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The machine uses Sony KSS - 213C laser head, RF amplification and digital signal processing circuit are respectively the cxa1821m and CXD2545Q, literally take out five on the other VCD machine can be played normally DVCD dish and a karaoke VCD disc in this machine probation OK. Results only a DVCD dish can read TOC, and unable to get into the state of play or once in a while to enter play state but the mosaic phenomenon is particularly serious, and VCD disc read dish and normal play. According to the experimental results. Analysis circuit parts of the machine failure is unlikely. The reason may be bald aging or spindle motor side resulting in playback standard disc DVCD non high density when cannot read disk of the phenomenon.7Ecservice manual download site
The dynamic voltage of the RF signal output end of the {16} signal output end of the VCD is lower (playing DVCD 2.97V), and the normal dynamic voltage should be around 3.5V, which indicates that the output of the RF signal is not caused by the optical aging. With the new SONY 213C - KSS with the replacement of the test machine with a bald head assembly, the results were unexpected, the failure phenomenon has not changed, still can not read DVCD disc. Then re measured foot the {16} cxa1821m VCD playback in dynamic voltage 3.62V, than old bald test machine to measure voltage value increased 0.65v and confirmed the bald does have different degrees of aging.
Why the failure of the replacement of the optical components after the failure has not improved? Is it a digital signal processing circuit or its power supply part of the problem caused by the demodulation circuit can not be a DVCD disk data to produce this strange fault? The estimate is that the power supply circuit or the RF signal is affected by the interference of the CXD2545Q in the data that can identify the VCD disk and the critical state of the DVCD disk data can not be identified. The inspection of the relevant circuit (see photo). The output voltage of three terminal voltage regulator is 5.05V normal, and the filter capacitor C129, C146, C171, C147, C128 are normal. To confirm the power of the CXD2545Q signal input terminal voltage {36} 2.58V RF normal. Does the RF signal is blocked from the {16} CXD2545Q to {36} CXA1821M the {36} pin is not fully delivered to the CXD2545Q? So in measured R12 as normal 100 ohm, welding C120 in digital form capacitance block measured its capacity for 276pF, should 1800pf, obvious loss of capacity, try a 2200pf capacitor replaced after the test machine, VCD disc read speed to the disc significantly faster and five DVCD disc can successfully read disc and playback, of which only a DVCD dish have factors of the disc itself is a mosaic (may), try the r103 (gain adjustment resistance) again and a 470K resistor test machine, the mosaic phenomenon disappeared. At this point the fault completely ruled out. After the exchange for the original machine head assembly, play disc DVCD still read dish is difficult, can occasionally read, when playing mosaic is particularly serious, try adjusting power of laser resistor trimming effect is not obvious, that bald has indeed aging, can not be reused.
Summary: This machine although the surface is a fault, but the damaged parts has two, one is laser heads ageing; second is to reduce the RF signal coupling capacitance and both of them are reading DVCD dish the causes leading to the fault, to maintenance judgment difficult.
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