Common troubleshooting of microscopes

The self sliding of the lens tube
This is one of the common malfunctions 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 a thin one can be replaced. Based on the effortless rotation of the handwheel, the mirror tube can move up and down easily without sliding down on its own. Friction plates can be punched with a punch using waste photographic film and soft plastic sheets less than 1 millimeter thick.
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 up and down 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 gears rotate easily and wear the racks the most? There is a wrong approach, which is to add a gasket 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 are tightly pressed against 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 and the gear is made of steel material. So mutual grinding will damage the teeth on the rack, and a lot of copper shavings will be produced on the gears and racks. Finally, the rack will wear severely and become unusable. Therefore, it is essential not to use a raised rack to prevent the lens from sliding down. To solve the problem of the mirror tube sliding down on its own, it can only be achieved by increasing the friction 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 slipping due to idling, 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, it is not possible to adjust the meshing distance between the gear and the rack. Only an appropriate thin plate can be added behind the rack to solve the problem. The standard for adjusting the meshing distance between the gear and the rack with shims is that it is not difficult to rotate the rough adjustment handwheel, but it also does not idle.
After adjusting the distance, add some neutral lubricating grease between the gear and the rack. Just move the mirror tube up and down a few times. Finally, 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 jam and preventing the mirror from moving up and down. If the force of turning the rough adjustment handwheel is too strong at this time, it may damage the rack and eccentric shaft sleeve. If it is found that the eccentric shaft sleeve continues to rotate after tightening the compression screw. This is due to the screw hole thread of the clamping screw not being properly modified. Because manufacturers modify threads using machines, 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 detect this fault, simply use an M3 tap to thread through the screw hole and solve the problem.
After completing all these steps one by one, the problem of the mirror tube sliding down on its own will be solved.
2. Defective positioning of the sunshade
This may be due to the fixing screws of the sunshade being too loose, causing the positioning ball to escape from the positioning hole. Just put the marbles back into the positioning holes and tighten the fixing screws. If it is difficult to rotate the sunshade after tightening, a washer needs to be added between the sunshade and the loading platform. After tightening the thickness of the washer with screws, the sunshade can rotate easily, and the positioning ball will not escape. It is best for the sunshade to be positioned correctly.