Welch Allyn 5002 Series User manual

Welch Allyn Masted Scales
Service Manual
Model 5002 Mobile Stand-On Scale
Model 5122 Stand-On Scale
Model 5702 Mobile Bariatric Scale
Model 6002 Wheelchair Scales
Model 6702/SP/W Mobile Bariatric Scale

© 2016 Welch Allyn. All rights are reserved. To support the intended use of the product described in this
publication, the purchaser of the product is permitted to copy this publication, for internal distribution only,
from the media provided by Welch Allyn. No other use, reproduction, or distribution of this publication, or any
part of it, is permitted without written permission from Welch Allyn. Welch Allyn assumes no responsibility for
any injury to anyone, or for any illegal or improper use of the product, that may result from failure to use this
product in accordance with the instructions, cautions, warnings, or statement of intended use published in this
manual.
Software in this product is Copyright 2016 Welch Allyn or its vendors. All rights are reserved. The
software is protected by United States of America copyright laws and international treaty provisions
applicable worldwide. Under such laws, the licensee is entitled to use the copy of the software incorporated
with this instrument as intended in the operation of the product in which it is embedded. The software may not
be copied, decompiled, reverse-engineered, disassembled, or otherwise reduced to human-perceivable form.
This is not a sale of the software or any copy of the software; all right, title, and ownership of the software
remain with Welch Allyn or its vendors.
For information about any Welch Allyn product, contact your local Welch Allyn representative:
http://www.welchallyn.com/en/other/contact-us.html
DIR 80021524 Ver. D
Revision date: 2018-01
Welch Allyn, Inc.
4341 State Street Road
Skaneateles Falls, NY 13153 USA
www.welchallyn.com
Customer Support
Placing orders, checking on pricing, billing, or repairs
[e-mail]
1.800.535.6663, Option 2, 1, 5
9am - 5pm EST
Mon - Fri

CONTENTS
Scale setup ....................................................................................................................................................4
Enter custom setup mode.........................................................................................................................4
Set the options..........................................................................................................................................4
Enter Advanced Service Mode..................................................................................................................6
Menu List for Advanced Service Mode.....................................................................................................6
Support services............................................................................................................................................7
Warranty...................................................................................................................................................7
Repairs ......................................................................................................................................................8
Returning products ...................................................................................................................................8
Warranty service.......................................................................................................................................9
Non-warranty service................................................................................................................................9
Technical Descriptions ..................................................................................................................................9
Scale Technical Description.......................................................................................................................9
Printer General Description ....................................................................................................................15
Maintenance of Scales................................................................................................................................20
Battery replacement...............................................................................................................................21
Change the printer paper........................................................................................................................21
Calibration of Scale .................................................................................................................................23
Calibration Procedure.............................................................................................................................24
Masted Scales Disassembling Guide...........................................................................................................26
Required tools:........................................................................................................................................26
5002, 6002, 6702, 6702SP, 6702W MAST Disassembling.......................................................................27
5002, 6002, 6702, 6702SP, 6702W Disassembling .................................................................................40
5122 Disassembling ................................................................................................................................51
Troubleshooting .........................................................................................................................................59
Scale Troubleshooting.............................................................................................................................59
Printer Troubleshooting..........................................................................................................................61
Symptoms and solutions.........................................................................................................................63
Repair Parts List ..........................................................................................................................................72
5002/5702/6002 Base Components.......................................................................................................72

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6702/6702W/6702SP Base Components................................................................................................72
6702/6702W Base Components .............................................................................................................72
6702SP Base Components ......................................................................................................................73
5122 Scale Components..........................................................................................................................74
MAST Components for 5002, 5702, 6002, 6702.....................................................................................75
Options....................................................................................................................................................75
Schematics & Part Diagrams.......................................................................................................................76
Scale setup
You can customize the scale to best suit your needs. Configurations that can be selected
include the automatic shut-off time, weighing units, weight resolution, and more.
Enter custom setup mode
1. Make sure the scale is powered down.
2. Press and hold ST while pressing ON.
3. Once the scale powers up, press and release ST five times. The scale displays SEt-UP and produces a series
of four long beeps.
4. The "RE CALL" pushbutton is used to select the particular option value.
5. Once this value is selected the scale can be advanced to the next option by again pressing the “ST”
pushbutton or it can be shut-off by pressing and holding the "ON" pushbutton.
Set the options
Enter the custom setup as described.
1. Press ST to scroll through the custom setup options.
Note Options indicated with an asterisk (*) have multiple selections.
2. Press RE CALL once a value is displayed to change the value. When the desired value appears, press ST to
set the new value.
3. You can exit the menu at any time by pressing ON to power down the scale. The scale saves all changes.
The options displayed with each press are as follows:
Option displayed Feature
SOFt This option displays the software version of your scale.
dAtE This option displays the release date of the software. The format is MM/DD/YY.
SCALE This option displays the model number of the scale.
AutOFF* This displays the number of seconds before the scale turns off. The Cont value prevents the
scale from turning off automatically.
AC con* This option causes the scale to remain on when plugged in to AC power.
rES* This option allows you to change the resolution of weight. Pressing ST switches between the

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following options:
LBS Kg
0.1 0.05
0.1 0.1
0.2 0.1
0.5 0.2
1.0 0.5
UnitS* This option allows you to change the displayed weight unit. Press RECALL to choose between the following
options:
Note Do not change the scale units if you have purchased the kilogram-only option.
KILOS* This option allows the weight to display in kilograms.
POUNDS* This option allows the weight to display in pounds.
bEEPEr* This option determines the audible signal that occurs when a front panel button is pressed.
rECALL* This option allows you to turn ON or OFF the RECALL button functionality.
rS-232 Detailed instructions for this feature are available from Welch Allyn. Go to
http://www.welchallyn.com/en/other/contact-us.html to find your local representative.
OutPut* This option displays the current data port output option. Detailed instructions for this feature are
available from Welch Allyn. Go to http://www.welchallyn.com/en/other/contact-us.html to find
your local representative.
Set the value to OFF to disable the optional internal printer or the RS-232 port.
PrtUnt* This option determines whether pounds or kilograms are displayed on a printout.
If the pounds and kilograms indicators are illuminated on the control panel, the printed output is
determined by whichever unit is selected on the control panel.
If the kilogram indicator is illuminated, it will only print in kilograms, regardless of the unit is
selected on the control panel.
If the pounds’ indicator is illuminated, it will only print in pounds, regardless of the unit is
selected on the control panel.
PrtOPT* Press RECALL to choose between the following options:
PnlPrt: The current weight is printed when PRINT is pressed on the control panel.
AutPrt: The current weight is automatically printed when a weight reading occurs.
bAud* This option allows you to set the baud rate. Values are 1200, 2400, 4800, 9600, and
19200.
pArity* This option allows you to change the parity between the following options:

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Off: No parity, 8 data bits
Odd: Odd parity, 7 data bits
EuEn: Even parity, 7 data bits
StPbit* This option allows you to change the stop bits between the following options:
1 bit: One stop at the end of a word
2 bits: Two stops at the end of a word
rts.cts* This option allows you to turn On or Off the handshaking hardware for serial transmissions.
Prtbtn* This option allows you to turn On or Off the front panel PRINT button.
rtEPrt* This option allows you to turn On or Off the enabling of printing from a remote location by connecting the
receive line to the ground.
PC brd This option displays the model number of the printed circuit board. A second press of ST
displays the revision of the printed circuit board.
SEt-UP This option is displayed when you have cycled through all the options. Press and hold ON to
power down the scale.
Enter Advanced Service Mode
1. To enter the "service" mode start with the scale turned off.
2. Note the small "ST" logo ("ST") located directly above the "RE CALL" pushbutton, and below the “Zero”
pushbutton on the front panel of the readout.
3. This "ST" contains a small hidden pushbutton.
4. Next; press and hold this "Zero" pushbutton on the front panel while turning the power on with the "ON"
pushbutton.
5. As soon as the scale turns on release the "Zero" pushbutton, then quickly press and release "ST" logo
pushbutton 5 times.
6. The scale will display "Srvice" and produce a series of four long beeps.
7. Service mode has now been entered.
8. Pressing the "ST" pushbutton will advance the display to the next item.
9. The scale will exit the service mode automatically after 3 minutes, or shut-off by pressing and holding the
"ON" pushbutton for 3 or 4 seconds.
10. When the scale is turned back on, normal scale operation will resume.
Menu List for Advanced Service Mode
1. “A-d”, and next window on display will show the raw A/D reading. As you press on the Platform the A/D
reading will chance. The weight chance reading should be positive proportionally with the applied weight
in pounds.
2. “tESt”, and the next window will start displaying the display test, Number will show across from 0 to 9 and
repeat w/ DP, from right side to left side.
3. “Pr-OnS” = Power on start-up, next display will show the number of times the “ON” pushbutton has been
depressed.

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4. “Pr-rcl” = Powered by Recall, next display will show the number of times the “RECALL” pushbutton has
powered-up the scale (from an off state).
5. “COUntS” = Weighing Counts, next display will show the number of times a weight reading has been
achieved.
6. “rEcntS” = Reweigh counts, next display will show the number of times “Reweigh” pushbutton has been
depressed.
7. “rECLLS” = recalls, next display will show the number of times the “RECALL” pushbutton has been
depressed.
8. “OFFS” = Turned Off, next display will show the number of times the scale has been turned off by holding
the “ON” pushbutton down.
9. “PrintS” = Prints, next display will show the number of times the “Print” pushbutton has been depressed.
10. “SEtUPS” = set-up mode, next display will show the number of times the unit has entered into the set-up
mode.
11. “SEruES” = service mode, next display will show the number of times the unit has entered into the service
mode.
12. “CALS” = Cal mode, next display will show the number of times the unit has entered into the Cal mode.
Support services
If you have a problem with the device that you cannot resolve, call the Welch Allyn Technical Support Center
nearest you for assistance. A representative will assist you in troubleshooting the problem and will make every
effort to solve the problem over the phone, potentially avoiding an unnecessary return.
Technical support is available 9am-5pm EST.
Welch Allyn offers the following technical support services:
• Telephone support
• Replacement service parts
• Product service
For information on any of these services, go to www.welchallyn.com/en/servicesupport.html.
Warranty
Welch Allyn will warranty the weight scale to be free of defects in material and workmanship and to perform in
accordance with manufacturer specifications for the period of one year from the date of retail purchase.
The warranty period shall start on the date of purchase. The date of purchase is:
the invoiced ship date if the device was purchased directly from Welch Allyn
the date specified during product registration
the date of purchase of the product from a Welch Allyn authorized distributor as documented from a
receipt from said distributor.
This warranty does NOT cover damages caused by misuse or abuse, including but not limited to:
•Failure caused by unauthorized repairs or modifications
•Damage caused by shock or dropping during transportation
•Damage caused by improper use of the power supply
•Failure caused by improper operation not consistent with the instructions stated in
this Directions for use

8
Should this device require maintenance (or replacement at our option) under warranty, contact your local Welch
Allyn representative: http://www.welchallyn.com/en/other/contact-us.html
Repairs
A Welch Allyn Service Center or Authorized Service Provider must perform all repairs on products under warranty
unless you are a properly trained technician.
CAUTION Unauthorized repairs will void the product warranty.
Qualified service personnel or a Welch Allyn Service Center should repair products out of warranty.
If you are advised to return a product to Welch Allyn for repair or routine maintenance, schedule the repair with
the service center nearest you.
Returning products
When returning a product to Welch Allyn for service, ensure that you have the following information:
•Product name, model number, and serial number. This information may be found on
the product and serial number labels.
•A complete return shipping address.
•A contact name and phone number.
•Any special shipping instructions.
•A purchase-order number or credit-card number if the product is not covered by a
warranty.
•A full description of the problem or service request.
1. Obtain an RMA number. Contact Welch Allyn and request.
Note: Welch Allyn does not accept returned products without an RMA.
2. Ship the device to Welch Allyn, observing these packing guidelines:
Remove from the device the battery, all hoses, connectors, cables, sensors, power cords, and other ancillary
products and equipment, except those items that might be associated with the problem.
Dispose of damaged or leaking batteries in an environmentally safe manner consistent with local regulations.
Note: To ensure safe receipt of your device by the service center and to expedite processing and return of the
device to you, thoroughly clean all residue from the device before you ship it to Welch Allyn. For cleaning
requirements, see the Cleaning instruction in the Directions for Use.
Welch Allyn thoroughly cleans all returned devices on receipt, but any device that cannot be adequately cleaned
cannot be repaired.
3. Write the Welch Allyn RMA number with the Welch Allyn address on the outside of the shipping carton.

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Warranty service
All repairs on products under warranty must be performed or approved by Welch Allyn.
Refer all warranty service to Welch Allyn Product Service or another authorized Welch Allyn Service Center.
Obtain a Return Material Authorization (RMA) number for all returns to Welch Allyn Product Service.
CAUTION Unauthorized repairs will void the product warranty.
Non-warranty service
Welch Allyn Product Service Centers and Authorized Service Providers support non-warranty repairs. Contact any
Welch Allyn regional service center for pricing and service options.
Welch Allyn offers modular repair parts for sale to support non-warranty service. This service must be performed
only by qualified end-user biomedical/clinical engineers.
Technical Descriptions
Scale Technical Description
Welch Allyn Scales utilize the latest developments in electronic scales and microcomputer technology to provide
weighing scales, engineered to be easy to use. This section describes the technical aspects of these scales.
LOAD CELL TRANSDUCERS
The function of the load cell transducer is to convert the weight applied to the weighing platform into an electrical
signal for further processing and subsequent display by the readout. Welch Allyn uses proprietarily designed load
cells in most of the scales to optimize performance and reliability. One of three types of load cell transducers may
be used in your Welch Allyn Scale depending on the model number.
MODELS 5002, 5702, 6002
For many years these scales utilized a configuration called a “gauged-plate”. It is a rectangular, flat aluminum plate
with a bending element in each corner. The bending elements are an integral part of the aluminum plate formed by
cutting relief areas in the four corners. Each bending element has two resistive strain gauges bonded to it in order
to form an electrical “half-bridge” configuration. The four bending elements are further interconnected to form an
equivalent “Wheatstone bridge”. Additional compensating resistors are contained with the gauged-plate’s wiring
to correct for temperature effects.
It is called a “gauged-plate” because it is a flat plate with resistive strain gauges installed on beams that have been
machined out in the corners. The beams were mechanically tuned and matched with small files. This is a unique
and special large flat load cell that allowed us to make a very low platform that is easy for unstable patients to step
up on. It has served us well for over 35 years. We then invented the planar wingback bending beam with four strain
gauges (full bridge).
This “gauged-plate” has been replaced in most scales with four discrete planar beam type load cells designed to
accomplish the same performance as the single gauged plate. This was done in order to maintain costs. A further
advantage is that a single load cell may now be replaced if necessary rather than the complete set of four. These

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beams are electronically tuned and matched with precision resistors. Thus it is possible to replace one load cell
without having to recalibrate the scale—another Welch Allyn unique feature.
Use of four bending elements or matched load cells sums the total weight applied to the weighing platform and
produces an accurate result regardless of the patient’s position on the platform.
READOUT ELECTRONICS
The Welch Allyn second generation scales employ the model 23005 computer instrument board and the 22DSDP
display board. NOTE: Different revision levels of these boards may be incorporated in your scale depending on its
manufacturing date. Differences between these boards will be noted in the description where applicable.
Readout electronics consist of the following:
Differential signal amplification.
Additional amplification and signal filtering.
Analog-to-Digital (A/D) converter and Clock circuit.
Battery and support circuitry, voltage regulators, power supplies, etc.
Microcomputer and support circuitry.
Display board.
Printer assembly.
Printer interface board.
Printer controller board.
DIFFERENTIAL SIGNAL AMPLIFICATION
The weight dependent output signal produced by the load cell transducers in the weighing frame is a “differential
signal”, meaning it is the voltage difference between the “+ Signal” and “- Signal” leads. Integrated circuit U4, an
instrumentation amplifier, is used to interface to this differential signal and amplify it.
The output signal from the load cells is applied to the protection network consisting of diodes CR4/CR5/CR6/CR7.
These diodes prevent destructive high voltages caused by static discharges from damaging U4. A high frequency
filter, formed by L1/L2/C9, C10 couples the weight signal to the input of U4. In U4 the differential signal is amplified
by a factor of 100, and converted to a “ground-referenced” voltage for further processing.
Capacitors C16/C17/C24 provide local bypassing of the power supplies used by instrumentation amplifier U4.
Capacitor C18 furnished compensation of U4 by reducing amplification at higher frequencies.
ADDITIONAL AMPLIFICATION AND SIGNAL FILTERING
Components for an optional second gain stage may be added on the printed circuit board. If included, operational
amplifier U5 is used to provide additional gain and signal filtering. U5, together with capacitors C14/C15 and
resistors R17/R18, forms an active low-pass filter. These components help to remove fluctuations in the weight
signal caused by movement of the patient on the scale. U5, like U4, is “chopper-stabilized” to correct internal offset
and drift errors.
Resistors R24/R25 (optional) are used to increase gain; resistors R26/R27 (optional) are used to gain reduction. An
additional low-pass filter stage furnished by resistor R34 and capacitor C23.