General maintenance methods and repairs of laboratory biological microscopes

Maintenance method:

1. The biological microscope should be placed in a dry and clean room to avoid mildew of optical parts, rust of metal parts, and dust. After using the microscope, put it back into the box (cabinet), or cover it with a glass cover or plastic cover, and put in the desiccant.


2. Do not disassemble the parts by yourself. An Eyepiece or eyepiece cover shall be inserted into the lens barrel to avoid dust entering the lens barrel’s upper part. Don’t touch or wipe the lens surface with your fingers. If there is any dust, gently brush it with a soft brush, and then wipe it with a soft clean cloth. You can also wipe it with mirror cleaning paper dipped in a little xylene or petroleum ether, but be careful not to draw stripes on the lens surface. If the lens is mildly mildewed and cannot be wiped with paper, it can be gently wiped with a cotton swab dipped in a mixture of 70% ethanol and 30% ether.


3. Biological microscope should not be put together with corrosive acids, bases, or volatile chemicals to avoid corrosion and shorten service life. In principle, when observing the specimen containing liquid, it is generally necessary to cover the cover glass. If the liquid contains acid, alkali, and other corrosive chemicals, the surrounding of the cover glass should be sealed with paraffin or vaseline and then observed. However, this kind of reagent is often used in the microscopic identification of traditional Chinese medicine. It is impossible to seal all of them. Therefore, special care should be taken to prevent the liquid from flowing onto the stage, let alone the objective lens.


4. Biological microscopes should not be exposed to direct sunlight. Nor should they be placed close to the furnace or heating to avoid the degumming, deformation, or damage of lens and mechanical parts caused by excessive cold and hot changes.


5. The cleaning objective is limited to the outer surface. After drugs contaminate the object’s surface, wipe it with a little mirror wiping paper (do not use alcohol). If the back needs to be cleaned, wipe it with a soft brush, or use a leather suction head to remove the dust.


6. Rotate the coarse focusing more slowly than the fine focusing, do not crush the cover sheet.


7. After using the oil lens, the cedar oil on the lens must be wiped clean (the lens paper can be dipped in a little xylene to wipe. But attention should be paid to the xylene not penetrate the interior of the lens. Otherwise, xylene dissolves the adhesive between the lenses, which can make the lens fall off).


8. The mirror surface of the mirror should be protected and clean, and water, xylene, or cedar oil should not be penetrated to avoid the mercury falling off the mirror.


9. If the mechanical part is not flexible. You can use fine silk cloth dipped in xylene a little: wipe off rust and grease, and then use a little liquid paraffin lubrication; do not twist too tightly to avoid damage.


10. Sometimes, if stains or foreign bodies are found in the field of vision of the biological microscope, the eyepiece can be rotated first. If the colors follow the rotation, it can be determined that the stains are on the eyepiece; otherwise, the specimen can be moved. If the stains follow the movement, the stains are on the specimen. If both are not, the stain is on the objective lens. Check the front lens of the objective lens first, and then the rear lens. Clean according to different conditions.


Sometimes a part of the field of vision is not clear. It may be due to fingerprints or dust on the surface of the front lens of the objective or eyepiece; or the specimen is not well made; or the microscope is not used properly. For example, the lighting system is not adjusted correctly. We should find out the situation and solve it separately.


11. After the use of the biological microscope, all parts should be wiped clean. Then the objective lens should be turned into an octagonal shape. The lens barrel and light collector should be lowered and fixed, and then the mirror of the reflector should be placed vertically.

Common Troubles Repair:

The microscope is the most commonly used instrument in biological experiment teaching. After frequent use, there will be some failures, which make the microscope unable to operate normally. Because a microscope is a precise and valuable instrument, it is impossible to add and update it. Therefore, it is very important to remove the fault in time and keep it in good working condition—the following microscope some standard troubleshooting, for your reference.


1. Rough adjustment failure

The trouble is that when the coarse quasi-focus screw is rotated, the lens barrel can’t rise and fall with it.


The rack driven by the gear realizes the lifting of the microscope tube. The gear fixed on the rotating shaft of the coarse adjustment knob, and the rack is fixed on the tube. When the coarse adjustment knob is turned, the gear drives the bar to lift the lens barrel. If the lens barrel can’t rise and fall with it, it means that the gear and rack don’t match. The common fault reason is that the toothed rod sleeve rotates with the coarse adjustment knob; that is, the two stop screws on the toothed rod sleeve do not fix the toothed rod sleeve the dovetail guide rail.


Repair method:

Move the gear to the middle of the notch of the toothed rod sleeve, make the notch of the toothed rod sleeve face the rack, and then tighten the two stop screws on the end face of the tail guide rail with a small screwdriver. If it is invalid, it means that the rack is seriously worn, then it is necessary to remove the lens barrel. Screw out the upper and lower fixing screws of the rack, and use the rack upside down because the rack wears mainly in the upper part of the rack.


According to the rack’s width, cut a sheet of metal, so the sheet is embedded on the rack. And fix the sheet and rack on the lens tube with the fixing screw, then insert the lens tube for debugging. If you feel the tightness, you can change the thickness of the sheet until it is suitable. Or buy a new rack from the manufacturer according to the original model and specification.

2. The tube slides down by itself

The trouble is that when the focus is in focus, the lens barrel will slide down by itself when the focus screw is released by hand, resulting in inaccurate focus.

In the structure of microscope coarse adjustment, the tightness of the gear shaft is generally controlled by the friction between the gear rod sleeve and the coarse adjustment knob. The friction between the gear shaft and the gear rod sleeve is obtained by pressing the two coarse adjustment knobs connected with the gear shaft on the end face of the gear rod sleeve through two plastic washers. The tighter the rough adjusting screw or the end face of the gear rod sleeve is pressed, the greater the friction force will be. The reason for the self sliding of the lens barrel is that the friction between the gear shaft, and the gear rod sleeve is reduced due to the wear and deformation of the washer after long service life, and the torque generated by the friction between the gear shaft, and the gear rod sleeve cannot overcome the torque generated by the gravity of the lens barrel itself.

Repair method:

Hold one side of the coarse adjustment knob with both hands and tighten the coarse adjustment knob in a clockwise direction. If not, thicken the gasket. Insert the needle-nose pliers into the double eye nut on the end face of any coarse adjustment knob, screw it out, remove the coarse adjustment knob, take out the plastic washer, cut a washer with the same diameter with green shell paper or thin plastic sheet, clamp it between the original washer and the coarse adjustment knob, and then reassemble it. Suppose it is challenging to rotate the coarse adjustment knob. In that case, it means that the washer is too thick, so a thinner washer should be replaced, in short, to rotate the coarse adjustment knob. If there is a specific resistance to rotation, the tube is not easy to slide down.

3.The light collector cannot be positioned or block

There are two kinds of common light collectors: one is a disc or light bar, on which there are circular holes of different sizes. The light barrier is positioned by the positioning spring. The ball under the loading table stuck in the positioning hole of the disc. When the ball is lost, or the spring fails, the light column can not be positioned.


The repair method is to replace the ball or spring. Now some manufacturers have changed the positioning method relying on the spring, and ball to positioning method depending on the spring plate. This kind of structure is firmer and less likely to be damaged.


The other is the rainbow light column, composed of twelve arc-shaped thin steel sheets (i.e., shading sheet). As long as the handle on the sliding weight is moved, the size of the aperture can be changed at will.


The common fault is that the small steel column on the shading plate falls off, causing the handle to be stuck, and the aperture cannot be changed.


The repair method:

Uses a small screwdriver to loosen the two fixed screws on the light barrier. Please take out the light shield, reinstall the fallen off small copper column on the light protection, and glue the small copper column with 502 glue to prevent it from falling off again. When installing, pay attention to the opposite direction of the two small copper pillars on each light shield. Or find a small section of copper wire whose thickness is closely matched with the aperture of the light sheet to make a small copper column, and then put the bottom plate of the light barrier upward. Insert the small copper column at one end of each light shield into the small hole of the bottom plate, and arrange it piece by piece in the reverse direction. Then, the sliding groove on the sliding plate is successively covered on the small copper column at the other end of the light shield. The cover plate is covered, and the three fixing screws are tightened. Suppose one light shield is broken, as long as the broken one is taken out. The light barrier can still be used commonly. More than two broken ones should be purchased from the manufacturer for replacement.


4. The tilt joint is too loose

The tilt joint refers to the joint between the mirror arm and the column. When using the microscope, the mirror arm is often tilted back to an angle convenient for observation. After using, the tilt joint may become loose, resulting in the mirror arm being tilted at will.


The repair method:

It is to insert the pointed nose pliers into the two double eye nuts on the end face of the tilt joint and rotate clockwise until the mirror arm is tilted with proper tightness. If it is invalid, it may be that the friction washer on the two end faces of the mirror arm and the column is worn, so it is necessary to thicken the washer, screw off the double eye nut with the pointed nose pin, take out the rotating shaft, cut a figure with the same diameter with green shell paper or thin plastic sheet, thicken the original washer, and reassemble it.

5. The pin of the reflector is too loose or too tight in the socket

There are two common types of reflector pin structures

One is an open slot on the pin, depending on the width of the slot, to adjust the tightness of the pin in the socket. When the pin is too loose in the socket, a slotted screwdriver can be used to insert into the pin’s slot to enlarge the opening of the slot so that the tightness of the pin in the socket is appropriate. On the contrary, when the pin is too tight, the opening of the slot on the pin can be narrowed with wire pliers.


The other is to adjust the tightness of the pin in the socket by using the locking screw. When the pin is too loose in the socket, the locking screw can be tightened with a screwdriver. If the pin is too tight in the socket, it is easy to break the pin when the reflector is rotated. You can use a screwdriver to loosen the locking screw.

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