SHARP SP1666 Technical Report

Date: Jan. 21, 1994

COPIER : Z-88

No. : SP-1666

PREVENTION OF Q1 (FET ) DAMAGE CAUSED W HEN
THE PAPER FEEDER ROLLER LOCKS.

1.Model name: Z-88 / SF-2010

2.General: The Q1 (FET) of the main circuit board is sometimes damaged by paper feed roller A

when it locks. To prevent this damage from occurring, mylar has been added to the
paper feed roller A section. To further increase efficiency, the software has also been
changed to alleviate the problem when the paper feed roller A locks, before the Q1
damage actually occurs.

3.Reason: When a paper jam occurs for some reason during copy paper cassette feeding, the
jammed paper should be removed. When it is not removed, and instead the print button
is depressed and the copy function repeatedly employed, the jammed copy paper can
get caught and wrapped around paper feed roller A, causing it to lock up. When this
happens, an excessive electrical current (power surge) is created, causing the Q1
(FET) damage mentioned above.
Also, when a volume of copy paper greater than the specified limit is loaded in the copy
paper cassette (280 sheets or more for a cassette built to hold 250), paper feed roller A
can lock up, placing a burden on the main motor. This creates the above mentioned
power surge to Q1, causing the damage.

4.Description: Mylar is added to the area surrounding paper feed roller A, preventing the copy paper to
wrap around the paper feed roller.

Mylar (PSHEP3628FCZZ) added to pap feed roller A.

Front.

Standard
plane.

Standard
plane.

Back.

Paper feed roller A.

Standard
plane.

Paper feed roller A.

Paper feed roller A mylar.

Taped area.
Mylar area.

SHARP CORPORATION Reprography Division

1/3

Green

C

* Caution: When exchanging paper feed roller A, it is necessary to remove the paper

feed roller mylar.
After exchanging paper feed roller A, 2 sheets of mylar must absolutely be
attached.
The mylar should be attached so that it does not touch paper feed roller A.

• To increase efficiency, the software has been changed so that the revolutions of the

paper feed roller are checked by an encoder. 200 msec after paper feed roller A locks
up, “P” is displayed. If the print button is pressed and the copy function employed while
in this state, the locked condition is checked and “L4” is displayed within 200 msec.

CPU VHI78011GC526 → VHI78011GC537
Main circuit board CPWBS0955FC58 → CPWBS0955FC59

5.Action: (Factory action)

Addition of paper feed roller A mylar : From November, 1993. (Include SMF)
Software change : From 1993 mid-November. (Include SMF)

(Field action)

When the problem described above actually occurs in the market, it should be handled
by adding the paper feed roller mylar and exchanging Q1.

Current New

* The paper feed roller can sometimes lock up when loading the copy paper cassette

with a volume of copy paper exceeding the l imi t (250 sheets). To prevent this problem
from occurring, the users should be instructed to not load the copy paper cassette more
than the limit displayed on the paper cassette.

The limit.

2/3