Hello everyone. I am having a bit of trouble with my second microscope (the one I was starting to assemble when my current already-complete scope came up for sale at an unbeatable price), and I'm hoping it's a straightforward solution.
The scope has a Gemolite Mark V base with an AO head (I replaced the original 569 with a 580)--it works great except that the focus drifts down with gravity (it did with the original lighter 569 head as well). I've looked at the screws on the focusing rack (or whatever you call that) and they all seem to be totally tight, both the four hex screws on the outside and the two flatheads in the center. The track portion seems to be bowed out, flush with the metal at both flathead screws but with a gap in between.
Anyone have any idea how to fix this? Thanks for reading.
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Post subject: Re: Gemolite Mk V maintenance question
Posted: Sun Mar 04, 2018 5:47 pm
Platinum Member
Joined: Tue Jan 02, 2007 8:20 pm Posts: 2659
The space under the rack gear is supposed to be there. It limits the pressure of the pinion gear on the rack so that the rack does not get milled out when the lube gets dry. Try turning the knobs in opposite directions. Often there is an adjustable (by turning the knobs in opposite directions) friction clutch that just needs to be tightened. If the knobs don't do that you have to look for some little screws that adjust the friction either on the pinion shaft or on the dovetail. These may be in the back or the side. They apply pressure to the dovetail and prevent sliding. There are focusers that don't have either mechanism which rely on grease friction. If that is the case you have to look up a lubrication seller and find a non voltatilizing (if possible) stiffer grease to reduce the tendency to slide.
Whoops, I thought I'd already updated this post with the additional information. This will sound dumb but tightening that top flathead screw actually did work--the problem was, because I didn't have a slide across the darkfield well I was testing it by focusing on the black darkfield cover, which is way below the range where the scope is supposed to work. In the normal range it is now tight and firm. I assume this is how it is meant to be given the bowing. Thanks though! I really appreciate your posts here and elsewhere, they have been a great resource.
Post subject: Re: Gemolite Mk V maintenance question
Posted: Sun Mar 04, 2018 6:26 pm
Platinum Member
Joined: Tue Jan 02, 2007 8:20 pm Posts: 2659
If you are way out of range mainly when you are up too high there may not be enough stiction to hold it even with the correct grease. Not enough surface area. That is why they invented boom stands and long travel rod stands.
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