Sharp CE-52 tape recorder repair.
OneFault phenomenon
According to the seller's description, the external power adapter is connected, and the machine does not respond.
After buying it, install the battery, press the playback button, tape, and the speaker has no sound. According to the fault phenomenon, the preliminary judgment may be that the circuit is faulty or the speaker is damaged.
2. Fault finding
Open the case, expose the circuit board, press the playback button, smell the odor, immediately press the stop button, and observe the recording and playback integrated core UPC1350G
Figure 1
There are burn marks around the third foot (see Figure 1), and the manifold is severely heated when touched with your hand. In this case, it cannot be powered on again so as not to expand the scope of the fault. Measure the speaker with the MF47 multimeter R 1, and the speaker makes a clicking sound, indicating that the speaker is normal. Use the MF47 multimeter resistance R 1K gear pin, exchange the meter pen and measure again, it is about 70 ohms, so it is suspected that the integrated block is burned. Remove it and measure it again, which is basically the same as ** measurement. Buy a new manifold, use MF47 multimeter resistance R 1K gear pin resistance about 7K, exchange the meter pen to measure about 15K again, measure the resistance between the pins 200, and exchange the meter pen.
Three, reasonAnalytics
After consulting the information, the Sharp CE-52 tape recorder comes with an external power adapter DC direct plug male socket metal inner pin is the negative pole, and the inner wall of the DC head is the positive pole, which is just the opposite of the current domestic power adapter DC direct plug male metal inner pin and inner wall polarity. So after the seller plugged in the machine, the manifold burned due to the opposite polarity of the power supply.
Four, repairs
Replace with a new UPC1350G manifold and the machine will return to normal. In the test machine, it was found that sometimes when the ** button was pressed, the machine had a clicking sound, and the ** key was not pressed in place. Suspecting that the reset of the self-stop mechanism was not complete, I opened the reverse side of the movement and found that the self-stop paddle was always unable to retreat in place (see Figure 2). Began to suspect the reason for the relaxation of the return spring of the lock key plate, and the fault was still the same after cutting, and after analysis, it was found that the torsion spring of the automatic paddle was separated from the torsion spring groove, resulting in the paddle back not in place, and the torsion spring was adjusted to the torsion spring groove of the self-stop paddle, and then the playback key was pressed, and the fault did not appear again.
Figure 2
February 17, 2024.