Service manual

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READ SECTION

2-C-5

2 UNIT EXPLANATION

[5] Original Read Control

Original read control is performed by the ADB (A/D

converter board) and CCD sensor installed in the ADB.

1. Operation

The light reflected by the exposed original is

input to the CCD sensor through the lens. The

analog voltage corresponding to the quantity of

input light is A/D-converted in the ADB, being

output to the ICB (image control board).

a. Original read

The original read timing is as follows:

(1) Platen mode

Specified interval after exposure unit turns PS6

(original HP) ON.

(2) DF mode

After lapse of the specified time after the origi-

nal’s leading edge turns ON PS308 (Original

conveyance).

[6] APS Control

The APS method used in the platen mode is different

from that used in the DF mode.

The signal read by the APS sensor or the original size

detection sensor of the RADF is processed by the ICB

(image control board).

1. Operation

a. APS detection

(1) DF mode

The original size is detected according to the

combination of ON/OFF states of PS302 (origi-

nal size detection 1) and PS303 (original size

detection 2) and the resistance value of VR301

(original size detection).

ICB IFB ICB

CCD

ADB

5VDC

PS62

SGND

PS63

PS64

PS65

PS66

PS67

PS68

PRCB ICB IFB