SHARP SP1885 Technical Report

Date: Jun. 19, 1995

COPIER : Z-20

No. : SP-1885

REGARDING COPIES WITH BLANK AREAS

1.Model name: Z-20/25/27

2.General: Under conditions of high humidity, the CRU unitUs internal MC Charger may cause a

situation where a charge cannot be created on the drum. This causes blank areas on
copies as illustrated below.

[Malfunctioning state] Blank areas show up on the copy.

Front

Halftone

A blank, white area remains.
The blank area is typically not in
a straight line, and has varying width.

3.Description: In order to stabilize the discharge from the MC unit, please carry out the following repair.

(1)Make the high-voltage flow to the main circuit higher, and increase the electric supply

to the charger. (turning the setting volume (VR 201) to the right increases the supply)

(2)Change the high voltage resistance for the copy unit and increase the flow of

electricity.

Increase the resistance from 510 KΩ to 1.5 MΩ

(Supplementary Explanation)

The high voltage circuitUs electric current is used partly for the belt charger and
partly for the copy unit charger. The resistance for the copy unit charger is used to
adjust the flow of electricity in both parts. Making the resistance for the copy unit
charger higher also increases the flow of electricity in the belt charger.

SHARP CORPORATION Reprography Division

1/4

Green

C

Electric flow output (Io)

Belt charger flow (Im)

Main PWB

board high voltage

Copy charger
flow (It)

Please carry out these repairs for any units produced after Mar., 1995 which
malfunction in the way described above.

4.Procedure: (1)Remove the copy unit

➀ Take off the four screws connecting the

rack cover and remove the rack cover.

Rack cover

Copy unit
resistance

Copy

unit

charger

Belt

charger

➁ Take off the rack gear bracket. (Make sure

to pull the screws out in the right direction)

➂ Slide the copy unit over and remove the 3 screws attached to the Accuride.
➃ Slide the copy unit sideways and off of the frame.

(2) Remove the top cabinet

➀ Open the front door and take out the development cartridge.
➁ Remove the five screws holding the top cabinet in place.
➂ Pull the top cabinet up and off.

Top cabinet

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Development cartridge