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AR-285 (serv.man16)
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6
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Service Manual
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Device
Copying Equipment / AR280 285 335 Service Manual-Operational Description
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ar-285-sm16.pdf
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Sharp AR-285 (serv.man16) Service Manual ▷ View online

(5) Developing bias voltage correction
a. Outline and purpose
Deterioration of developer leads to changes in the environmental conditions.
To solve the above problem, the developing bias voltage is changed according to the situation to maintain the proper density print and prevent
against background copy. 
(Operation)
1) Three toner image patches are made on the OPC drum with the three voltages Vdbc and Vdbc 
±
 (n)a. (a = 50V)
2) Connect the three points of three toner patch density points with strait lines, and check that it reaches the reference density "38" (set with SIM
44-4).
If the above condition is satisfied, obtain the correction developing bias voltage (Vdbc(n)) for the reference density "38" by linear approximation. 
3) Calculate the developing bias correction voltage (
 Vdbc(n)).
The developing bias correction voltage (  Vdbc(n)) is applied to the developing bias voltage correction in all the operation modes. 
If the condition of 2) is not satisfied, change the condition of 1) as follows and make three toner image patches similarly to 1). 
(Contents of change)
Change the three developing bias voltages of correction for making toner image patches to Vdbc + (n 
±
 1) 
α
, Vdbc + (n 
±
 2) 
α
, and Vdbc + (n 
±
 3) 
α
, and execute 1) and 2). (
α
 = 50V)
Repeat the above operation until the condition of 2) is satisfied. (n = Number of toner patch forming. 3 toner image patches are made for once.)
The correction operation of the developing bias voltage should be in the range of 0 
 –750V. 
DEVELOPING BIAS VOLTAGE CORRECTION
Develping bias voltage
Reference level
(Set by T.C 44-4)
Limit(-750v)
800
Vdbc
Vdbc + (n)
α
Vdbc - (n)
α
Vdbc + (n+1)
α
Vdbc + (n+2)
α
Vdbc + (n+3)
α
60
Lower
50
40
38
Image patch density
30
20
10
Higher
0
100
200
300
400
500
600
700
∆  
Vdbc(n)
α
 = 50
PT2/BS2(1D1)2
PT3/BS3(1D2)3
PT2/BS2(1D1)2
PT3/BS3(1D1)3
 
∆  
Vdbc(n)
CASE 1
CASE 2
Vdbc(n)
Vdbc(n)
PT2/BS2(1D2)2
PT1/BS1(1D2)1
PT3/BS3(1D1)3
PT1/BS1(1D1)1
PT1/BS1(1D1)1
DEVELOPING BIAS VOLTAGE CORRECTION
Develping bias voltage
60
Lower
50
40
38
Image patch density
30
20
10
Higher
0
100
200
300
400
500
600
700
∆  
Vdbc(n)
PT1/BS1(1D1)1
PT3/BS3(1D1)3
PT1/BS1(1D1)1
PT2/BS2(1D1)2
PT3/BS3(1D1)3
∆  
Vdbc(n+1)
FIRST
SECOND
Vdbc(n)
Vdbc(n+1)
α
 = 50
Vdbc
Vdbc + (n)
α
Vdbc - (n)
α
Vdbc(n) - (n)
α
Vdbc(n)
Vdbc(n) + (n)
α
800
Reference level
(Set by T.C 44-4)
PT2/BS2(1D1)2
Limit(-750v)
12 – 3
(6) Main charger grid voltage correction 2
a. Outline and purpose
When the developing bias voltage is changed, the main charger grid voltage correction 2 is performed to maintain the relation between the
developing bias voltage and the main charger grid voltage at constant. 
b. Details
After the developing bias voltage correction, the voltage of correction of the developing bias voltage is automatically added to the main charger grid
voltage.
Actual main charger grid voltage variable range: –200 to –900V
(7) Laser beam power correction 2
To maintain the OPC drum bright potential at constant for changes in the main charger grid voltage due to main charger grid voltage correction 1
and 2, the laser beam power must be changed accordingly. 
Laser beam power correction 2 is performed to output the laser beam power according to the above situation. 
This correction provides stable print density. 
(8) Toner concentration correction 
a. Outline and purpose
This correction is used to correct changes in the developer characteristics due to aging and change in the environmental conditions. 
When any change occurs in the developer characteristics, it causes under-toner or over-toner, resulting in improper print density. 
To prevent against this, the reference toner control level is changed according to the conditions to maintain the specified toner concentration. 
This correction provides stable print density.
b. Details of operation 
When the developing bias correction voltage (  Vdbc(n)) is minus-corrected (shifted to the positive polarity direction), it is recognized as an
increase in developing capability, and the reference toner concentration control level set with SIM 25-2 is increased. 
With the above operation, toner concentration is decreased to maintain the proper print density. 
The correction data is cleared to "0" when SIM 25-2 is executed.
TONER CONCENTRATION CORRECTION
1
99
T(time)
MAX 20
5
Operated process(DV bias correction) correction
Toner concentration
control level
Original reference toner
concentration control 
level(Set by SIM25-2)
12 – 4
(6) Main charger grid voltage correction 2
a. Outline and purpose
When the developing bias voltage is changed, the main charger grid voltage correction 2 is performed to maintain the relation between the
developing bias voltage and the main charger grid voltage at constant. 
b. Details
After the developing bias voltage correction, the voltage of correction of the developing bias voltage is automatically added to the main charger grid
voltage.
Actual main charger grid voltage variable range: –200 to –900V
(7) Laser beam power correction 2
To maintain the OPC drum bright potential at constant for changes in the main charger grid voltage due to main charger grid voltage correction 1
and 2, the laser beam power must be changed accordingly. 
Laser beam power correction 2 is performed to output the laser beam power according to the above situation. 
This correction provides stable print density. 
(8) Toner concentration correction 
a. Outline and purpose
This correction is used to correct changes in the developer characteristics due to aging and change in the environmental conditions. 
When any change occurs in the developer characteristics, it causes under-toner or over-toner, resulting in improper print density. 
To prevent against this, the reference toner control level is changed according to the conditions to maintain the specified toner concentration. 
This correction provides stable print density.
b. Details of operation 
When the developing bias correction voltage (  Vdbc(n)) is minus-corrected (shifted to the positive polarity direction), it is recognized as an
increase in developing capability, and the reference toner concentration control level set with SIM 25-2 is increased. 
With the above operation, toner concentration is decreased to maintain the proper print density. 
The correction data is cleared to "0" when SIM 25-2 is executed.
TONER CONCENTRATION CORRECTION
1
99
T(time)
MAX 20
5
Operated process(DV bias correction) correction
Toner concentration
control level
Original reference toner
concentration control 
level(Set by SIM25-2)
12 – 4
(6) Main charger grid voltage correction 2
a. Outline and purpose
When the developing bias voltage is changed, the main charger grid voltage correction 2 is performed to maintain the relation between the
developing bias voltage and the main charger grid voltage at constant. 
b. Details
After the developing bias voltage correction, the voltage of correction of the developing bias voltage is automatically added to the main charger grid
voltage.
Actual main charger grid voltage variable range: –200 to –900V
(7) Laser beam power correction 2
To maintain the OPC drum bright potential at constant for changes in the main charger grid voltage due to main charger grid voltage correction 1
and 2, the laser beam power must be changed accordingly. 
Laser beam power correction 2 is performed to output the laser beam power according to the above situation. 
This correction provides stable print density. 
(8) Toner concentration correction 
a. Outline and purpose
This correction is used to correct changes in the developer characteristics due to aging and change in the environmental conditions. 
When any change occurs in the developer characteristics, it causes under-toner or over-toner, resulting in improper print density. 
To prevent against this, the reference toner control level is changed according to the conditions to maintain the specified toner concentration. 
This correction provides stable print density.
b. Details of operation 
When the developing bias correction voltage (  Vdbc(n)) is minus-corrected (shifted to the positive polarity direction), it is recognized as an
increase in developing capability, and the reference toner concentration control level set with SIM 25-2 is increased. 
With the above operation, toner concentration is decreased to maintain the proper print density. 
The correction data is cleared to "0" when SIM 25-2 is executed.
TONER CONCENTRATION CORRECTION
1
99
T(time)
MAX 20
5
Operated process(DV bias correction) correction
Toner concentration
control level
Original reference toner
concentration control 
level(Set by SIM25-2)
12 – 4
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