When you say power supply voltages are OK, I asume you mean the image Intensifier power supply voltages!
Are the images blurred on Full Field & Zoom? If yes then the mechanical focus needs to be adjusted. If the answer is no, then you have an II power supply problem.
You can check/compare the II power supply voltages with the factory test certificate if you have one in the service manual.
Mechanical focus: First you must release the focus locking screw and then adjust focus ring.