Pioneer DEH-M8047ZT/UC Service Manual page 97

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1.3.5 RF level auto-adjustment (RFAGC)

This adjustment minimizes the dispersion of the RF level (RFO), which may be caused by disc-related errors, for more

stable signal transmission by changing the amp gain between RFI and RFO.

1) The microcomputer sends the command to the servo LSI to read out the output from the RF level detecting circuit

inside the servo LSI.

2) The microcomputer calculates the appropriate amp gain by using the output read out to adjust the RFO level at the

prescribed one.

3) The microcomputer sends the command to the servo LSI to adjust the amp gain into the calculated one.

This adjustment is automatically performed when:

1) During the setting-up mode, only the focus close operation ends.

2) Immediately before the setting-up ends (or right before the play mode starts)

3) During the play mode, the focus loop is locked again after unlocked.

1.3.6 Preamplifier gain adjustment

In this adjustment, when the reflected beams from disc surface are extremely weak (ex. when the lens is dirty, and a

CD-RW is loaded), the whole gain in the RFAMP block (FE, TE, and RF amplifiers) is increased by +6dB or +12dB.

When the system senses that the reflected beams from disc surface are extremely weak during the setting-up mode,

the whole RFAMP gain is increased by +6dB or +12dB.

After the gain is changed, the setting-up mode is restarted.

If the whole RFAMP gain is always increased to the +6dB level in the play mode, the +6dB level will be employed at the

starting of the setting-up mode from the next playback.

Gain of entire RFAMP

+ 12dB

+ 6dB

TYP

Fig.1.3.1 Pre-amp gain adjustment

Play the CD-RW with the gain being set to +12dB

y y y y y y y

Play at +6dB increases due to stained lens or other reasons

(the typical gain is employed for the initial setup)

Play is started with +6dB

judging the lens is stained

CX-3057

Time

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