Film-Tech Forum ARCHIVE: Sprocket hole noise

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Posted by Robert Throop (Member # 61) on 04-25-2006, 06:51 PM:

I'm installing a CP50 and CE ASR40 readers in a changeover booth with Simplex SH 1007 soundheads. There are no problems with the #2 machine. #1 however has what seems to be sprocket hole noise. I've run buzz track with two straight lines on the scope. Cat. 97 shows no cross talk yet when I play program material there seems to be sprocket hole noise on the quiet sections. Any thoughts?
Thanks,
Bob

Posted by Floyd Justin Newton (Member # 1316) on 04-25-2006, 06:57 PM:

Robert--

There is a lateral adjutment in your soundhead OR your slit
width may be a 'hair' too wide,

Posted by Steve Guttag (Member # 268) on 04-25-2006, 08:11 PM:

Red reader or exciter lamp?

Do you have Dolby Digital basement readers?

If you have red readers, what you are most likely looking for is a reflection/scattering of the red light being modulated by the perforations, not necessarily a direct line. Using a business card you can often find where it is coming/reflecting from...sometimes off the chamfer of the drum.

If this is an exciter lamp system then th eproblem is most likely the pinch roller assembly. It is probably not hitting square on the G-1985 pinch roller. To verify, thread buzz track. Verify all are perfect. Then apply more pressure the the pinch roller in an even manner in the center of the bracket...if the buzz track does not change, all is good, if it does, the bracket has issues. Look for a crack in the barcket where the part that holds the roller and bearings joins to the part that has the pivot pin go through...the crack will be only in the upper bracket.

If you can take the film out and look at how the pinch roller hits the drum (use a flashlight from below and possibly a dental mirror to get a good view). The pinch roller has to hit the drum squarly and not favor either side.

Lastly, make sure the return spring on the lateral guide roller/pinch roller really is in charge of the film by having it push against the fixed roller.

Steve

Posted by Louis Bornwasser (Member # 3063) on 04-26-2006, 03:28 PM:

Adding to Steve's post: If it is a reflection on a basement reader, disconnect the digital LED and the noise should go away. If this is the case, there is a "cover" available from Kelmar to stop the reflection. Louis

Posted by Richard Fowler (Member # 893) on 04-26-2006, 03:44 PM:

The CE ASR-40S reader has a press fitted lens tube to the chassis versus the more accurate threaded tube on the 30S series which may be a cause for the problem...this is after alinement, drifting parts on the Simplex head, poor release print, missing paint leaving bright bright spots of copper on the led mount, are considered....

Posted by Darryl Spicer (Member # 711) on 04-27-2006, 10:04 AM:

Don't forget that crazy dts timecode that is positioned in an area that test film would consider ok. I wonder why they don't just put a time code on the alighnment film to insure you don't pick it up.

Posted by Robert Throop (Member # 61) on 04-30-2006, 11:44 AM:

Thanks for all the replies. I think I finally fixed it although I'm not sure why. I tried moving the led around and I was not able to eliminate the noise. Yesterday I swapped leds between the two machines and voila! The noise is gone.
Bob