Film-Tech Forum ARCHIVE: Question on Century Pressure Bands

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Posted by Ethan Harper (Member # 472) on 08-05-2004, 02:15 PM:

Is there a way to loosen these? Though they are set to it's minimum tension on the adjustment knob, they still feel pretty tight.

Posted by Mark Gulbrandsen (Member # 72) on 08-05-2004, 05:09 PM:

Assuming the bands are new and assuming you have the 4" lens mount version SA check for .25" of clearance between the plate that the curved runner mounts to and the surface of the studio guide on the trap. Use the shank of a .25" drill bit to do this. If this clearance is set right the tension will be within spec. I usually find a Century produces the steadiest image with best focus at about 1 to 2 o'clock on the tension knob.
Hopefully you will have the correct clearance Clarence.

Mark @ CLACO

Posted by Tony Bandiera Jr (Member # 2365) on 08-05-2004, 07:28 PM:

Mark:

Been quite a while since I played with that clearance on a Century, how is it reset? If I remember right, it was done by losening the setscrew holding the gate closing knob/spring assy and turning it slightly clockwise to unload the spring....hmmmm?

Or am I barking up the wrong tree? [Confused]

Posted by Ethan Harper (Member # 472) on 08-05-2004, 08:30 PM:

The gate is where it is supposed to be. My question is how to further loosen the pressure bands on the trap, they feel very tight and un-springy even with the adjustment knob set at 12o'clock.

Posted by Mark Gulbrandsen (Member # 72) on 08-05-2004, 09:16 PM:

Ethan,
There is something else wrong with the trap, perhaps a stuck top band attach arm or some crud causing the tension to be pulled only to one side. Sometimes those little attach arms at the top of the trap which are supposed to be able to pivot do get stuck and cause this. Also are both bands the same type and in good shape? New hopefully...... Take it apart and clean it well and re-assemble and see how it is then. A stuck attach arm is all I've ever seen that can cause this problem though. Be aware there are very small parts there, very small c-clips or snap rings depending on the vintage of the SA. his is work to do in a brightly lit area and on a work bench.

Tony,
To set the trap clearance you loosen up the four screws that hold the entire open/close assy(casting) to the main frame. Two screws on top and two below. The top screws are located immediately to the left of the lens eccentric adjustment. With the whole assy loose and the gate in the closed position slip in a .25" drill bit and then slide the whole assy back to clamp the drill bit in place. Tighten the screws up when its at that point and you're done. Double check that the top and bottom clearances are the same.

Mark @ CLACO

Posted by Tony Bandiera Jr (Member # 2365) on 08-07-2004, 01:32 AM:

Mark: [beer]

Thanks!! It'll be helpful in the near future, just picked up a theatre to service with Century's and the guys around here had not a clue what to do.