The most common error which will render your Canon lens unusable is to mix up the servo control attachment screws.
Should you have reason to replace such screws it is essential to put the the long pair into the correct holes . If you get this wrong and put one in the wrong hole it will go right through and squash the Zoom cam unit.
This can sometimes be repaired but the cost will generally exceed £400-00 . If the damage is so great that the cam cannot be saved expect a much bigger bill, if you can still get the parts.
