Datex-Ohmeda 3770 User manual

6050-0004-915
Printed in USA
3770/3775 Pulse Oximeter
Service Manual
%SpO2
2798
♥
%SpO
2
♥
2798
Not for continuous monitoring

3770/3775 Pulse Oximeter
Service Manual

Important
This manual is subject to periodic review, update, and revision. Customers are
cautioned to verify that the information in this manual applies to the software and
hardware present in the equipment.
Attention! Consult the accompanying instructions before using this
device.
This device performs as described in this manual, and in accompanying labels
and inserts, when assembled, operated, maintained, and repaired in accordance
with the instructions provided.
This device must be cleaned and checked periodically. o not use a defective
device. Parts that are broken, missing, plainly worn, distorted, or contaminated
should be replaced immediately. If repair or replacement become necessary,
request service advice from atex-Ohmeda (information is listed on the back
cover). o not repair this device or any of its parts other than in accordance with
written instructions provided by atex-Ohmeda.
The user of this device shall have the sole responsibility for any malfunction that
results from improper use, faulty maintenance, improper repair, unauthorized
service, damage, or alteration by anyone other than atex-Ohmeda.
The safety, reliability, and performance of this device can be assured only under
the following conditions:
• If it is used according to the accompanying operating instructions.
• If fittings, extensions, readjustments, changes, or repairs are carried out by
agents authorized by atex-Ohmeda.
• If it is used in buildings having ground equalization wiring that complies with
relevant local standards and regulations.
Trademarks
atex® and Ohmeda® are the property of Instrumentarium Corp. or its
subsidiaries.
FlexConnect is a trademark of atex-Ohmeda, Inc.
Cidex is a registered trademark of Johnson & Johnson
uracell is a trademark of uracell, Inc.
Eveready is a trademark of Eveready Battery Company, Inc.
Formula 409 is a registered trademark of Clorox Company
Hewlet Packard is a registered trademark of Hewlett-Packard Co.
Kodak is a trademark of Eastman Kodak Company
Panasonic is a trademark of Panasonic Industries, Co.
Rayovac and Renewal are registered trademarks and Reusable Alkaline is a
trademark of Rayovac Corporation
Top Crest is a trademark of Safeway, Inc.
Windex is a registered trademark of The rackett Company
All other product and company names are the property of their respective owners.
Text revised: May 2000
© 1997, 1999, 2000 atex-Ohmeda, Inc. All rights reserved.

Contents
i
1/Overview
Related information...........................................................................................................1-1
Technical competence.....................................................................................................1-1
General description.....................................................................................................................................1-2
Theory of operation.....................................................................................................................................1-2
Calibration............................................................................................................................................1-3
Functional components.............................................................................................................................1-4
igital board........................................................................................................................................1-5
80-pin board-to-board connector...................................................................1-5
Analog board.......................................................................................................................................1-6
Specifications..................................................................................................................................................1-7
Electromagnetic effects.................................................................................................................1-7
Environment..........................................................................................................................1-7
EMC performance..............................................................................................................1-7
International Electrotechnical Commission (IEC) classifications.........................1-7
Compliance with standards.......................................................................................................1-8
Oximeter................................................................................................................................................1-8
efault settings.....................................................................................................................1-8
General......................................................................................................................................1-8
Visual displays and indicators.......................................................................1-8
imensions................................................................................................................1-8
Power............................................................................................................................1-9
Circuitry......................................................................................................................1-9
Sensor emitter wavelength ranges..............................................................1-9
(3775 only) Audio indicators...........................................................................1-9
SpO2...........................................................................................................................................1-9
Range............................................................................................................................1-9
Accuracy.....................................................................................................................1-9
Calibration.................................................................................................................1-9
Interfering substances.........................................................................................1-9
(3775 only) Alarm limits....................................................................................1-9
Pulse rate.................................................................................................................................1-9
Range............................................................................................................................1-9
Accuracy.....................................................................................................................1-9
Environmental................................................................................................................... 1-10
Operating................................................................................................................ 1-10
Storage...................................................................................................................... 1-10
Battery packs.................................................................................................................................... 1-10
AA battery pack................................................................................................................ 1-10
Recommended brands.................................................................................... 1-11
NiCd rechargeable battery pack............................................................................. 1-11
Environmental—NiCd and AA................................................................................. 1-11
Operating................................................................................................................ 1-11
Storage...................................................................................................................... 1-11
Precautions....................................................................................................................................................1-12
Warnings............................................................................................................................................ 1-12
Handling............................................................................................................................... 1-12
Failure of operation........................................................................................................ 1-12
Explosion hazard.............................................................................................................. 1-12
Fire hazard.......................................................................................................................... 1-12

Contents
ii
Electrical shock and flammability hazard........................................................ 1-12
Electrical shock hazard................................................................................................ 1-13
Patient safety....................................................................................................................... 1-13
Operator safety.................................................................................................................. 1-13
Sensors................................................................................................................................... 1-13
ata validity........................................................................................................................ 1-13
Cautions.............................................................................................................................................. 1-14
Static sensitivity................................................................................................................ 1-14
Battery packs....................................................................................................................... 1-14
Cleaning................................................................................................................................ 1-14
HP printer............................................................................................................................ 1-14
isposal.................................................................................................................................. 1-14
2/ Troubleshooting
3770 3775 pulse oximeter.....................................................................................................................2-2
Printer..................................................................................................................................................................2-5
Battery charger monitoring station.....................................................................................................2-6
Battery charger (single)..............................................................................................................................2-8
3/ ervice Policy and Repair Procedures
Service policy..................................................................................................................................................3-1
Ordering parts and obtaining service..................................................................................3-1
Packaging and returning equipment....................................................................................3-2
Safety guidelines...........................................................................................................................................3-2
Cleaning procedures...................................................................................................................................3-3
Oximeter, battery packs, and battery chargers...............................................................3-3
Sensors....................................................................................................................................................3-3
Inspecting the oximeter and replacing parts...............................................................................3-4
isassembling the oximeter.......................................................................................................3-4
Replacing parts..................................................................................................................................3-5
Assembling the oximeter.............................................................................................................3-5
Checking normal operation....................................................................................................................3-7
4/Illustrated Parts
Service kits—3770 and 3775 oximeters.........................................................................................4-1
3775 oximeter assembly..........................................................................................................................4-2
3775 assembly parts........................................................................................................................4-2
3775 assembly illustration...........................................................................................................4-3
3770 oximeter assembly..........................................................................................................................4-4
3770 assembly parts........................................................................................................................4-4
3770 assembly illustration...........................................................................................................4-5

1-1
1/Overview
This manual contains instructions for servicing the atex-Ohmeda 3770 and 3775
Pulse Oximeters.
This chapter contains:
• A general description of the oximeter and its functional components.
• Oximeter and battery pack specifications.
• Precautions, including specific warnings and cautions, you must follow when
servicing the oximeter.
Related information
The content of this manual assumes you are familiar with how the unit operates.
For a detailed description of the unit’s components, key functions, and general
operating guidelines, see the Datex-Ohmeda 3770/3775P Pulse Oximeter User’s
Manual. General maintenance procedures contained in that manual, such as how
to replace batteries in the AA battery pack, are not repeated in this manual.
If you need to reference printed circuit board schematics and component lists,
purchase and refer to the information contained in the 3770/3775 PCA rawings
Service Kit, REF 6050-0005-558.
You’ll find detailed instructions for servicing and repairing the battery charger
monitoring station in the Battery Charger M nit ring Stati n Service Manual (REF
6050-0003-861). If you need to replace fuses or change the voltage selection for the
monitoring station, refer to that manual.
Note: The NiCd and AA battery packs, the single-station battery charger, and the
Hewlett-Packard® (HP) printer are not serviceable accessories.
For information on sensor application and cleaning (reusable sensors only), see the
instructions for the sensor.
Technical competence
CAUTION: Only qualified service personnel s ould perform t e procedures described in t is manual.
Only atex-Ohmeda service personnel or competent individuals who are
experienced with servicing medical devices of this nature should perform the
procedures described in this manual.

3770/3775 Pulse Oximeter Service Manual
1-2
General description
Two models of the oximeter are available: the 3770 and the 3775. Both oximeters
operate on power supplied by a battery pack. In addition, either oximeter, when a
nickel-cadmium (NiCd) battery pack is attached, can be positioned in the battery
charger monitoring station and operated using the station’s C (from AC mains)
power supply.
• The 3770 oximeter is designed specifically for spot checking SpO2 and pulse
rate. It has no alarms or user-definable parameters and is not intended for
continuous monitoring.
• The 3775 oximeter is a full-featured model designed for spot checking in
addition to short- and long-term continuous SpO2 and pulse rate monitoring.
This model can print trend data, through an infrared link, to the optional
Hewlett-Packard® (HP) printer.
Note: Throughout this manual, components and features available on both
oximeter models and those found only on the 3775 oximeter are discussed. If you
are working on the 3770, references to components specific to the 3775 do not
apply.
Theory of operation
The oximeter uses a two-wavelength pulsatile system—red and infrared light—to
distinguish between oxygenated (O2Hb) and reduced (HHb) hemoglobin, each of
which absorbs different amounts of light emitted from the oximeter sensor. The
system then calculates the relative percentage of these two constituents and SpO2.
Time
Variable absorption
(Due to arterial pulse)
Arterial blood absorption
Venous blood absorption
Ot er tissue absorption
Absorption
Figure 1-1. ignal composite
Arterial blood pulsation at the test site modulates the transmission of the oximeter
sensor’s light. Since other fluids and tissues present generally don’t pulsate, they
don’t modulate the light passing through that location. The pulsatile portion of the
incoming signal is used to detect and isolate the reduction of light energy due to
arterial blood flow.

1/Overview
1-3
1
0
-1
-2
600 700 800 900 1000
HHb
(Red)
660 nm
(Infrared)
940 nm
O2Hb
Extinction (10x)
Wavelength (nm)
Figure 1-2. Extinction vs. wavelength
The sensor’s photodetector converts the light, which is partially absorbed and
modulated as it passes through the tissue sample, into an electronic signal. Since
O2Hb and HHb allow different amounts of light to reach the photodetector at the
selected wavelengths, the electronic signal varies according to the light source that
is “on” and the oxygenation of the arterial hemoglobin. Analog and digital signal
processing then convert the light-intensity information into SpO2 and pulse rate
values for display on the monitor.
Calibration
atex-Ohmeda pulse oximeters use two wavelength ranges, 650 nm to 665 nm and
930 nm to 950 nm, both with an average power of less than 1 mW. These wavelengths
are used to calculate the presence of oxyhemoglobin (O2Hb) and reduced hemoglobin
(HHb). A CO-oximeter typically uses four or more wavelengths of light and calculates
reduced hemoglobin (HHb), oxyhemoglobin (O2Hb), carboxyhemoglobin (COHb), and
methemoglobin (MetHb). Because of this, pulse oximetry readings and CO-oximetry
readings will differ in situations where a patient’s COHb or MetHb are increased.
Two different methods of calibration are currently used by oximeter manufacturers:
fractional and functional.
• The fractional saturation is determined by dividing the oxyhemoglobin by the
total hemoglobin, represented mathematically as
Fractional SpO
2
= x 100 = x 100
O
2
Hb
Hb
TOTAL
O
2
Hb + HHb + COHb + MetHb
O
2
Hb
i.e., the percentage of the total amount of hemoglobin carrying oxygen.
• The functional saturation is represented mathematically as
Functional SpO2 = x 100 = x 100
O2Hb
HbTOTAL - COHb - MetHb O2Hb + HHb
O2Hb
i.e., the percentage of hemoglobin capable of carrying oxygen that is carrying
oxygen.

3770/3775 Pulse Oximeter Service Manual
1-4
The calculation of SpO2 assumes 1.6% carboxyhemoglobin (COHb), 0.4%
methemoglobin (MetHb), and no other pigments. Appreciable variation from
these values will influence SpO2 accuracy. These values are based on the atex-
Ohmeda Pulse Oximeter Empirical Calibration Study.
The 3700/3775 uses the fracti nal calibration method.
Functional components
Figure 1-3 illustrates the relationship between each functional component.
Sensor
Signal patDigital core
Power supplyOn/Off
Analog boardDigital board
Battery pack/
AC adapter
Return Battery monitor
board
Temperature
Power
Figure 1-3. ystem block diagram
A complete oximetry system requires digital and analog processing. The digital
board provides signal acquisition, numerical processing, and user interface for the
oximeter. The analog board amplifies and conditions the biological signal. The
digital board then samples the conditioned signal, performs the oximetry
algorithm, and displays the results on numeric and graphic LE displays.
The user interface features an eight-character dot-addressable LE display, a
24-segment LE driver, a variable frequency audio driver, and (for the printer
option) an infrared wireless transmitter.

1/Overview
1-5
Digital board
The core processing of the digital board is provided by a 16-bit processor,
nonvolatile FLASH memory, semivolatile SRAM, and a Real Time Clock. For
signal acquisition, it has an A-to- converter (which is internal to the processor),
I/O ports for timing and control, and an 8-bit -to-A converter.
On/Off
Power control
(Reset control)
Address
decode
Programmable
interval
timer (PIT)
Audio tone
generator
Ambient lig t
detection Processor
Real-time
clock I.R.
wireless
transmitter
Rotary encoder
and
pus buttons
Alp anumeric
LED display
Code memory
Data memory
LED driver
(bargrap , low
battery, alarm bar)
Analog board
80-pin
connector
Perip eral
I/O (PPI)
Digital-to-analog
converter (DAC)
Analog
ignal
Path
Timing
Figure 1-4. Digital system block diagram.
80-pin board-to-board connector
The 80-pin board-to-board connector interfaces with the analog board and contains
signals shared by both boards: power supplies, rotary encoder signals, oximetry
timing and control, and many ground connections.

3770/3775 Pulse Oximeter Service Manual
1-6
Analog board
The analog board provides the oximetry analog signal processing, sensor LE
drive, detection of interfering signals, housekeeping and fault monitoring, standby
and operational power, power switching, and battery interface. It also provides
structural support for the digital board and the battery contacts. It contains
attachments for the sensor connector, rotary encoder, and serial port. It also
provides the grounding system for the case shield with EMC capacitors to shunt
high-frequency currents.
>
VCC
UPS
-V
-PROBE
INTDET-
AVG DRV
VREF
LEDDRV
LOBAT
AMUX
INTF
ACA - ACC
VERN
RED
IR
RLT
IRLT
DARK
DLT
PETE
DISABLE
+VSW
REXPULSE
REXCHA
REXCHB
REXPB
OPERATE / TEST
TXD
RXD
GROUND*
DETECTOR
DET RETURN*
IR CATHODS
RED CATHODE
ANODES*
PROBE ID
ID RETURN
VBATT
BATMON
BATTERY RETURN*
GROUND*
GROUND*
REXPULSE
REXCHA
REXCHB
REXPB
SERIAL PORT
Rotary
encoder
Battery
assembly
Sensor
D
I
G
I
T
A
L
B
O
A
R
D
A
N
A
L
O
G
B
O
A
R
D
GROUND
MUX 0-3 , MUX 3- 5
*Essential grounds
>
<
<
<
Figure 1-5. Analog board and digital board system
Note: The rotary encoder is installed on the 3775 analog board only; in all other
respects the 3770 and 3775 analog boards and their components are identical.

1/Overview
1-7
pecifications
Unless otherwise indicated, all specifications are nominal and are subject to
change without notice. Unless otherwise indicated, the specifications below apply
to both oximeters.
Electromagnetic effects
The 3770 or the 3775 when used with a LR6 (AA) battery pack, a NiCd battery
pack, or a NiCd battery pack in a battery charger monitoring station are referred
to as the “system” for EMC purposes.
• Indications that the system is experiencing electromagnetic interference
include:
• Variations in the display (pleth bar does not correlate to physiological signals).
• Sudden increases or decreases in the signal strength indicator that do not
correlate to physiological condition of the patient.
• PROBE? messages that are not resolved by the instructions found in the
3770/3775 Pulse Oximeter User’s Manua.
• T he display of “rolling dots” when a valid physiological signal is present.
This interference may be intermittent and careful correlation between the effect
and its possible source is important. The system will not display any of these
indications if it is used within its intended electromagnetic environment.
Environment
Suitable for use in the environment described in IEC/EN 60601-1-2 (1993).
EMC performance
The system complies with the requirements of IEC/EN 60601-1-2 (Electromagnetic
compatibility - Requirements and tests). The following basic EMC standards were
applied to verify conformance.
Emissi ns: IEC/EN 55011 Group I, Class B (1997)
Immunity: IEC/EN 61000-4-2 (1995), 8 kV air, 3kV contact
IEC/EN 61000-4-3 (1995), 3 V/m
IEC/EN 61000-4-4 (1995), 2 kV power, 1kV I/O
IEC/EN 61000-4-5(1995), 2 kV line to earth, 1 kV line to line
International Electrotechnical Commission (IEC) classifications
The oximeter complies with the requirements of IEC/EN 60601-1 (1988) Part 1:
General requirements for safety of medical electrical equipment:
Degree f pr tecti n against electric sh ck: Type BF applied part
IPX3 Degree f pr tecti n against ingress f liquids:
Sprayproof (IEC/EN 60529)
Type f pr tecti n against electric sh ck: Internally powered equipment/Class II
M de f perati n: Continuous

3770/3775 Pulse Oximeter Service Manual
1-8
Compliance with standards
The presence on the device of any symbol described below indicates compliance
with the standard represented by that symbol.
0197
Medical evice irective 93/42/EEC of the European Union for a
class I (with a measuring function), IIa, IIb, or III device.
Medical electrical equipment classified with respect to electric
shock, fire, and mechanical hazards only, in accordance with the
Canadian Standards Association CAN/CSA C22.2 No. 601.1 (1990).
Medical electrical equipment classified with respect to electric
shock, fire, and mechanical hazards only, in accordance with
Underwriters Laboratories Inc. UL 2601-1 (1994).
Oximeter
Default settings
Each time you power on the oximeter the following system settings are in effect:
• Low-SpO2 alarm limit = 85
• High-SpO2 alarm limit = On
• Alarm volume = On
• Pulse beat volume = Off
• SpO2 averaging interval = 12 seconds
Settings for time, date, and language are retained when the system is powered off
as long as a battery is in place.
General
Visual displays and indicators
The displayed SpO2 and pulse rate values are updated every second. The
plethysmographic waveform sweep is updated every 4 seconds.
Main display: 8-character alpha-numeric; green; variable intensity dependent on
ambient light conditions
Waveform display: 8 green LE s
Signal strength indicator bar: 4 LE s (1 dark green, 1 yellow green, 1 yellow, and
1 orange)
Low battery indicator: 1 orange LE
Alarm bar (3775 only): red
isplay update interval: 0.5 seconds
isplay hold interval: 12 seconds
Dimensions
Height: 18.54 cm (7.3 inches; 9.5 inches including FlexConnect™)
Width: 7.62 cm (3.0 in.)
epth: 5.33 cm (2.1 in.)
Weight: 0.33 kg (9.6 oz.) without battery pack

1/Overview
1-9
Power
Typical consumption: 1.6 W
Typical current: 180 mAmps
Circuitry
Microprocessor controlled
Automatic self-test at power on
Automatic setting of default parameters (3775 only)
Automatic alarm messages
Automatic/continuous system diagnostics
ensor emitter wavelength ranges
Red LE peak wavelength range: 650 to 665 nm
Infrared (IR) LE peak wavelength range: 930 to 950 nm
Average power: ≤ 1 mW
(3775 only) Audio indicators
Alarm volume: On (default) and off
Pulse rate volume: On and off (default)
Pitch modulation to reflect changing SpO2 levels
Alarm silence (120 seconds)
Low- and high-SpO2 out-of-limits alarm
Sensor condition alarms
System failure alarms
p O 2
Range: 0 to 100%
Accuracy (±1 standard deviation)
80 to 100% ± 2%
60 to 79% ± 3%
Below 60% unspecified
Calibration: fractional
Interfering substances
Carboxyhemoglobin may erroneously increase readings. The level of increase is
approximately equal to the amount of carboxyhemoglobin present. yes, or
substances containing dyes, that change usual arterial pigmentation may cause
erroneous readings.
(3775 only) Alarm limits
Low = 60 to 99%
High = 61 to 100% and OFF
Pulse rate
Range 40 to 235 beats per minute
Accuracy ± 1.7% of current reading
(accuracy calculations assume a constant pulse rate)

3770/3775 Pulse Oximeter Service Manual
1-10
Environmental
Operating
Temperature: 0 to 50 ºC (32 to 122 ºF)
Humidity: 0 to 95% RH, noncondensing
Atmospheric pressure: 550 to 1,060 hPa (8 to 15.4 psia)
Vibration: Meets or exceeds:
ASTM 4728, (Method C)
MIL-ST -810E, Method 514.4, Section I.3.4.3
IEC/EN 60068-2-37
rop/shock: Meets or exceeds:
IEC/EN 60068-2-32 (Procedure 1)
MIL-ST 810E, Method 516.4, Section I.3.6
torage
Temperature: –40 to 70 ºC (–40 to 158 ºF)
Humidity: 0 to 95% RH, noncondensing
Atmospheric pressure: 496 to 1,060 hPa (7.2 to 15.4 psia)
Vibration: Meets or exceeds:
ASTM 4728, (Method C)
MIL-ST -810E, Method 514.4, Section I.3.4.3
rop/shock: Meets or exceeds:
IEC/EN 60068-2-32 (Procedure 1)
MIL-ST 810E, Method 516.4, Section I-3.6
Battery packs
The operation time depends on the monitoring technizue (long monitoring cycles
or short, spot-checks).
AA battery pack
Weight: 0.12 kg (4.4 oz.) without cells; 0.26 kg (9.3 oz.) with cells.
Capacity, operation time, charge time, and life cycle depend on the battery cell.
Battery type Life expectancy in hours
Alkaline (8 to 15 ours)
Rec argeable alkaline (2.5 to 8 ours)
Lit ium (10 to 20 ours)
Carbon (2 to 4.5 ours)
05101520
Figure 1-6.
AA battery life cycles

1/Overview
1-11
Low battery indicator LE lights depending on the battery cell, as follows:
Alkaline <2.5 hours
Alkaline rechargeable <1 hour
Carbon <2 hours
Lithium <1 hour
Recommended brands
Alkaline Lithium Carbon
uracell ™ Eveready Eveready
Eveready™ Rayovac
Kodak™
Panasonic™
Rayovac®, including
rechargeable "Renewal®"
Top Crest™
NiCd rechargeable battery pack
Weight: 0.43 kg (12.5 oz.)
Power: 9.6 V, sealed nickel-cadmium (8 cells)
Capacity: 1.4 A-hours
Operation time: 8 hours
Charge time: 2 hours
Life cycle: 1 year (500 cycles)
Low battery indicator LE illuminates when battery usage time is at or below
~15 minutes.
Environmental—NiCd and AA
Operating
Temperature: 0 to 50º C (32 to 122 ºF) – NiCd
0 to 40º C (32 to 104 ºF) – AA
Humidity: 0 to 95% RH, noncondensing
Atmospheric pressure: 550 to 1,060 hPa (8 to 15.4 psia)
Vibration: Meets or exceeds:
ASTM 4728 (Method C)
MIL-ST -810E, Method 514.4, Section I.3.4.3
IEC/EN 60068-2-37
rop/shock: Meets or exceeds:
IEC/EN 60068-2-32 (Procedure 1)
(NiCd) MIL-ST 810E, Method 516.4, Section I-3.6
torage
Temperature: –40 to 50 ºC (–40 to +122 ºF)
Humidity: 0 to 65% RH (±20%) noncondensing
Atmospheric pressure: 496 to 1,060 hPa (7.2 to 15.4 psia)
Vibration: Meets or exceeds:
ASTM 4728 (Method C)
MIL-ST -810E, Method 514.4, Section I.3.4.3
rop: Meets or exceeds:
IEC/EN 60068-2-32 (Procedure 1)

3770/3775 Pulse Oximeter Service Manual
1-12
Precautions
Two types of precautions appear in this manual: warnings and cautions.
• A WARNING indicates a potentially harmful situation that may cause injury to a
patient or operator.
• A CAUTION indicates a condition that may lead to equipment damage or
malfunction.
Read this section fully and carefully before using or servicing the oximeter and its
accessories.
Warnings
Handling
Handle the oximeter and its accessories with care. Improper handling can cause
damage or inaccurate operation of these devices.
Failure of operation
If the oximeter fails to respond as described, do not use it until qualified personnel
have corrected the situation or the unit has been serviced.
Explosion hazard
o not use the oximeter, printer, or battery charger in the presence of flammable
anesthetics or other flammable substances in combination with air, an oxygen-
enriched environment, or nitrous oxide.
Use only a 3770/3775 battery pack as part of the oximeter.
Cadmium is a hazardous substance. o not incinerate or burn a NiCd battery
pack. ispose of a battery pack through an approved hazardous material disposal
facility or by returning it to atex-Ohmeda for reclamation.
Use only a atex-Ohmeda battery charger to recharge or condition a atex-Ohmeda
NiCd battery pack. o not use a atex-Ohmeda battery charger to recharge or
condition a NiCd battery pack that is not made by atex-Ohmeda.
o not expose a battery pack to any temperature that is hotter than you can
tolerate to touch.
Fire hazard
To protect against fire hazard, replace the fuses in the battery charger only with
fuses of the same type and local line voltage rating.
Electrical shock and flammability hazard
Before cleaning or servicing the oximeter, always turn it off.
Before cleaning or servicing the printer, always turn it off and disconnect the
power cord from the AC mains power supply.
Before cleaning or servicing the battery charger, always disconnect the power cord
from the AC mains power supply.

1/Overview
1-13
Electrical shock hazard
To protect yourself from possible electric discharge when the cover of the unit is
removed and the unit is receiving power, avoid contact with internal components.
o not attempt to repair the printer, battery pack, or single-station battery charger.
They are not serviceable parts.
The battery charger must be properly grounded.
• Insert the three-connector plug on the power cord into a three-wire, grounded
hospital-grade receptacle only. If a three-wire receptacle is not available, a
qualified electrician must install one in accordance with the governing
electrical code.
• Never remove the grounding connector from the power plug. The power cord
and plug must be intact and undamaged.
• o not use extension cords or adapters.
Patient safety
Never test or perform maintenance on equipment while it is being used to
monitor a patient.
Operator safety
o not handle hot or leaking battery packs or batteries.
ensors
iscard a damaged sensor immediately. o not repair a damaged sensor or use a
sensor repaired by others.
To prevent injury or equipment damage, use only atex-Ohmeda oximeter sensors
approved for use with this oximeter. For complete information about the safe and
appropriate use of a sensor, consult the instructions for that sensor.
Data validity
To prevent erroneous readings, do not use an inflated blood pressure cuff or
arterial blood pressure measurement device on the same limb as the oximeter
sensor.
Interfering substances, excessive ambient light, excessive motion, low perfusion,
low signal strength, incorrect sensor placement, or electrical interference at the
sensor site can result in the display of inaccurate SpO2 data.

3770/3775 Pulse Oximeter Service Manual
1-14
Cautions
US Federal and Canadian laws restrict this device to sale by or on the order of a
licensed medical practitioner.
Only qualified service personnel should perform the procedures in this manual.
tatic sensitivity
Internal electronic components are susceptible to damage by electrostatic
discharge. To avoid damage when disassembling the monitor, observe the
standard precautions and procedures for handling static-sensitive components.
Battery packs
To prevent battery pack damage,
• Never attempt to take a battery pack apart. Access only the battery
compartment for replacing batteries in the AA battery pack.
• Never attempt to replace a cell in the NiCd battery pack. The set of eight cells
is matched for capacity and improper operation could occur.
• o not put a battery pack where it can be short-circuited by contact with
metal objects, such as in a pocket with keys.
• Use only batteries recommended by atex-Ohmeda in the LR6(AA) battery pack.
Service diagnostic mode is to be used by atex-Ohmeda service personnel only.
Cleaning
o not autoclave, pressure sterilize, or gas sterilize the oximeter, printer, battery
pack, or battery charger.
Use cleaning solution sparingly. o not immerse the oximeter, printer, battery
pack, or battery charger in liquid. Excessive solution can flow into the device and
cause damage to internal components.
When cleaning the display lens, do not use abrasive cleaning compounds or other
materials that could damage the lens.
o not use petroleum-based solutions or solutions containing acetone, ethanol,
freon, trichloroethylene, or harsh solvents to clean the oximeter, printer, battery
pack, battery charger, or the protective covering on these devices. These
substances attack the devices’ materials and device failure may result.
When cleaning reusable oximeter sensors, follow all warnings and cautions stated
in the sensor user instructions.
isposable sensors are intended for single patient use only.
HP printer
To avoid damage to the printer, use only an AC adapter recommended by and
available from atex-Ohmeda.
Disposal
When the oximeter has reached the end of its useful life, dispose of it in
accordance with local procedures and regulations.