...

| IP: Logged

Jason Black
Phenomenal Film Handler

Posts: 1723
From: Myrtle Beach, SC, USA
Registered: Nov 2000

posted 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.

| IP: Logged

Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 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.

| IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.