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Stereozoom microscope repair

Discussion in 'Electronic Design' started by Chuck Olson, May 2, 2005.

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  1. Chuck Olson

    Chuck Olson Guest

    I know, I know, send it back to the factory or to a repair center. But that
    costs money, and I don't learn anything if I do that.

    I have a couple of 0.7 to 3.0 Bausch & Lomb microscope pods that are messed
    up - - one white one that requires eye convergence for less than a foot away
    to superimpose the images, and a black one I just bought that is okay
    horizontally but has a vertical offset. They don't look like they were
    dropped or anything, but the left eye optical path seems different from the
    right eye path. It may be my imagination, but the right side of each
    instrument looks good.

    I think just about any technician or engineer who needs to work with today's
    surface-mount technology needs a good zoom microscope, so there must be a
    lot of them around. I paid $15 for the black one today, complete with stand.
    Okay, I should be able to afford some repair expense to put this thing back
    in shape, but what's it going to go for after it's fixed - - $100? Can I get
    it repaired for $85? I don't think so. And I Google-searched all over for
    some hints as to how to adjust or repair this brand of microscope, but
    there's not a single post that I could find that was any help. I guess all
    the repair techs have signed a non-disclosure agreement or something.

    Getting down to business, I opened up my black $15 microscope and found a
    series of mirrors in the section that allows interpupillary adjustment, and
    two movable lenses on each side in the zoom section. The mirrors all appear
    to be positioned by contact with machined surfaces on pivoting aluminum
    castings. It doesn't look like these can move around unless one breaks loose
    from the glyp they put around the edges of the contact areas. Looking into
    the empty eyepiece holes, the left eye sees a bright elongated spot (8 to
    10% of aperture area) outside the aperture at about 10:00 at all zoom
    settings that is not present in the right eyepiece hole - - looks like a
    sneak path or a chip out of a mirror. The image offset of the left when
    eyepieces are in place is about 1/6 of a field diameter low compared to the
    right, and could be converged with eyesight set for 6 ft away, if the
    vertical offset were not present. This offset is exactly the same at all
    magnifications. The white microscope behaves exactly the same at all
    magnifications, also.

    In the zoom section, turning the zoom control rotates a pair of cam shafts
    grooved for pins that drive Nylon pads along guides. Each lens is fastened
    to its Nylon pad by a couple of screws, and it appears possible to adjust
    lens tilt by loosening the screws a bit. I have resisted the temptation to
    see what happens when the screws are loosened, but is this the only
    adjustment for optical convergence we have? It looks pretty sloppy and
    difficult to control.

    So have any of you dug into your microscope and figured out how to fix it?
    Do any of you with B&L training care to guide an old EE to make something
    good out of the junk he finds at a flea market?

    Thanks for all your help,

    Chuck, w6pkp
  2. I don't know about the Bauch & Lomb models, but the old Vickers 'Zoomax'
    could give vertical displacement if the rotating eyepiece turret was not
    returned to exactly the correct position before locking it up.

    Before taking your instrument apart, just check to see that the turret
    hasn't been turned a few degrees by mistake.
  3. I recently recovered a B&L stereo zoom enough to be useful.
    The deterioration was caused by volatiles from the grease used on the
    focussing track depositing on the optics.
    Simple cleaning was inadequate so kill or cure I applies metal polish
    abrasive carefully to break up the varnish like layer, it worked , with
    good illumination contrast is sufficient to use for sm assembly
  4. Boris Mohar

    Boris Mohar Guest

    I have the same microscope. The deposits on the objective lenses is the
    solder flux condensing. Just take it off with flux cleaner.


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things)
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