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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Repair of LPM imported radio tape recorders. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Ham Radio Technologies

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With all the variety of models of tape recorders sold on the market, almost all, mainly manufactured in Asia, have the same or very similar CVLs. Moreover, they differ in very mediocre quality. If at first the mechanism seems to work well, then after two to three hundred hours of operation of the tape recorder in playback mode, clicks are already heard, gradually turning into crackling, the winding starts to work intermittently, jamming the tape.

This defect is the result of wear of the drive plastic gear of the winding and rewinding unit, or rather its small stage, at the point of engagement with the intermediate winding gear. In most CVLs, it has been observed that the engagement occurs at the very edge of the drive gear ring gear, which heavily stresses the material and leads to premature wear. The rest of the teeth (about 2 mm) remain intact.

To eliminate the defect, it is enough to lift the drive gear, while the clutch will move to an undamaged area. To do this, it is necessary to remove the winding and rewinding unit with a plastic lever, having previously removed the belt from the pulley, disconnected the spring and unscrewed the fixing screw. In some models, there is no screw - the entire assembly is fixed to the panel with a plastic latch. If you carefully pry it off with a screwdriver from the side where the cassette is located, the assembly can be easily removed. Having removed the gear from the axle, a washer 0,25 ... 0,35 mm thick is placed under it, so that after assembly the gear engages with an undamaged area. As a result, the normal operation of the LPM is most often restored.

In my opinion, the rapid wear of the teeth is caused by an excessively large winding force, which is observed in almost all "Asian" radio tape recorders. You can try to reduce it in this way: holding the gear of the receiving unit with your fingers, slightly turn and pull up the boss of the cassette - it should rise slightly. If this does not give the desired effect, the boss must be removed from the axis; it is fixed with a plastic washer, removed with a sharp needle. Then take out the spring and shorten it by about 0,5-1 turn. After assembly, the winding may be weak. Then the spring is slightly stretched, thus selecting the optimal winding force.

Author: S. Ovsyannikov, Orenburg region

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