ST Imaging Viewscan Service BulletinST engineering has been investigating an issue where 3 of our customers have experienced take up motor failures over the last 15 months. We have been testing VS II and VSIII systems for film movement between the glass platens and the 2 Mylar strips and motor stress and this is what we have found.
The ViewScan system is designed for the emulsion side of the film to be down. There are 4 spacer buttons which are 0.022 inch thick that creates the space between the glass. The 2 Mylar strips are 0.015 inch thick and are used to create a gap between the film and the top glass. This combination creates a theoretical remaining gap for the film of 0.007 inch which we verified by measurement on multiple ViewScan II units. When running 0.005 inch thick film, that only leaves 0.002 inch clearance (the diameter of a single hair on your head)...not much! Continuously in contact with the film moving forward and reverse, the strips act like wipers collecting all the dirt and debris from the film and depositing it along the leading edges of the strips.
When there is sufficient buildup of dirt, the movement of the film draws the debris under the strip which in turn forces the emulsion side of the film down hard against the surface of the lower glass (where it should never touch), concentrating all the force in one small area, and eventually scuffing and scratching the glass while leaving sticky emulsion deposits which further reduce the gap where the film travels. Over time and layer after layer of buildup, the gap shrinks to nothing, and more and more friction (drag) is added to the film movement which the reel motors now must overcome. The motors run hot due to the constant added load and eventually fail prematurely. The Mylar strips were added to the ViewScan I in 2012 to eliminate moiré patterns picked up by the camera only when using certain thin films reported by some users. The top glass has not changed since.
With the testing of the ViewScan III we have determined that the combination of optical glass, LED lights and new camera that we do not need the black spacer strips on the left and right side of the top glass. New units will not ship with these strips on the glass. Note: About 40 units of VSIII were shipped before this change took effect so please remove them at time of installation or on your next visit.
In some instances it has been reported that the film in use as part of their collections could be improperly facing the emulsion side of the film towards the top glass, even when the film roll is installed properly. The ViewScan system is designed for the emulsion side of the film to be down. If you have customers with any kind of motor problems or If you find any signs of wear on the bottom glass below the strips, or find that the film does not pass easily under the strips and the motors seem to drag or slow down at times, this could result in damage to the film and motors. We recommend removal of the black antistatic strips that are on the underside of the top glass. Through our testing on VS II we believe that the strips are not required and we recommend you remove them on you next visit to the customer.
To remove the strips, use your finger or razor blade to pry up one end of the strip until you can grab it and remove it. Be sure to clean any adhesive residue thoroughly from the glass, an alcohol wipe or Goo Gone will do the job nicely. Then clean any dirt build up off the lower glass. Note: it may require a razor blade to scrape it off.
We also now recommend that users clean the glass weekly to ensure there is no build-up of dirt on the glass. System usage should ultimately dictate clean frequency.
If you have a customer how experiences any moiré patterns please contact our support desk