Led Eraser Array - Toshiba 1550 Service Manual

9.5 LED Eraser Array

Brief description
• LED eraser array:
a) For reduction copying, the areas on the
drum where the light from the exposure
lamp does not fall are exposed.
b) Exposes the portion, which is out of the
paper size and unnecessary charged, ac-
cording to the cassette size signal.
The LEDs are turned on and the drum surface
is irradiated the charge in the area hit by the
light disappears from the drum surface
image of the section where the light has fallen
is therefore erased.
Operation description
• The LED eraser array consists of 32 LEDs, and the LEDs are in the same position in the front/rear
direction based on the image center, are connected to the same bit in parallel.
• Data (according to input coordinate for paper size, reproduction rate) from the logic PC board are fed
to LED eraser array by 64 bits (effective data are the last 16 bits).
Data "1": LED ON, Data "0": OFF (the level on the input pins of IC L7932 of the driver controller)
Ex.) When one LED is turned ON at both ends of LED array:
• "1" is fed from logic PC board to the 64th (last) datum (16th effective datum), and "0" to data 1 – 63
(effective data 1 – 15).
• "1" is set in shift register equivalent to ED1 and ED32, and "0" is set for the others.
• After setting is completed, it is transferred to latch.
• According to the driver, turn ON LED on both ends in accordance with data.
A timing chart for the above is shown below.
Mar. 1998 © TOSHIBA
LED eraser array
Drum
the
9 - 11
Non-image section
Non-image section
1550/1560 DRUM