Fukuda Denshi FX-2111 ECG Service manual

S

E

R

VIC

E

M

A

N

U

A

L

Electrocardiograp

FX-2111

4R204

3

h

FUKUDA DEI

MSHI CO., LTD.

Copyright © 1997 by Fukuda Denshi Co., Ltd.

No part of this document may be copi

or transmitted in any form without

the prior written permission of Fukuda

Denshi Co., Ltd

.

ed

Manufactured in Japan

Forewor

d

We list up here the warning marks used in Fukuda operation an

service manuals

.

A

When you sen/ice the FX-2111, read this service manual thorough

ly and pay attention especially to instructions bearing the fol­lowing marks:

Warning Marks

Warning marks used in operation and service manuals and labelled

on the instrument have the following meanings:

Read them carefully to understand the meanings and make sure of

the significance of each particular

This mark is used to indicate the direct hazard

A

Danger which may lead to the death or serious injury of th

person, may wholly damage the instrument, or ma

cause fire hazard, unless the instructions writte

there are followed.

This mark is used to indicate the indirect potentia

.

d

-

s

e

y

n

l

A

A

Other Mark

Warning hazards which may lead to the death or serious injury

Caution which may lead to a mild or medium injury of th

NOTE

0

A

of the person, may wholly damage the instrument

or may cause fire hazard, unless the instruction

written there are followed

This mark is used to indicate the possible hazard

person, may partially damage the instrument or may

erase data from the computer.

"NOTE" is not warning instructions but offers infor

mation to prevent the person from doing erroneous

sen/icing

s

Notice to indicate general unspecific prohibite

matters

Notice to indicate general unspecific caution, warn-

ing or hazard

.

.

.

.

s

s

e

-

d

This service manual describes technical information on FX-2111 t

aid the service engineer in troubleshooting.

The manual is intended to be used by service engineers of Fukuda

representatives and authorized technical staff concerned with medical elec
tronic equipment. Description includes repairing and assembling methods
of each component unit of FX-2111. For parts lists and diagrams, refer to

the Part II of the service manual.

The service manual consists of the following nine chapters:

1

.

General Descriptio

n

The outline of FX-2111, specifications, controls and indicators are

described

2

.

Circuit Descriptio

Circuit configuration and functions are explained

3

.

Troubleshootin

Troubles vs. causes and countermeasures are described

Maintenance

4

.

Procedures to replace the power fuse, ROM and battery and to perfor

self-test are described

.

n

.

g

.

m

.

o

-

5

.

Periodical Inspectio

n

Inspection procedures to prevent troubles and ensure safe and com-

plete operation of the instrument are described

6

.

Circuit Diagrams

7

.

Assembly Diagram

8

Electrical Parts Lists

.

9

.

Structural Diagram

s

s

.

A Caution

0

. Never remodel Fukuda medical electronic equipment

. The service manual is intended for the service

engineers of Fukuda representatives and the techni
cal staff concerned with medical electronic equip
ment. Servicing, reassembling, and adjustment shall

be performed by authorized service engineers.
. Prepare proper facilities and tools when servicing
. Be sure to follow the instructions of operation manua

when operating the instrument. For operating precau

tions, refer to the operation manual.

.

-

-

.

l

-

i

i

A Servicing Precautions

A Cautions listed below are the instructions of prohibi

ing, and caution described in this service manual. When taking th

procedure bearing the following mark, read the description thoroughly

then start the task

When checking the power supply and related circuits for troubleshoot

ing, take sufficient care to avoid a short circuit.

When checking power fuses, be sure to turn the power off and discon

nect the power plug from the wall outlet beforehand.

The inserting part of key connector is made of carbon. Avoid frequent

repeated disconnection and connection

When replacing power fuses, be sure to turn the power off and discon

nect the power plug from the wall outlet beforehand.

.

A Caution

A Caution

A Caution

A Caution

.

t

danger, warn

,

(page 3-2

(page 3-3)

(

page 3-8)

(page 4-1

-

e

,

)

-

-

)

-

A Caution

When replacing the ROM, be sure to turn the power off. Also, take car

to install the ROM in correct position.

A Caution

When replacing the battery, be sure to turn the power off and discon-

nect the power plug from the wall outlet beforehand

(

page 4-1)

(page 4-2

.

e

)

iii

A C

aution

(page 4-6

)

Disassembling/Reassembling Precaution

s

Be sure to disconnect the power cord and make sure the instrumen

is turned off before disassembling or reassembling

. Do not remove the battery before disconnect any PC board

.

.

Take care that repeated disconnection of the key panel and senso

board may result in poor contact.

Use proper tools to loosen screws.

. When reassembling, make sure that all screws are securely tight

ened and all connectors are completely inserted

PC Board Handling Precaution

s

.

. PC boards are equipped with highly sensitive components to static

electricity

. PC boards are highly sensitive electronic device

.

Put removed PC

.

s

boards in a proper protective bag or take appropriate measures to

protect them.

Handle PC boards carefully. A shock to them may damage the com-

ponents

.

Never insert a connector to the powered PC board nor remove the

powered PC board.

t

r

-

A Caution

(page 5-2

If you find a value which exceeds the allowable level, be sure to let

the user avoid using the FX-2111. If the user operates the FX-2111 a

it is, he/she may receive an hazardous accident

Equipment Classificatio

n

The FCP-2155 is classified into the following equipment

1

.

Protection against electrical shoc

Class I

2

.

Type against electrical shock

Applied part: Type C

3

.

Degree of protection against harmful water invasion

F

k

.

:

Other equipment

4

.

Degree of safety in using under air-inflammable anesthetic gases o

oxygen/nitrous oxide-anesthetic gases

Equipment used under an environment containing no inflammabl

anesthetic gases or no inflammable cleaning agent

.

)

s

r

e

5

.

Running mod

Continuous running mode

e

i

v

CHAPTER

1

Outline of the FX-2111

1

.

2

.

Specifications

2

.

1 Electrocardiograph Section

2

2 General

.

2

3 Environmental Conditions

.

Controls and Indicators

3

.

3

.

1 Top Panel

3

.

2 Side Panels, Left and Right

3 Bottom Panel

3

.

General Infor

matio

n

1-1

1-1
1-1

1-2

1-2
1-3

1-4

1-4

1-4

1

Outline of the FX-2111

.

The FX-2111 is the easy-to-use single-channel electrocardiograp

featuring a simple operation

panel. The compact yet high-performanc

design makes it suitable not only for use in the consultation room bu

'

also for-carrying in a visit to the hospital ward or patien

examination at an emergency site

.

s home an

t

It has a high-density thermal dot printer incorporated to provide clear

ECG recording. The FX-2111 can operate on either AC line or rechargea

ble Ni-MH battery

2

.

Specification

2

.

1 Electrocardiograph Sectio

Input circuit

Leads

:

Input impedance
Input circuit current

Calibration voltage:

.

s

n

:

:

:

Floating from the groun

Standard and Cabrera 12 leads

20MQ min. (referred to 10Hz

5x10"8 max.

1mV within ±5

%

d

)

Common mode rejection: 10mm or less per IEC 62DC06 test

Polarization voltage:

Time constant

Sensitivities

:

:

Frequency response:

AC filter
Muscle filter

:

:

DC input:
Display

:

metho

±300mV min.

3.2 sec min

1/2, 1 and 2 cm/m

0
50/60Hz, -20dB or lower

35 to 45Hz, -3dB (-6dB/oct)

10mm/0.5V, unbalanced, 100kfi min.

Liquid-crystal display, 20 chars, x 2 lines

d

.

V

.

05 to 150Hz (within -3dB)

(character: 5x7 dots)

Recording system:
Paper speeds:
Chart papers

-

Roll paper:

Z

-fold paper

AID conversion:

Sampling rate

:

:

Thermal dot printer, 8 dots/m

25 and 50 mm/sec within ±3%

63mm or 50mm wide x 30m lon
63mm or 50mm wide x 20m long,

75mm/fold

12 bits
1ms

m

g

h

e

t

d

-

1-1

2

2 Genera

.

l

Safety:

Power requirements-

AC operation

DC operation

Dimensions:

:

:

Weight:

2

3 Environmental Condition

.

Operating

-

Temperature:

Humidity:

Atmospheric pressure: 70 to 106kP

Transportation & Storage-

Temperature:

Humidity:

Atmospheric pressure: 70 to 106kPa

I EC 601-1 Class

.Type C

I

F

. Internally powered equipment Typ

CF (IEC 601-1

)

115V AC, 50/60H2; 19VA max.

230V AC, 50/60Hz; 19VA max.

9

.

6V, 7W max. (rechargeable Ni-MH

battery

)

Continuous operation: approx. 120 mi
at 20oC (according to IEC 62D Testing

Method)

Charging time: within 3 hours
26 (W) x 18.2(D) x 6.3(H) c

m

Approx. 1.7kg (excluding battery)

s

10 to 40o

C

30 to 80%RH (no dew condensation)

a

-10 to 40oC

10 to 95%RH (no dew condensation

e

n

)

-

2

1

Controls and Indicator

3

.

Top Panel

s

@ Paper Magazin

® Potential Equalizatio

Termina

l

n

e

Left Pane

o

0 0

F

X Liquid-crystal Displa

3

1

-

k

»

(D Operation Pane

l

«

0

3

D

© Power Connector

© Main Power Switch

Right Panel

Q

@ DC Input Termina

© Lead Connector

y

l

l

© Fuse Holder

Bottom Pane

o

{

*

l

@

o

I i

<

"

© Rechargeable feattery Roo

m

iii

s

§

)

~0~

0

®

0

-

3

1

3

.

1 Top Pane

l

© Display

:

© Operation Panel

ON
OFF

Mode

Sensitivity

Lead Select <

Reset

1mV

Start/Stop

Indicates current status such as recording mode, lead, sensitiv
ity, heart rate, or program setting

.

-

:

Turns the FX-2111 on in DC operation.
Turns the FX-2111 off in DC operation.

Pressing this key during AC operation lets the FX-2111 enter th
charge mode.
Select a mode in the following order when pressed during cessa­tion of recording

-> Automatic recordin

|

Holding this key during automatic recording lets the FX-2111 record
the current lead continuously until detached.

:

g -» Manual recording -> Programming -|

Holding this key during manual recording lets the FX-2111 recor

an event mark until detached.

Selects a recording sensitivity
Select a lead for recording. In programming mode, these keys allow

you to select a setting value

.

.

Resets the measuring circuit while held during recording. In
programming mode, this key selects a setting parameter

Applies a 1mV calibration waveform when pressed during record

ing. In progra

mming mode, this key selects a setting parameter

Starts the FX-2111 recording the ECG waveform. Another press stops

it from recording

.

.

e

d

-

.

© Paper Magazine

3

.

2 Side Panels, Left and Right

® DC Input:

© Lead Connecto
© Power Connecto
© Main Power Switch

:

Accommodates a chart

Inputs external DC signals with a sensitivity of 10mm/0.5V.

r

r

Connects to the lead cable

Connects to the power cable.

:

Turns AC power on/off

@ Potential Equalization

Terminal:

Makes the FX-2111 equipotential to another instrument used in com

bination with it. To that effect, connect both instruments to a

common grounding conductor using an optional grounding wire

3.3 Bottom Panel

© Battery Room

© Fuse Holders:

:

Houses the rechargeable Ni-MH battery

Have power fuses inserted

paper

.

.

.

-

.

.

.

1-4

CHAPTER

2

Circuit Description

Introduction

1

.

2

.

Isolated Input Circuit

2

.

1 Buffer Amplifier and RF Driver

2 Lead Network and Lead Selector

2

.

2

.

3 Preamplifier and 1mV Generator

2

4 R-wave Detector and Overinput Detector

.

2

5 Amplifier Control

.

2

.

6 Signal Isolator

7 Power Isolator

2

.

3

.

Middle Amplifier and AID Converter

3

.

1 Middle Amplifier and DC Input

2 AID Converter

3

.

Motor Control

4

.

Sensor Circuit

5

.

5

1 Detection of Magazine Open Condition

.

5

2 Detection of Paper End and Paper Marks

.

CPU Circuit

6

.

1 Reset Circuit

6

.

2 CPU, ROM and RAM

6

.

6

3 Gate Array

.

LCD Control Circuit

7

.

Thermal Print Head Control Circuit

8

.

9

Memory Backup Circuit

.

10. Power Supply and Charging Circuit

10.1 Introduction

10.2 Rectifier/Smoothing Unit and ON/OFF Control

10.3 + 10V and +5Vd Power Generators

10.4 ±5Va Power Generator

10.5 +24V Power Generator

10.6 Charging Circuit

2-1

2-2
2-2

2-3

2-3

2-4

2-5
2-5

2-6

2-6

2-6

2-7
2-8
2-8

2-9
2-9

2-9

2-9
2-9

2-9

2-1
2-1

2-1

2-1

2-1

2-1

2-1

2-1
2-1

2-1

1
1

2

3

3

3

4

5
5

6

1

Introduction

.

The FX-2111 is composed of the following circuits:

(1) Main Board PCB-6409

-Isolated input circuit

-Middle amplifier and AID converter circuit

-Motor control circui

-Sensor circuit

-Reset circui

t

-CPU circuit (CPU

-LCD control circui

t

ROM, RAM, gate array

,

t

)

-Thermal print head control circuit

-Memory backup circui

t

-Power supply and charging circuit

(2) Sensor Board PCB-6239

(3) AC Inlet Board PCB-6410

ECG signals input through the lead connector are amplified by the

isolated input circuit and the middle amplifier circuit, then converted fro

m

analog to digital signals by the AID converter circuit. The digitized signal

are digitally filtered, if the filter is set to ON, then sent through the gat

array to the thermal print head control so that they are recorded as ECG
waveform by the thermal print head.

s

e

During these processes, the heart rate detected by a hardware

technique and operation status such as filter ON/OFF setting are displayed

on the LCD.

The power supply provides circuits with necessary powers. The
charging circuit, if activated, charges the Ni-MH battery in AC operatio
or transfers the power from the Ni-MH battery to the power supply. The

state of battery is indicated on the LCD.

:

"

r

e

O

3

Isolated Input Circuit

D

C

Input

D

C

Motor

Thermal ]

Print

Hea

d

Motor

Control

Thermal

*

Print it

.

Head [

Control

PCB-640

-

I

5 M

m

J Gate Array

9

i5V

I0

V

5V

.

V

Power Suppl

ZEE

'

-

/Charging;-

'

i

-24

f

VDO
+

2

:pcb-64i

y

;

AyiCircuil;--

*

t

:

'

,

CPU Circuit

Key Panel

AC Inle

AC Powe

NiM

H

Battery

o

t

r

n

LCD

LCD
Control

1

PCB-

Senso

r

Board

Overall Block Diagram

2

-

1

623

.

9

Backu

Circuit

p

2

.

Isolated Input Circui

t

The isolated input circuit is composed of the following

(1) Buffer amplifier and RF drive
(2) Lead network and lead selecto
(3) Preamplifier and 1mV generato

(4) R-wave detector and overinput detecto

r

r
r

r

(5) Amplifier control
(6) Signal isolator

(7) Power isolato

-

R

L

F

C

I

I

C

6

RF Drive <-

5

2

D c

-

5

"

1

5

r

I

O

-

5 5

t a

-

D

5

-

I 2

.

-

5

-

5

5

5

I

"

S

T

R

F

-

5 Preamplifie

1mV

Amplifier

Control

r

RESET

"

> Signal

:

ECG

Isolato

Signal

Isolato

r

r

Block Diagram of Isolated Input Circuit

2

.

1 Buffer Amplifier and RF Drive

oac- Hit icr

9 ISO

*

3

Overinput

R

-Wave Detecto

Circuit

/

r

5

r

.e-

(Photo

Coupler

i
i

Power

Isolator <

)

I

-

I

0

.

Since the buffer amplifier should input signals with high impedance
and output them with low impedance, it is configured as an impedance
conversion circuit using an operational amplifier. The circuit shown abov

is individually applied to all leads except for RF (right foot). Also, a limite

using a dual transistor is mounted for protection against overinput

The RF driver feeds back the composite signal of limb leads to th

.

right foot for improved common mode rejection ratio.

-

2

2

e

r

e

2

2 Lead Network and Lead Selecto

.

O

K

211
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0

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200

0-<

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T

r

> -

Lead Select Signals

B

C

Leads

STD

A

0 0 0 0

10 0 0

0

I

I

III
V

r

a

10

1

10

0 0

aVL 10

E

l

aVF

0 1

V

I

V

2

V

3

V

4

V

5

V

6 0

1

1

0 0 0 1

10 0 1

0

1

1

1

0

D

1

1
1

1

0 1

0 1

1

0

0

0

0
0

0

1

The lead network is formed with resistors and lead selector, with multi-

plexors IC36, IC38, IC41 and IC4. Input signals to multiplexors are selecte

from RA, LA, LF, and CI to C6 according to four signals of A, B, C, and

D

then synthesized to produce each ECG lead (see table above).

,

2

.

3 Preamplifier and 1mV Generato

C-1 f

o

.ao

-II

r

1

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C

Signals output from the lead selector (multiplexors) are amplified 8

times by a differential amplifier, then 25 times by a noninverting amplifier,
thereby letting the isolated input circuit amplify the input signals by 200

times in total. Signals output at the first stage are sent to the overinpu

detector.

d

t

-

3

2

The 3.5Mfi resistor and 1|jF capacitor set the time constant at 3.

seconds

2

.3.

.

2 1mV Generator

The 1mV generator divides the high-precision voltage reference out-

put of 1.235V by a high-precision resistor, thereby applying a 8mV voltag
to the preamplifier when the 1mV application signal is at a low level

2

.

4 R-wave Detector and Overinput Detector

era Q.Qit

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2.4

1 R-wave Detector

.

RA and LF signals of lead network are synthesized to II lead. The R

wave detector detects R wave by picking up R-wave component from the

II lead signal through a band-pass filter, then sending it to a comparator.

2

.4.

2 Overinput Detecto

r

The signal output at the first stage of preamplifier is sent to a com

parator and if the signal exceeds ±360mV, the output of the comparator

becomes inverted

.

Signals output from the R-wave detector and overinput detector ar

adjusted in the pulse width by the multivibrator IC40 (TC4538), then input

into the photo coupler.

+

0

31

V

.

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1T6

3

v

-

0.31V

-

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2. 9V

O

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-

2. 9V

TP1

TP2

9

0

-wave Detection

R

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Wavelorm

Overinput Detection Wavefor

2

-

4

* 170»S

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2

.

5 Amplifier Control

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AMP

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DAT

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4

This circuit picks up a reset, 1mV,or lead select signal from the seriall

transferred amplifier control signals

!<-% 1ms

2

-

DOD

7

D6D

5

D4D3D

i
i

2

OLD DATA <-

8ms

Response time: 32ms + a max.

K

2

.

6 Signal Isolato

K

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The signal isolator modulates input analog ECG signals with FET

Q31 and Q32 and pulses TRF1 + and TRF1 -, then transfers the modulated

signals through the T1 isolation transformer (1:1). FETs Q22 and Q2

demodulate the signals. A low-pass filter formed with capacitors an
resistors in two stages eliminates noise in the demodulated signals

.

Digital signals (AMPCLK, AMPDATA and HR) are transferred using a photo

coupler

.

2-5

s

3

d

2

7 Power Isolato

.

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ECG signals demodulated at the isolated signal transmission section

are output to the middle amplifier just after passing through a low-pass
filter formed with capacitors and resistors in two stages. The middle am-

plifier amplifies the input signals 1.25 times to a total gain of 250 times

and sends them to the AID converter. Signals output from the AID converter

are digitally filtered with a software technique. The isolated input circui

and the middle amplifier are designed so as to provide a general hard­ware frequency response of 150Hz (-3dB)

.

The DC input amplifies input signals 0.5 times, then sends the signals
to the AID converter through a buffer amplifier

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The A/D converter is a single slope type. It is composed of a triangula

wave generator, sample & hold circuit, and comparator. The comparator

compares input signals with ±3.2\/ triangle wave generated at every 1ms

The signals are then converted from the voltage to a pulse width and trans-

ferred to the gate array. In the gate array, the pulse width is counted, the

converted into a digital value.

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Besides ECG signals, the AID converter digitizes DC input signals

battery voltage, thermistor signals of thermal print head, and the refer­ence voltage of 2.5V for calibration of A/D conversion.

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The motor to drive the recorder is the DC motor which has a photo

sensor built in for detection of motor speed. The PLL control IC25 com-

pares a signal detected by the photo sensor with the reference frequency

in phase, thereby providing a motor control signal at pin 13 of IC25

.

The motor control signal goes to the integrator circuit formed with

R140, R142, and C64 and is made by a proper motor drive voltage of the

PWM control IC24.

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1 Detection of Magazine Open Condition

When the paper magazine is open, the microswitch SPVC2-1 is turne

off to send an interrupt signal to the gate array. Magazine opening is de
tected with the fall signal and magazie closed is detected with the rise signal

5

.

2 Detection of Paper End and Paper Mark

s

A reflection type photo interrupter acknowledges a black paper mark

or paper end status (no paper remaining) if receiving no reflection from the

location of paper. It discriminates between paper end status and paper mark

based on a duration of the low level starting from a fall signal.

CPU Circui

6

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The CPU circuit is composed of a reset circuit, CPU, ROM, RAM, gate

array, and backup power circuit.

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Using NJM2103, the reset circuit generates a reset pulse as well as

monitoring the battery voltage. It outputs the reset pulse when Vdd falls

to lower than 4.27V or when it receives a signal from WDT.

As for the battery voltage, the reset circuit monitors the power voltage

divided by resistor and when the voltage becomes lower than 7.5V referre

to the battery terminal, it outputs a pulse to the LOWS terminal to tur

the power off. To protect the output pulse against power fluctuation noise,

a filter formed with a capacitor and resistor in one stage and a Schmid
trigger inverter are provided

2 CPU, ROM and RA

6

.

The CPU is HD63B09E. It controls the overall circuit of the instrumen

.

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through the gate array. The ROM is 64K-byte AM27C512-150DC and th

RAM is 8K-byte SRM2264LM12. By changing the jumper connection, th

ROM can be replaced with a 128K-byte ROM and the RAM, with a 32K-

byte RAM (with a data holding current of lower than 2\iA)

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The gate array is FD88007-AC with a clock frequency of 16MHz. Its

control signals are as follows:

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There are three types of interrupt signals-NMI, FIRQ and IRQ. Al

these signals, active at low level, are output to the CPU

-NM

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Output at every 1ms
Output at every 10ms.

Q

Output when any one of MAGAZIN, MARK, HR, LOWB, CH

IRQ

and AC/DC signals is input.

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a = 390ms (9.75mm) with a paper speed of 25mm/sec

190ms (9.75mm) with a paper speed of 50mm/sec

NOTE: ACDC, CHG IRQ, and MAGAZIN DOWN signals are detected at

their rise and others are at their fall

6.3

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Chip select signals are all active at low level

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RD: Read enable signa

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NOTE: LCD signal differs from the above since the memory is ready. (See

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LCD Control Circui

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ly with the CPU. However, E and Q clocks make the bus timing as shown below

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LCD control circuit.)

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Since the LCD (NDM202A00) has a controller built in, it is interfaced direct-

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Address

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Thermal Print H

8

.

A waveform is traced at every 1ms and alphanumerics are at ever

6ms with a paper speed of 25mm/sec or every 3ms with a paper spee

of 50mm/sec. The RAM for the thermal print head control uses 4K-byte

for alphanumeric data. This circuit controls dot heating temperatures based
on previously printed data to provide a proper printing condition

When the paper is not driven or when the magazine is open or ther
remains no paper in the magazine, the circuit generates TOFF signal t
shut off power supply to the thermal print head at the FET Q24, thereby

protecting the thermal print head

There are four control signals of CLOCK, DATAIN, LATCH, and STROBE

The STROBE signal is varied in pulse width according to thermal print

head temperatures

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The battery-backed RAM SRM2264LM12 is installed to keep program

contents when the FX-2111 is turned off. The RAM should feature a data

holding current of lower than 2nA

When the FX-2111 is turned on, Vdd is supplied to the circuit and

turns Q6 and Q7 on to send +5\/ Vdd to the RAM.

When the FX-2111 is turned off, Q6 and Q7 are turned off but the back

up lithium battery supplies +3V to the RAM to let it keep t

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10. Power Supply and Charging Circuit

10.1 Introduction

The power supply transforms the AC power by the transformer o
receives DC power from the battery, then regulates the power to stabilize

voltages required by respective circuits.

The FX-2111 is equipped with a charging circuit to permit the use
to charge the Ni-MH battery

AC Powe

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Transformer

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Rectifier

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10.2 Rectifier/Smoothing Unit and ON/OFF Contro

l

10.2.1 AC Operation

The AC power voltage is transformed by the transformer, then rectified

by D1 to D4 and smoothed by C136. D1 to D4 are Schottky diodes with

low Vpand form a bridge circuit. This rectifier circuit suppresses voltag

decrease and features less heat generation.

10.2.2 ON/OFF Control

In battery operation, a press of the ON key switches FET 04 on an
electrifies D7, thereby making the base of 05 driven. If the operato
detaches the finger from the ON key, 04 is kept on and the power is
supplied to the FX-2111

The battery voltage is detected via D6. If the voltage between battery

terminals is lower than 7.5V or so, the gate array generates POWER OFF

signal to turn 03 on and cancel the bias voltage of 05, thereby switchin

04 off. As the result, the FX-2111 receives no power supply and is turned off

Similarly, a press of the OFF key cancels the bias voltage of 05, thereby

turning the FX-2111 off. In AC operation, 01 is on; therefore the base of

05 cannot be driven and 04 cannot be kept on, thereby making battery

operation impossible.

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The dropper type 4-terminal regulator IC22 is used to regulate unstabi-

lized IOVnU) stabilized lOV. R118 and R119 are to set the output voltage.

The 10V power is supplied to the m

otor and the 5Vd power generator.

If the battery voltage becomes lower than 10V in battery operation

IC25 drops the voltage to several ten millivolts

10.3.2 5Vd Power Generato

r

.

C7 is a drop type low-loss 3-terminal regulator. It produces regulated

5V power from 10V. IC7 can operate if an input-output voltage difference

becomes up to 0.5V and thus it can output the stable 5V power if the inpu

voltage fluctuates due to lowered battery voltage.

The 5V power thus produced is supplied to the CPU and other digital

circuits.

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Using the unregulated 10Vn power from the AC power supply or the

battery, the 3-terminal regulator ICQ produces +5V. IC10 is a CMOS inverting

type switching regulator, in which the output voltage is fixed and which

inverts the input +5V and outputs -5V. A capacitor at the output is an

organic semiconductor capacitor which features superior characteristics

at low temperatures and least leakage current

.

±5V powers thus produced are supplied to analog circuits such a

operational amplifier

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Using the unregulated 10Vn power from the AC power supply or th

battery, the +24V power generator, a boosting type DC-DC converter

produces 24V power for driving the thermal print head and charging th

battery

.

IC6 is a PWM-controlled switching regulator. R22 and C18 determine

the oscillation frequency. The PWM control is performed at approximately

170kHz to drive Q9 at a high speed. While Q9 is on, the current flows t
LI which in turn stores the energy. When Q9 is turned off, the stored energ

becomes a counter-electromotive force and is stored in C137 via D13. By

repeating a series of these operations, the +24V power generator ca

produce an output voltage larger than the input voltage. R41 and R42 se

the output voltage at 24V. R24 checks for an overcurrent and a charac-

teristic is provided to gradually lower the output voltage when the load

current increases to over 0.4A.

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The 24V power thus boosted is used to drive the thermal print head

When the thermal print head is printing, a signal from pin 21 of the gat
array drives the base of Q15 to switch FET Q24 on so that the -I-24V i

supplied to the thermal print head. When the thermal print head is no

printing, Q15 and Q24 are off and the thermal print head is not supplied

with power.

Pin 16 of IC6 outputs 2.5V, which is used by the AID converter an

the thermistor temperature detector of thermal print head

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The charging circuit is equipped with the quick charging IC18 (bq2003),
which performs constant current control as a frequency modulation con­troller for switching regulation of the charging current and monitors th

battery temperature and voltage and the charging time to ensure proper

charging. It also checks whether or not the Ni-MH battery is connected

and enables charging only when the battery is connected.

e

In AC operation, the circuit is supplementarily charging the batter

even if the FX-2111 is not placed in charging mode

10.6.1 Starting the Charging Circui

t

.

When the OFF key is pressed in AC operation, Q11 is turned on t

supply +5V for operation of the IC. Since the base of Q12 is driven b
turning Q11 on, Q11 is kept on. When +5V is supplied to IC18, the charg

ing circuit automatically starts operating.

10.6.2 Charging Temperature and Voltage Monitoring/Contro

Charging is limited by battery temperature and voltage so that it i

made in a preset range.

To monitor the battery temperature, a thermistor (with negative tem-

l

perature coefficient) is installed in the battery pack. The thermistor output

a voltage signal to pin 6 (TS) of IC18 and charging is enabled if the voltage

is within the preset limits in voltage converted from battery temperature

The sensitivity of a battery temperature rising ratio (AT/At) is adjusted by

resistances of the thermistor and R59, R61, and R62 on the charging circuit.

The battery voltage is divided to a voltage per cell by R58 and R6

which are connected between battery terminals, then sent to pin 7 (BAT

of IC18. Charging is enabled if the voltage is within the preset limits i
voltage per cell.

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Divided +5V powers of R84 and R85 are used to determine the maxi­mum cell voltage (MCV) of the battery and the maximum voltage (TCO
for the battery temperature to stop charging, respectively. They are outpu
to pin 10 (TCO) and pin 11 (MCU) of IC18.

Preset battery temperature limits and cell voltage limits are as follows

. Battery temperature limit

s

Minimum charge enable temperature limit LTF: Approx. -50C

(voltage level 2.0V)

Maximum charge

(voltage level 1.13V)

enable temperature limit HTF: Approx. 60o

C

High temperature to stop charging TCO: Approx. 650C

(voltage level 1.01V

. Battery cell voltage limits to enable chargin

Minimum: Approx. 1.0V

Maximum: Approx. 1.78V

That is, when the charging circuit is turned on, it starts charging the
battery if the battery temperatre is within a range of 50C to 60oC and
the cell voltage is within a range of 1.0V to 1.78V. If either one of the above

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conditions is not satisfied, it does not start charging the battery but i
placed in a standby status until both conditions are satisfied.

Once the charging circuit starts charging the battery, the charge com­plete system described later will be effective. However, if the maximum
cell voltage of 1.78V is exceeded before the start of charging, the charging

circuit judges the battery abnormal and does not start charging

.

10.6.3 Charge Current Control

The power required for charging is supplied from the 24V powe
generator. The charging current to the battery is detected by the resistor

R18 then sent to pin 9 (SNS) of IC18. The output of pin 14 (MOD) of IC1
is switched based on the voltage value of R18 to switch Q17 on/off, thereb

making the current constant. The charging current is set at approximatel

0

.

45C (480mA).

Q16, D22, and Q10 form a MOS FET driver and level shifter circuit to

heighten the switching frequency.

10.6.4 Charge Complete System

When the battery temperature and cell voltage are within the respec-

tive ranges, the charging circuit continues to charge the battery until on
of the following five conditions is satisfied

. - AV detected

. - AllAt (temperature rising ratio) detected

. Maximum temperature of 650C to stop charging TCO reached

. Maximum charging time of 3 hours reached

78V reache

. Maximum cell voltage MCV of 1

.

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Usually, the charging circuit stops charging by detecting -AV

However, if charging is started at high ambient temperatures, the chargin

circuit may detect the maximum temperature (TCO) to stop charging. Also

as a safety measure against no - AV detection, the maximum charging
time of three hours is set by timer and TM1 and TM2 signals at pins 4
and 5 of IC18, respectively, stop the charging circuit from charging if the

time is reached

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In AC operation, supplemental charging is made by R66. In AC oper

ation, Q14 is on and the base of Q13 is driven to supply R66 with the 24V

power. The current of which the value is determined based on a voltag

difference at R66 flows for supplemental charging. However, if the batter

is not connected, Q8 is turned on and Q14 is kept on, thereby disablin
supplemental charging and at the same time cancelling the bias voltag

of Q12. Thus, the 5V power to operate the charging circuit is not held an

charging is impossible.

The charging circuit outputs CHG IRQ and CHG STATUS signals. When

the circuit is supplied with 5V, the CHG IRQ signal becomes high level

to indicate the instrument is placed in charge mode. The CHG STATU
signal is output from pin 13 (CHG) of IC18 to indicate the current charging
status. If the battery is not connected, the CHG IRQ signal cannot becom

higher than 0.7V since D15 is electrified. Thus, the instrument is not placed
in charge mode

.

The CHG signal is output in the following manner:

CHG STATUS Output Level

Lo

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Abnormal power voltage

Hig

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Continuou

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Start of chargin

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Charged

CHG IRQ Signal

CHG STATUS Signal

in ordinary charging

CHG STATUS Signa

with some pending of charging

CHG STATUS Signa
with abnormal battery voltage

l

l

Continuous (rise)

1

375s ± 0.225

.

125ms ±20ms 125ms ±20ms

CHG swilch ON

2. 0s

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Start of Charging Mode Charolng In Progres

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CANT CHARGE" message appears aller 5 seconds Irom the start

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No charging mad

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Charging in Progres

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Churging Conipleloi

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-18