PIONEER DEX-MG4157ZT-91/UC
Service Manual

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6) RF level automatic adjustment (RFAGC)
This adjustment is performed in order to adjust variation of RF signal (RFO) level to fixed value and to realize reliable signal transmission. The adjustment is performed with changing amp gain between RFI and RFO. Adjustment steps (1) The microcomputer reads out output from RF level detect circuit inside servo LSI by a command. (2) The microcomputer calculates desired RFO level of amp gain volume from read value. (3) The microcomputer sends an appropriate command to servo LSI to reach to the gain volume of (2). This adjustment is performed at the following timing, � During set-up, only focus-close is finished � At the point of set-up completion (just before playing) � During playing, after recovering from out-of-focus 7) Adjustment of gain of preamp stage If there is lens dirt, or reflected light of a disc is notably small during CD-RW replaying, gain of entire RFAMP(FE, TE, RF amp) should be +6dB, +12dB according to the situation. Adjustment steps When reflected light of a disc is notably small during setup, the entire RFAMP should be +6dB, +12dB. In addition, when changing gain, perform again the set-up procedure from the start. When it is considered that "the entire gain of RFAMP is always played at +6dB", perform the set-up at +6dB in advance from the next time. See the figure below.
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B

Entire RFAMP GAIN Playing with +12dB gain with CD-RW, etc. + 12dB
C

+ 6dB
D

Detecting that "lens is dirty" and playing with +6dB from the start TYP

+6dB play increases because of dirt of lens, etc. (Set-up starts with TYP gain.)
Fig.14 Conceptual diagram of gain of preamp stage

Time

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F

CX-3168
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