This fault is caused by the supply of the 8V regulator circuit of the decompression board (as shown in Figure 1) of the bridge rectifier diode 2D37~2D40 (1N4001) of the aging performance of the poor. 1N4001 reverse peak pressure (PIV) to 50V, rated current of 1.0A, after a few years of work can not meet the decompression plate current of power supply requirements, poor performance, resulting in the disc reading, voltage fluctuation is too big, has more than 1V (normal within a few tenths of a Funei fluctuations).S3Hservice manual download site
This failure is easily misdiagnosed as is decompression board thermal stability bad, because according to the sound figure interlocking principle and fault position should be in the decompression (CL484) or the CD board, and play a CD, most normal, sometimes silent. In the silent, the DATA output of the CD DSP and output to the audio DATA (as shown in Figure 2), then the sound of the speaker is more prone to the fault [location on the decompression board. Measuring decompression of the decompression in normal block CL484 power supply (112) foot 3.3V, the reset terminal (101) pin high normal level, for crystal oscillator is also invalid.S3Hservice manual download site
Check the machine decompression power supply circuit (Figure 1) by the output power transformer AC 9V voltage by 2D37, 2D38, 2D39, 2D40 bridge rectifier, filter C317, voltage of 10V, via 2BG46, 2BG47, 2BG43 and series voltage regulator, voltage 8V, supply decompression board of three terminal regulators block W1 (7805). 7805 the output of the +5V voltage by D6, D5 two diode buck, get 3. 3V voltage to CL484 power supply. Normal machine in VCD, into the disk, when read dish series voltage regulator tube 2BG47 (2SD313) output (emission) voltage fluctuation is very small (within a few tenths of a Funei fluctuations), and measured the machine read dish voltage 8V unexpectedly dropped to 6V, is very unstable. The replacement of 2BG46, 2BG47, 2BG43 and other components, the fault is still. Finally, pay attention to the original machine of bridge rectifier tube adopts the 1N4001, with the fault disappears after four BA159 substitution machine all the normal and error correction is used to have a greatly improved.

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