Troubleshooting common malfunctions in biological microscopes
1、 Troubleshooting common faults
1. The self sliding of the lens tube: This is one of the common malfunctions that occur in biological microscopes. The solution for the microscope with a sleeve structure can be divided into two steps.
Step 1: Hold the two coarse adjustment handwheels with both hands and tighten them with relative force. See if the problem can be solved. If it still cannot be solved, use a dedicated double column wrench to unscrew a rough adjustment handwheel and add a friction plate. After tightening the handwheel, if the rotation is difficult, the added friction plate is too thick and can be replaced with a thin one. It is based on the effortless rotation of the handwheel, easy movement of the lens tube up and down, and without self sliding. Friction plates can be made from waste photographic film and soft plastic sheets less than 1 millimeter thick using a punch.
Step 2: Check the meshing status between the gear on the rough adjustment handwheel shaft and the gear rack on the mirror tube body. The upward and downward movement of the mirror tube is completed by the gear driving the rack. In theory, the optimal meshing state between gears and racks is that the indexing line of the rack is tangent to the indexing circle of the gear. In this state, the gear rotates easily and has minimal wear on the rack? There is a wrong approach now, which is to add shims behind the rack to tightly press the gear to prevent the mirror tube from sliding down. At this point, the indexing line of the rack intersects with the indexing circle of the gear, and the tooth tips of the gear and rack tightly support each other's tooth roots. When the gears rotate, severe grinding occurs between them. Due to the fact that the rack is made of copper material, the gear is made of steel material. So mutual grinding will damage the teeth on the gear rack, and a lot of copper shavings will be generated on the gear and gear rack. Finally, the rack will be severely worn and unusable. Therefore, it is important not to use a raised rack to prevent the lens tube from sliding down. The solution to the problem of the mirror tube slipping by itself can only be achieved by increasing the friction force between the rough adjustment handwheel and the eccentric shaft sleeve. But there is an exception, which is that the indexing line of the rack is separated from the indexing circle of the gear. When turning the coarse adjustment handwheel at this time, there will also be a phenomenon of idle slipping, which affects the up and down movement of the mirror tube. If this is achieved by adjusting the eccentric shaft sleeve of the rough adjustment handwheel, the meshing distance between the gear and the rack cannot be adjusted. It can only be solved by adding appropriate thin sheets behind the rack. The standard for adjusting the meshing distance between the gear and rack with shims is that it is not difficult to rotate the coarse adjusting handwheel, but it also does not idle.
After adjusting the distance, add some neutral lubricating grease between the gear and rack. Just move the mirror tube up and down a few times* Afterwards, it is necessary to tighten the two compression screws on the eccentric shaft sleeve. Otherwise, when turning the coarse adjustment handwheel, the eccentric shaft sleeve may rotate along with it, causing the gear rack to become stuck and preventing the mirror from moving up and down. If the force of turning the rough adjustment handwheel is too large at this time, it may damage the gear rack and eccentric shaft sleeve. If it is found that the eccentric shaft sleeve still rotates after tightening the compression screw. This is caused by the screw hole thread of the compression screw not being properly adjusted. Because manufacturers use machines to modify threads, there are often one to two threads that have not been properly modified. At this point, even if the screws are tightened, the eccentric shaft sleeve cannot be tightened properly. To discover this fault, simply use an M3 tap to thread through the screw hole and solve the problem. I have thoroughly solved the problem of eccentric shaft sleeves following rotation for 30 biological microscopes in our school using this method.
After completing all these steps one by one, the problem of the mirror tube sliding down on its own has basically been completely solved.
2. Defective positioning of the sunshade: This may be due to the loose fixing screws of the sunshade, causing the positioning marble to escape from the positioning hole. Just put the marble back into the positioning hole and tighten the fixing screw. If it is difficult for the sunshade to rotate after tightening, a washer needs to be added between the sunshade and the loading platform. After the thickness of the washer is tightened with screws, the sunshade rotates easily, and the positioning marble does not escape. Correct positioning of the sunshade is preferred.
3. Difficulty in rotating or positioning the objective lens converter: The difficulty in rotating the converter may be due to the tightening of the fixing screws. Make it difficult to rotate and damage the parts. If it is too loose, the bearing beads inside will detach from the track and squeeze together, making it difficult to rotate; Additionally, the marble is likely to come out, with a diameter of only one millimeter, making it easy to lose. The tightness of the fixing screws is based on the ease and freedom of the converter during rotation, with no loose clearance in the vertical direction. After adjusting the fixing screws, the locking screws should be immediately locked. Otherwise, after the converter rotates, problems will occur again.
4. Eyepiece and objective lenses are contaminated or moldy: Most microscopes will experience contamination or mold on the outside of the lenses after a period of use. Especially for the high-power objective 40X, when conducting the experiment of "Observing the Separation and Restoration of Plant Cell Plasmal Walls", it is extremely easy to be contaminated by sugar solution. If the lens is contaminated and not cleaned in a timely manner, mold will occur. The treatment method is to first use a clean and soft silk cloth dipped in warm water to remove pollutants such as sugar solution, then dry it with a dry silk cloth, then use a long fiber degreased cotton dipped in lens cleaning solution to clean, and then use a hair dryer to blow dry. It should be noted that the cleaning solution must not penetrate into the interior of the objective lens. Because in order to achieve the required magnification, the lenses of high-power lenses need to be tightly glued together. Is the adhesive transparent and very aggressive? Once this layer of adhesive is dissolved by solvents such as alcohol and ether, the light path will change when it passes through these two lenses. The observation effect will be greatly affected. So during cleaning, do not allow solvents such as alcohol and ether to penetrate into the interior of the objective lens.?
5. When the mirror frame and mirror buttocks tilt, they cannot be fixed: this is caused by the loose connection screws between the mirror frame and the base. You can use a dedicated double headed wrench or use a pointed pliers to clamp the two eyelets of the double eye nut and tighten them firmly. If the problem cannot be solved after tightening, appropriate gaskets need to be added to the nut to solve it.
If the lenses inside the eyepiece or objective lens are contaminated or moldy, they must be disassembled and cleaned. The eyepiece can be directly unscrewed and removed for cleaning. But the structure of the objective lens is relatively complex, with very strict requirements for the stacking of lenses and the distance between each lens, and high accuracy. The manufacturer is calibrated and positioned during assembly. So after disassembling and cleaning, it is necessary to strictly assemble it as it is.
