Power Circuit In The Main Circuit - Sharp SF-2052 Serviceanleitung

(7) Memory (IC6, IC5)
The this model employs the EEPROM and the SRAM as its memory.
However, the this model has backup memory of IC6 AT28C64B
(EEPROM) only.
The EEPROM is a memory which keeps the data even when the
power is turned off. The EEPROM has the following two features:
1
The number of writing is limited (about 100K). (For the SRAM,
there is no limitation.)
2
It takes some time to write. (About 10 msec for 64 byte write. The
SRAM takes only 1 usec.)
Therefore, an access is made to the EEPROM as required.
•
When turning on the power:
The contents of the counter and the simulation are written from the
EEPROM to the SRAM.
•
During the power on:
Only the simulation data are written into the EEPROM.
•
When turning off the power:
Only the counter data are written from the SRAM to the EEPROM.

(8) Power circuit in the main circuit

In the this model main PWB, the 24V power voltage is supplied from
the DC power circuit, and IC18 (78M10H), IC52 (7824AHF) and IC17
(78M05H) generate the power used in the main circuit. This prevents
against abnormal operations of the main circuit due to the power line
noises.
DC power circuit Main circuit
IC18
+24V
FW
+38V IC52
(9) Auto exposure sensor (AES) and optical
system dirt sensor (AEDS) circuit
The auto exposure sensor (AE) and the optical system dirt sensor
(AEDS) circuit are composed of the sensor input circuit and the sen-
sor gain level select circuit.
When simulation No./ 47 is performed, the auto exposure sensor (AE)
reads the white paper level to determine the gain level. When simula-
tion no. 46 is performed, the optical system dirt sensor (AEDS) radi-
ates the reference plate on the back surface of the glass holder with a
constant light intensity (CL voltage: 70V) to determine the gain level.
AES
(AEDS)
IC122
AEGIN2
AEGIN1
AEGIN0
I/O
+10V(B)
RAM
CPU
IC17
+5V(C)
RO M
I/O
EE-PROM
+27V
+
-
IC116
Analog input
AES
(AEDS)
(10) Process control sensor (PCS, DNS) circuit
The process control sensor circuit is composed of the sensor input
circuit and the sensor gain level select circuit.
The process control sensor (PCS) and the drum mark sensor (DMS)
are divided into the light emitting section and the light receiving sec-
tion. The gain level in the light emitting section is controlled to obtain
a constant input voltage in the light receiving section. The input circuit
is provided with a variable resistor to adjust variations in the sensor
sensitivity with simulation No. 44-2, 3.
IC107
I/O
(11) Fan motor control circuit
The fan motor control is classified into two categories as follows:
1
ON during copying only
Optical system fan motor (CFM1, CFM2, VFM)
2
ON regardless of copying or standby
Fuser blower fan motor (VFM1)
To suppress noises in the standby state, selection of +24V/+10V is
performed.
VFM2a VFM1 VFM2b
1 1
1 1
1 0
1 0
0 1
0 1
0 0
0 0
ON
POWER
ON
+24V
+10V
VFM1 OFF
ON
+24V
+10V
VFM2
OFF
VFM3
1
1
Delay from POWER ON (about 100 msec)
Driven with +24V (for about 1.0 sec) →
2
4
During copying
Door open, JAM →
5
3
.)
12 – 8
+10V
PCS
(DMS)
VFM1 VFM2, 3, 4
OFF OFF
0
1 OFF +10V ON
0 +10V ON OFF
1 +10V ON +10V ON
0 +24V ON +24V ON
1 +24V ON +24V ON
0 +24V ON +24V ON
1 +24V ON +24V ON
ON
ON
2 3 4
3
Warmup, ready wait
6
Door close (Same process of
IC116
+ Analog
-
input
PCS
(DMS)
Power OFF,
door open,
trouble, JAM
NC
NC
Ready standby
Copying
NC
NC
NC
("1": "H", "0": "L")
OFF
OFF
5 6
→
1→ 2