Samsung MAX-870, Service Manual

Page: 21 / 92

Special Circuit Descriptions
5-2 Samsung Electronics
5-1-3 Tracking Error Amp
5-1-4 Focus OK Circuit
The current signals from the side spot photo diode (E and F) are input to the E and F pin and converted into
voltage signals by E I-V and F I-V AMP. The output of tracking error amp is due to the difference between
E I-V AMP voltage output.
The E-F balance can be adjusted by modifying the gain of E I-V AMP, and the tracking gain(Pin TE1) can be
adjusted automatically by micom program.
Extracting the DC part of RFI and RFO and comparing with the basic DC level, if RF Level is more than basic
level, the FOK is output. The focus OK circuit generates a timing window of focus on to monitor the focus
search status of focus serve.
+
-
79
68
67
F
E
EI
TGFI
BAL< 4 0 >
GAIN< 3 : 0 >
from Digital
TGL
TGH
TE1
LPFT
BALL
To ISTAT,TRCNT
BALH
GAIN-UP/DOWN
75K
220K 110K
56K 27K 13K
13K
16K
7.5K 3.3K 1.5K
IV AMP
IV AMP
WIN COMP
WIN COMP
54 55
-
40K
40K
40K
90K
57K
FOK
VC+0.625V
+
- 74
75 40
+
-