Electromagnetic Lens Repair

Hi,

I am not very sure whether this is the best suited forum for my query
but still I am sure this is not totally off-topic. So here goes..

Our 1990-purchased JEOL 6400 Scanning Electron Microscope recently
developed an intermittent problem of black bands randomly
appearing/sliding on its display.

This was traced to an oscillating 24V supply powering, among other
things, its objective lens control board and the objective lens
itself. We found both ends of the objective lens (basically an
elaborate coil of insulated copper wire wound on a conical steel(?)
core) winding were at ~1 ohm to the the instrument chassis while the
coil itself ~2ohm across.

Disconnecting the lens has stopped the supply oscillation etc but
ofcourse now there is no image!

We are guessing that either the condensation due to the running
cooling water or the heating due to lack of it has shorted the
innermost layers of winding to the core.

While we are still hunting for a spare, I would like to enquire people
here for pointers on design & rewinding of electromagnetic lens coils.
The winding looks specially designed - with number of turns decreasing
in each layer in a particular fashion as one goes up the core.

Will just replicating the winding - wire gauge & the turn pattern -
bring it back to function?

Any info/pointers highly appreciated!

--
tia,
Aniruddh Sarkar
Research Associate
Dept of Electrical Engg
IIT Powai
Mumbai, India
.

Relevant Pages

  • Re: Electromagnetic Lens Repair
    ... its objective lens control board and the objective lens ... >elaborate coil of insulated copper wire wound on a conical steel ... If the windings are indeed wound on a magnetic core, ... distribution of the windings on it. ...
    (sci.electronics.repair)
  • Re: Electromagnetic Lens Repair
    ... its objective lens control board and the objective lens ... > elaborate coil of insulated copper wire wound on a conical steel ... > innermost layers of winding to the core. ... While I'm not an expert on SEM design, ...
    (sci.electronics.repair)
  • Re: JEOL 6400 Objective Lens Repair
    ... >Our 1990-purchased JEOL6400 SEM recently developed an intermittent ... >This was traced to an oscillating 24V supply powering, ... its objective lens control board and the objective lens ... The coil is usually inset from the ...
    (sci.techniques.microscopy)
  • JEOL 6400 Objective Lens Repair
    ... This was traced to an oscillating 24V supply powering, ... its objective lens control board and the objective lens ... innermost layers of winding to the core. ...
    (sci.techniques.microscopy)
  • Re: Electromagnetic Lens Repair
    ... then I guess you are stuck with rewinding the coil. ... of wire are the same for each layer as in the original coil. ... its objective lens control board and the objective lens ...
    (sci.electronics.repair)
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