Ricoh FW740 Service manual

IMPORTANT SAFETY NOTICES

PREVENTION OF PHYS ICAL INJURY

1. Before disassembling or asse mblin g pa rts of the copie r and perip herals,
make sure that the copier power cord is unplu gg ed.

2. The wall outlet should be near the copier an d easily accessible.

3. Note that some compo ne nt s of th e copier and the peripherals are
supplied with electrical voltage even if the main switch is turned off.

4. If any adjustment or operat ion check ha s to be made with exterior covers
off or open while the main switch is turned on, kee p ha nds away from
electrified or mechanically drive n comp on ents.

5. The inside and the met al pa rts of the fusin g un it be come extremely hot
while the copier is operat ing . Be careful to avoid touching those
components with your bare hands.

6. The copier is not attach ed to th e ta ble. Pushing the copier to o ha rd may
cause it to drop onto the floor. While moving the copier, push the table.

7. When the main switch is turned on, th e mach ine will suddenly start turnig
to perform the developer init ializa tion. Keep hands away from any
mechanical and electrical components du ring this period .

HEALTH SAFETY CONDITIONS

1. Never operate the copier without the ozone filters installed.

2. Always replace the ozone filters with the specified ones at the specifie d
intervals.

3. Toner and developer are non-to xic, bu t if you get eith er of them in your
eyes by accident, it may cause temp ora ry e ye disco mfo rt. Try to remove
with eye drops or flush with wat er as first aid. If un succe ssfu l, ge t med ical
attention.

OBSERVANCE OF ELECTRICAL SAFETY STANDARDS

1. The copier and its peripherals must be insta lled and maintained by a
customer service represen tative who has completed the training course
on those models.

2. Caution: The RAM pack on the main control board has a lithium battery
which can explode if replaced incorrectly. Replace the RAM pack only
with an identical one. The manufacturer recommends replacing the entire
RAM pack. Do not recharge or burn this battery. Used RAM packs must
be handled in accordance with local reg ulations.

SAFETY AND ECOLOGICAL NOTES FOR DISP OS AL

1. Do not incinerate the toner cartridge or the used toner. Toner dust may
ignite suddenly when exposed to open flame.

2. Dispose of used tone r, developer, and organic photoconductors
according to local regulations. (These are non-toxic supplies.)

3. Dispose of replaced parts in acco rda nce with local regulations.

4. When keeping used RAM p acks in order to dispose of them late r, do not
put more than 100 RAM packs per seale d box. Storing larger numbers or
not sealing them apart may lead to che mical rea ctions and heat build-up.

SECTION 1

OVERALL MACHINE INFORMATION

31 October 1994 SPECIFICATIONS

1. SPECIFICATIONS

Configuration: Table top
Copy Process: Electrostatic transfer system
Original Feed: Sheet feed
Original Size: Maximum: 914 x 2,000 (36" x 80")mm

Minimum: A4 (81/2" x 11") lengthwise
Copy Size: Same as "Original Size"
Copying Speed: 3 cpm (A1/D sideways)
First Copy: 24 seconds (A1/D sideways)
Warm-up Time: Within 5 minutes (Room temperature 23oC)
Multi-Copy: 1 to 1 only
Automatic Reset: 2 minutes after copyin g is finish ed (can be set

to 1, 3, 4, or 5 minutes or to no auto reset)
Photoconducto r: Organic photocond uctor drum
Drum Charge: Single-wire with grid plate (Negative Charge )
Reproduction Ratio: 1 : 1 (±0.5%)
Exposure System: Slit exposure via fiber optic arra y
Exposure Lamp: Fluorescent lamp (26 W)
Development: Dual-component dry toner system
Toner Replenishment: Cartridge system (750 g toner/ca rtridge)
Toner Consumption: 1,860 A1 or D copies per cartridge (6% origin al)
Development Bias: Negative
Toner Density Control: Direct toner density detection by induction

sensor
Image Density Adjustmen t: Development bias contro l + exposu re control
Paper Separation: Dual wire ac corona and pick-off pawls
Cleaning: Cleaning blade

1-1

SPECIFICATIONS 31 October 1994

Paper Feeding: Manual feed (roll feeder optional)
Image Fusing: Heat and pressure type, teflon (u pper) an d

silicone rubber (lower) rollers
Fusing Lamp: Nichrome wire lamp

(115 V: 1,100 W, 230 V: 1,100 W)
Self-diagnostic Codes: 11 codes, displa yed in copy counter

Power Source: 115 V/60 Hz....15 A

220 V/50 Hz....7 A

230 V/50Hz.....7 A

240 V/50 Hz....7 A

Power Consumption: Maximum: 1.4 kW

Warm-up: 1.2 kW

Ready: 0. 04 t o 1. 2 k W

Copy cycle: 1.3 kW
Dimensions (W x D x H): 1,080 x 570 x 490 mm

42.1" x 22.2" x 19.1"
Weight: 76 kg, 167.4 lb
Optional Equipment and Machine Configu rat ion

Configuration

Main frame Optional equipment

Roll feeder (A571) Table (A714)

A163 copier

Roll cutting rail (A570) –
Side guides (A569) –

Other Optional Equ ipment

• Paper Spool

• Drum anti-condensation heater

Specifications are subje ct to change witho ut notice.

Additional equipment

1-2

31 October 1994 PAPER PATH

2. PAPER PATH

D

E

A

B

C

A: Original Path
B: Paper from the manual feed
C: Paper from the roller feed
D: Paper exit
E: Original Path from Rear Feeder

1-3

6

8

DRUM PROCESSES 31 October 1994

3. DRUM PROCESSES

2

1

7

3

4

5

1. Charge

In the dark the charge coro na unit app lies a ne gative charge to the drum.
The grid plate ensures the charg e is app lied unif ormly. The charge remains
on the surface of the drum because the photo con du ctive drum has a high
electrical resistance in the dark.

2. Exposure

High intensity light from a fluo rescent lamp is reflected from the mo ving
original through the fiber optic array. The cha rge on the drum surface is
dissipated in direct proportio n to the inte nsit y of th e ref lect ed light , th us
producing an electric latent image on the drum surfa ce.

1-4

31 October 1994 DRUM PROCESSES

3. Development

The magnetic developer brush on th e development roller comes in contact
with the latent image on the drum surface . Toner particles are
electrostatically attracted to the negatively charged latent imag e are as.

4. Pre-Transfer Lamp

The pre-transfer lamp (PTL) illumin ates th e drum prior to image tran sfe r. This
reduces the attraction between the toner and th e drum, thus making image
transfer easier.

5. Image Transfer

Copy paper is fed to the drum surf ace , at the exact timing, to align the copy
paper and the develope d image on the drum surface. Then a stro ng negat ive
charge is applied to the back side of the paper. The negat ive charge pulls
the toner particles from the drum surface onto the paper.

6. Paper Separation

A strong ac corona discharge is applied to the back side of the copy pap er,
reducing the charge on the pap er an d breaking the electrosta tic at traction
between the paper a nd the drum. Then , th e stiffness of the copy paper
causes it to separate from the dru m. The pick-off pawls help to separate
paper which has low stiffness.

7. Cleaning

The cleaning blade, which is angled against drum rota tion (counter blade
system), removes any toner remaining on the drum surf ace.

8. Quenching

The light from the quenching lamp electrically neutralizes the surface of the
drum.

1-5

4

3

MECHANICAL COMPONENT LAYOUT 31 October 1994

4. MECHANICAL COMPONENT LAYOUT

21

20

19
18

17

16

15

14

22 23

24

25

1

2

5
6
7

8

9

10

11

13

12

1-6

31 October 1994 MECHANICAL COMPONENT LAYOUT

1. 1st Original Feed Roller

2. 1st Press Rollers

3. Copy Tray

4. Exit Rollers

5. Fusing Exit Rollers

6. Hot Roller

7. Pressure Roller

8. Gas Spring

9. OPC Drum

10. T/S Corona Unit

11. Main Drive Unit

12. Table

13. Paper Spool

14. Roll Feeder

15. Paper Registration Rollers

16. Development Unit

17. Toner Cartridge

18. Manual Feed Table

19. Charge Corona Unit

20. 2nd Original Feed Roller

21. Original Table

22. 2nd Press Rollers

23. Exposure Lamp

24. Fiber Optic Array

25. Cleaning Blade

1-7

DRIVE LAYOUT 31 October 1994

5. DRIVE LAYOUT

10

13

1211

15

16

1

2

3

14

4

5

6

9

8

7

1. Original Feed Roller Pulley

2. Original Feed Roller One Way Pully

3. Development Unit

4. Development Unit Relay Gear

5. Development Drive Chain

6. Paper Registration Roller Clutch

7. Drum Drive Relay Gear

8. Main Motor

9. Fusing Drive Chain

10. Exit Unit Drive Belt

11. Hot Roller Drive Gear

12. Fusing Drive Sprocket/Gear

13. Toner Collection Coil Drive Gear

14. Drum Drive Gear

15. Original Feed Drive Pulley

16. Original Feed Drive Belt

1-8

31 October 1994 ELECTRICAL COMPONENT DESCRIPTIONS

6. ELECTRICAL COMPONENT DESCRIPTIONS

Refer to the electrical compone nt layou t on the reverse side of the Poin t to
Point (Water proof paper) ind ex nu mbe rs.

Name Function Index. No.

Motors

Main Drives all mechanical components except the

fans. (DC Motor)

Exhaust Fan Removes the ozone built up around the drum

section to the ozone filter. (DC Motor)

Magnetic Clutches

Registration Drives the registration rollers. 30
Toner Supply Turns on to supply toner to th e de velo pment

unit.

Solenoids

Pick-off Pawl Moves the pick-off pawls again st th e dru m. 6

Switches

Main Supplies power to the copier. 17
Original &

Paper Feed
Safety

Cuts ac power when the original or pap er fe ed
unit is opened. 18

32

5

31

Fusing Exit
Safety

Sensors

Door Open Indicates "Door Open" in the operation panel

Toner Density Detects the density of toner in the deve loper. 26
Original

Registration
Light Detects the intensity of the exposure lamp

Entrance Feed Detects when copy paper is inserted (jam

Cuts ac power when the fusing exit unit is
opened.

and prohibits the key operation.

Detects when the orig inal lead edge passes at
the front of the exposure glass.

output.

detector).

1-9

12

29

4

27

24

ELECTRICAL COMPONENT DESCRIPTIONS 31 October 1994

Name Function Index. No.

Registration Detects when copy paper arrives at the

registration rollers (jam detecto r).

25

Exit Detects jams through the fusing exit unit. 7

Printed Circuit Boards

Main Controls all copier functions both dire ctly and

through other PCBs.

22

PSU Converts the ac voltage to dc voltage. 21
AC Drive Provides ac power to the fusing lamp and

PSU.

15

FL Regulator Stabilizes power to the exposure lamp. 23
Operation Panel Control the operatio n pane l displa y. 10

Lamps

Exposure Provides light to reflect the original’s image

onto the drum (fluorescent lamp).

2

Fusing Provides heat to the fusing unit. 3
Pre-Transfer

(PTL)

Reduces the charge on th e drum surface prior
to image transfer.

20

Quenching (QL) Neutralizes any charge remaining on the drum

surface after cleaning.

Power Packs

Charge/Bias/Grid
Power Pack

Transfer/
Separation

Provides high voltage power for the charg e
corona, charge grid, an d de velopment bias.

Provides high voltage power for the tran sfe r
corona and separa tion.

19

16

Thermistors

Hot Roller Monitors the hot roller’s surfa ce tempe rature. 8
Pressure Roller Monitors the pressure roller’s surface

temperature.

11

Thermofuses

1

Fusing Protects against fusing overheat. 9

1-10

31 October 1994 ELECTRICAL COMPONENT DESCRIPTIONS

Name Function Index. No.

Heaters

AnticondensationKeeps moisture from forming inside the copie r

(option).

Others

Total Counter Keeps track o f th e total length of copies made

(Europe) or the total copies made (U.S.A.).

Circuit Breaker
(Europe, Asia)/

Guards against voltage surges in the input
power. 14

Fuse (U.S.A.)

13

28

1-11

SECTION 2

DETAILED SECTION

DESCRIPTIONS

31 October 1994 DRUM

1. DRUM

1.1 DRUM CHARACTERISTICS

The organic photoconductor (OPC) dru m has th e followin g cha ract erist ics:

• It is able to accept a high negative ele ctrical charge in the dark. (The

electrical resistance of the OP C drum is high in the abse nce of ligh t. )

• The electric charge on the drum surfa ce dissipates when the drum is

exposed to light. (The conduct ivity of the OPC dru m is great ly enh an ced
by exposure to light.)

• It dissipates an amount of charge that is in direct proportion to the

intensity of the light. That is, whe re stro ng er ligh t is directed to the
photoconductor surface , a smalle r voltage remains.

The OPC drum used in this model has high sen sitivit y, go od color
reproduction, and good rep rod uction of low contrast originals (pen cil
originals, etc.)

2-1

[B]

[G]

DRUM 31 October 1994

1.2 DRUM DRIVE

[I]

[A]

[H]

[D]

[F]

[E]

[C]

The OPC drum [A] is 80 millimeters in diameter and 970 millimet ers lon g. It
turns constantly whe n th e main motor [B] is on.

When the main motor turns on, the drive is transmitte d to the drum in the
following way:

main motor drive gear [C] ⇒ idle ge ars [D] ⇒ dru m drive ge ar [E ] ⇒
drum flange [F] ⇒ drum

When the drum knob is tightened, the right flange presses firmly against the
drum so that the drum is held tightly betwe en the flanges. The drum and
flanges turn together when the main mot or is on. At this time, the drive is also
transmitted to the original feed rollers [G] thro ug h the origina l f eed drive
pulley [H] and belt [I].

2-2

31 October 1994 CHARGE

2. CHARGE

2.1 OVERVIEW

[A]

[B]

Charge

Charge/
Grid
Power
Pack

This model uses a single wire corona unit [A] to cha rge the OPC (org an ic
photoconductor) drum [B ]. The corona unit generates a corona of negative
ions when a high negative voltage is applied to it by the charge/ grid power
pack.

To make the negative corona unifo rm, a grid consist ing of 8 wires is installed
on the charge corona unit betwe en the coron a wire and th e drum. This grid
drains off any charge in excess of –860 volts, thus preventing flu ctu ation of
the charge potential.

Grid

2-3

CHARGE 31 October 1994

2.2 CHARGE CORONA CIRCUIT

Charge/Bias/Grid PP

DC/DC

Converter

DC/DC

Converter

CN340-1

CN243

CN340-2

CN243-8

CN106

CN340-3

CN106

CN340-4

CN340-6

-3

-A8

-A9

-A10

PSU

24V Va

GND

Main Board

0/5

Charge

Grid Drive

0/5

Grid Detect

The PSU supplies +24 volts (VAA) to the charge/bia s/g rid po wer pack as t he
power supply source. Approximately 12 seconds after the copy pro cess
starts, the CPU drops CN106-A 8 fro m 5 volts to 0 volts. This actu at es th e
dc/dc converter within the powe r pack which applies a high negative voltage
of approximately –5.0 kV to the charge corona wire. The corona wire the n
generates a negative corona charge.

The grid limits the maximum corona charg e to –860 volt s. This en sure s tha t
the charge does not flu ctu ate and an even charge is applied to th e drum
surface.

The copy grid voltage and cha rge voltage amounts can be adju sted using SP
# –11 and SP #–10 respectively.

The grid drive signal applied to CN340 -4 is a pulse width mo dulated signal.
As the width of the pulses ap plie d increases, the strength of th e grid charge
also increases. The main board monit ors the grid charge at CN106-A10 and
controls the width of the drive pu lses based on this feedback.

2-4

[A]

31 October 1994 CHARGE

2.3 CORONA UNIT VENTILATION

If ozone produced by th e corona charge stays in the charge coro na area , it
may cause uneven corona charging to the drum. To prevent this, ozone is
vacuumed out t hrough the exhau st fa n [A], and change d to oxygen by the
ozone filter before being blown out of the cop ier.

2-5

EXPOSURE 31 October 1994

3. EXPOSURE

3.1 OVERVIEW

[F] [D] [H]

[E]

[G]

[I]

[A]

Light from the expo sure lamp [A] reflects off the original an d through the fiber
optics [B] to the OPC drum [C]. During exposure, the original moves across
the exposure glass at the same speed as the drum’s peripheral velocity.

The platen plate [D] presses the original [E] flat aga inst the expo sure glass
[F] just above the fiber optic arra y. This en sure s tha t th e imag e is p rop erly
focused. (The original must be with in 0. 2 mm of the exp osu re glass surface.)

The exposure lamp is a 140 V, 26 W fluo rescent lamp.
The original registration sensor [G] detects when the origin al lea din g edge

passes the front of the expo sure glass. The original flatte ne r [ H] ho lds th e
leading edge of the original to ensu re th at origin al reg istra tion sensor detects
the original at the correct timing. The light senso r [I] monit ors th e inten sity of
the exposure lamp output.

[B]

[C]

2-6

31 October 1994 EXPOSURE

3.2 PAPER AND ORIGINAL FEED

3.2.1 Basic Operation (Manual Feed)

[A]

[B]

When the entrance sen sor [A ] of the manual feed table dete cts the leading
edge of the copy paper, th e main mo to r st art s ro ta ting and the drum process
(exposure lamp, change corona,... etc.) begins. The registration clutch is
activated at the appropriate timin g af te r the entran ce sensor [A] detects the
leading edge of the copy pa pe r. The co py pape r is fe d to the re gist ration
roller [B] and stops to wait for the original. "Set Paper" or "RF Se lect " turns of f
and "Set Original" is indicate d on the operation panel.

2-7

EXPOSURE 31 October 1994

[B] [D]

[A]

[C]

[F]

[G]

[E]

The original feed rollers rotate with the rotat ion of the main mo tor. The
original is pulled by the 1st original feed roller [A ] just after th e orig ina l is
placed on the original feed table. The original registration sensor [C] det ect s
the leading edge of the original, and the "Set Orig ina l" indicator turns off. At
the appropriate time, the cop y pape r sta rts to be fed again . The original
passes between the platen plate [D] and exposure glass [E] and from there to
the 2nd original feed roller [F]. The original’s imag e is refle cte d throu gh the
fiber optics array [G] to the drum as th e original passes between th e platen
plate and exposure gla ss. Then, the original exits the machine. At the
appropriate time after either the origin al or cop y paper exits, the image
creation process (drum process) stops. When both the original and copy
paper have exited the machine, the mecha nical drive (main motor) stops.

2-8

31 October 1994 EXPOSURE

3.2.2 Original Jam Check Tim ing

[A]

There is only one sensor (original reg istration sensor) in the original path.
Therefore, original jam cannot be detect ed durin g the time that a maximum
original length (2m) passes this sensor. The original jam check is done after
the leading edge of the original has moved 2.5 m (around 50 seconds). To
stop the machine during operat ion and to protect originals if somethin g wrong
happens to them, the Emergency Stop key [A] should be presse d.

2-9

EXPOSURE 31 October 1994

3.2.3 Drive Mechanism

[D]

[A]

[B]

[C]

The original feed rollers are driven through the origin al feed drive pulley and
belt by the main motor as mentioned in the drum drive section .

The paper registration rollers [A] are rotated by the main motor [B] through
the gears [C] and the paper regist rat ion clutch [D].

2-10

[C]

31 October 1994 EXPOSURE

3.3 FL REGULATOR CONTROL

[B]

A.GND

CN401-4

AAV

CN242-3

CN242-8

CN401-1

CN401-2

T

FL (PWM)

[A]

CN401-4

FL
REGULATOR

Lamp OFF (+5V)

Lamp ON (GND)

T = 1.0 ms
Duty Ratio= 15% to 100%

CN106-A3

CN402-1
CN402-2

CN402-4
CN402-5

CN104-B1
CN410-3

Exp. Lamp

[D]

The FL regulator [A] receive s 24 volt s dc at CN40 1-1 from th e PSU [ B] . The
control signal, which is a pulse wid th modu lat ed (PWM) signa l, is received at
CN401-4. The PWM signal has a period (T) of 1 millisecond and a duty ratio
of 15% to 100%.

The basic light intensity level is determined eith er by the imag e densit y
selected at the operatio n pa nel (ma nual ID control). The CPU uses the light
sensor to monitor the actu al ligh t intensity. The light sensor [C] directly
detects the lamp’s light outp ut and feeds a ligh t intensity signal back to
CN104-B1 of the main board [D]. This feedback allows the CPU to
compensate for variatio ns in light intensity due to the lamp’s age or
temperature.

2-11

EXPOSURE 31 October 1994

3.4 MANUAL ID CONTROL

Manual ID Level

Light Sensor

Output [V]

Manual ID Level

Light Sensor

Output [V]

10.78 8 1.53
2 0.892 9 1.73
3 0.899 10 1.93
4 0.938 11 2.13
5 1.02 12 2.33
6 1.24 13 2.52
7 1.45 14 2.72

3.4.1 Manual ID Control

The user can select one of 14 man ua l ID le vels. Fo r each le vel, the intensity
of the light output by the exposure lamp (as measured by the ligh t sensor) is
fixed. This is shown in the above table . The development roller bias also
varies. (See the section on development bias.)

2-12

31 October 1994 DEVELOPMENT

4. DEVELOPMENT

4.1 OVERVIEW

[D]

[C]

[B]

[A]

When the main motor turns on, the padd le rolle r [A] and deve lop men t roller
[B] start turning. The paddle roller picks up developer in its paddles and
transports it to the develop ment roller. Internal magnets in the deve lopment
roller attract the develo pe r to th e de velo pme nt roller sleeve.

The turning sleeve of the deve lop ment roller then carries the developer past
the doctor blade [C]. The do cto r b lad e trims the developer to the desired
thickness and creates backsp ill to th e cross-mixing mechanism.

The development roller con tin ue s to tu rn, carrying the deve lop er to the OPC
drum. When the developer bru sh con ta cts th e dru m surface, the negatively
charged areas of the drum surfa ce at tra ct an d hold th e positive ly ch arg ed
toner. In this way, th e lat en t imag e is d eve loped.

Negative bias is applied to the development roller to prevent toner fro m b ein g
attracted to non-image areas on the drum that may have resid ual positive
charge. The bias also controls image density.

After turning abou t 10 0 de gre es more, the development roller releases the
developer into th e developer tank. The developer is a git ated by the paddle
roller and the cross-mixing mechanism.

Also, in this machine, rotat ion of the paddle roller and developmen t roller tend
to cause the air pressure in side the unit to be come higher than the air
pressure around the de velo pment unit. Therefore , a hole fitted with a filter
has been added to the top of the unit to relieve air pressure and to minimize
toner scattering.

The toner density sensor [D] is mounted on the upper side of the
development unit to det ect the density of toner in the developer.

2-13

DEVELOPMENT 31 October 1994

4.2 DRIVE MECHANISM

[A]

[C]

[E]

[H]

[F]

[D]

[B]

[G]

[I]

When the main motor [A] is on, the paddle roller [B], development roller [C],
and mixing auger [D] in the development unit are driven through the
development drive chain [E] and gears [F].

The toner agitat or sha ft [G] is rotated through th e ge ars [H] by the toner
supply clutch [I] engaged in the toner supply condition.

2-14

[A]

31 October 1994 DEVELOPMENT

4.3 CROSS-MIXING

[C]

[B]

[F]

[E]

[D]

"Cross-mixing" keeps the developer’s toner and carrier evenly mixed and
evenly distributes the de velo pe r within the development unit. Cross-mixing
also agitates the developer to gen era te the nece ssary triboelectric charge on
the toner and carrier particles.

The arrows in the above illustration show the developer movement direct ions
within the machine. The developer that is attracted to the develo pme nt ro ller
[A] is split into two parts by the doctor blad e [B ]. One part (the magnetic
brush) goes on to develop the latent image on the drum. Howe ver, the oth er
part is trimmed off by the doctor blade and directed to the backsp ill plate [C].

As the developer slides down the backsp ill plate to the paddle roller [D], part
of the developer falls int o the auger inlet [E] and is transp ort ed to th e left side
of the unit by the mixing auger [F], where it drops on to the pad dle roller. The
amount of developer mo ved to the right by the backspill plate is equa l to th e
amount moved to the left by the mixing auge r.

2-15