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Elimination of belt slippage in VCRs. Encyclopedia of radio electronics and electrical engineering. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Телевидение

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If problems arise with loading and unloading video cassettes in VCRs, the author of the article published below offers a simple repair method. To do this, he recommends treating the belts in the mechanism with a special compound.

In some videocassette recorders (VMs), after a relatively short period of operation, failures in the mechanism for loading and unloading video cassettes occur. The unloading command is carried out with a characteristic tearing sound from a running engine, and the cassette is either not unloaded or unloaded with difficulty after significant slipping. The reason is the slipping of the belts in the drive mechanism for the shaft loading of the cassette. Its simplified kinematic diagram is shown in the figure.

Elimination of belt slippage in VCRs

In such a common design, the force from the DC motor 1 is transmitted to the drive shaft 2 through two rubber belts 3, 4 and pulleys of different diameters. Pulleys are usually plastic. The adhesion of the surface of the belts to them is relatively small. At the same time, the required force, especially when unloading the cassette, must be significant. As a result, even with slight operational wear - stretching of the belts, smoothing their surface - slippage occurs on the pulleys. In this case, engine 1 runs idle until emergency (with slipping) unloading of the cassette or the VM is turned off by the protection system. Since the specified drive is also involved in other normal operating modes of the device, in parallel, failures may occur during rewinding, threading the tape, etc.

Well-known recommendations for wiping pulleys and belts with alcohol are useless in practice: it does not dissolve fat well and has a destructive effect on rubber. The radical way is to replace the belts. However, for this, firstly, you need to have a spare set of them for a specific model of the device, and secondly, it requires dismantling the cassette receiver and even the entire drive mechanism, which is easy to disassemble, but can be difficult to assemble. In any case, such painstaking work requires certain qualifications.

Another way to eliminate this problem is proposed. Its essence lies in the fact that the surface of the belts is covered with a special composition of Radical glue and rosin. The composition is prepared by thoroughly mixing a small amount of “Radical” glue (or another rubber-based one) and ground rosin “to dust” in a ratio of 1: 0,5...0,7 (by volume). If necessary, the mixture is slightly diluted with gasoline. Passengers 3 and 4 are removed from the pulleys (without disassembling the mechanism), pre-wiped with gasoline, then coated with the prepared composition. After it dries for XNUMX hours, a layer with high adhesion and an increased coefficient of friction (due to rosin) is formed on the working surface. Next, return the belts to their place. The performance of the VM is completely restored. Sometimes it is enough to perform this operation for only one slipping belt.

In the event that the drive mechanism is difficult to access even for removing the belts, they can be left in place. In this case, the coating operation is performed with a long thin brush, gradually pulling the belt along the pulley with tweezers. Spread with a liquid composition, it glides easily over the plastic surface. To prevent the belt from sticking to the pulleys, the cassette is periodically loaded and unloaded to “turn” the mechanism. This should be started immediately after the composition thickens (after 20...30 minutes).

The method is easy to implement due to the availability of components and is highly effective. The performance of the VM is restored for a long time. Theoretically, some uneven rotation is possible due to different thicknesses of the coating, but for the mechanism under consideration this does not matter. If the applied layer wears out over time, the operation can be easily repeated.

Author: A.Pakhomov, Zernograd, Rostov Region

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Comments on the article:

Vladimir Vladislavovich
Of course, you can use gasoline if you are 100% sure that the rubber is oil and petrol resistant, otherwise it will spill out, it’s better to just rub it with rosin.


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