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Electronic Theatre Controls Inc

fos/4 Fresnel Doesnt Hold Focus When Pointed Down


A fos/4 Fresnel or Desire Fresnel may lose its flood or spot zoom focus when pointing straight down, especially if a barn door or other heavy accessory is attached.

Explanation of Issue

Early models of these fixtures used short springs in the zoom knob to hold the fixture's zoom in place.  Initial testing showed that these were sufficient to hold position.  

Real world use showed that if accessories are attached to the front of the fixture, the fixture could become heavy enough that these springs could no longer maintain the position of the zoom, and the fixture's focus may drift.


To resolve this issue, new fixtures use longer springs in place of the original, shorter springs.  This increases tension and allows the fixture to hold position.  This change was rolled into production on December 2, 2021.  Fixtures manufactured after this date should not experience this issue.

Link to the replacement guide here: Click Here

If you have a fixture manufactured before December 2021, a retrofit kit has been made for you to easily replace your springs.  This can be obtained under warranty if needed- ETC will simply need to confirm the manufacture date of your fixture based on its serial number.  The kit is ETC part number 7470K1004.


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