Optical spectrum analyzers slit failure

[jfphp]

Back on an old un-answered question : I have now several OSA (HP, Advantest) and they all have a permanent or intermittent slit failure. I understand that all these OSA use a very precise motor driven panel with various width slits to get the resolution of the light signal but I wonder about this very commun failure : dust in the slits, grease oxydation in the motor gears, backlash ? Any answer welcome !

[_Wim_]

Cannot confirm the slit failure, but I had a broken Anritsu MS9710C with a grating failure (so also a motor driven component), and this was fixed by simply reseating all corresponding connectors. It seems many of these OSA were used on the road, and have been subjected to vibration during transport. So that at least could be a possible cause.

It could also be that this is one of the first things that is checked during the initial self-test, and when it fails, no other tests are performed.

[masterpj55]

curious about this too. it's the most common error i see on units.
I dont really understand the internals of these units yet but I doubt it's many common components.

[cosmo little]

I also have an HP70952B with intermittent slit failure error. After switching on and off a few times the error goes away. There is a picture of the internal construction of the 70952 family in the HP Journal Dec 1993 ( available on line)
  The slit wheel is driven by a small motor, possibly a stepping motor. I suspect that the lubricant used thickens over time so the motor cannot turn the slit wheel.

  I suggest that someone with a completely dead unit takes it apart and investigates. There is no service manual available. I am reluctant to take mine apart as the slit wheel is inside the sealed compartment.

A full tear down with video would be really useful. Perhaps someone could send a dead unit to Dave?