OHAUS Navigator Series User manual

SERVICE MANUAL
NavigatorTM Series Scales

TABLE OF CONTENTS
Ohaus Corporation www.ohaus.com i Navigator Series Service Manual
Page No.
1GETTING STARTED 3
1.1 INTRODUCTION 3
1.2 SERVICE FACILITIES 3
1.3 TOOLS AND TEST EQUIPMENT REQUIRED 4
1.4 SPECIFICATIONS 4
1.5 Controls 6
1.6 MENU STRUCTURE 7
1.6.1 User Menu 7
1.6.2 Cal Sub-Menu 7
1.6.3 Setup Sub-Menu 7
1.6.4 Units Menu 8
1.6.5 Sealing access to balance settings 8
1.6.6 Service Menu 9
2DIAGNOSTIC GUIDE 10
2.1 TROUBLESHOOTING 10
2.1.1 General procedures for Troubleshooting 10
2.2 DIAGNOSTIC GUIDE 10
3MAINTENANCE PROCEDURES 12
3.1 PREVENTIVE MAINTENANCE 12
3.2 OPENING THE SCALE 12
3.3 REPLACING THE LOAD CELL 14
3.4 REPLACING THE PRINTED CIRCUIT BOARD AND DISPLAY 16
3.5 REPLACING THE FUNCTION LABEL 17
3.6 DOWN-STOP ADJUSTMENT 17
4TESTING 19
4.1 TEST MASSES REQUIRED 19
4.2 OPERATIONAL TEST 20
4.3 SEGMENT DISPLAY TEST 20
4.4 LOAD CELL TEST USING RAMP 20
4.5 PERFORMANCE TESTS 21
4.5.1 Precision Test 21
4.5.2 Repeatability Test 22
4.5.3 Linearity Test 25
4.5.4 Off-Center Load Test 26
4.5.5 Adjusting Off Center Load 26
5PARTS LISTS & DIAGRAMS 28
5.1 SPARE PARTS NV 29
5.2 SPARE PARTS NVT 31
APPENDIX A. STANDARD CALIBRATION 35
A.1 SPAN CALIBRATION 35
A.2 LINEARITY CALIBRATION 36
APPENDIX B. SERVICE MENU 37
B.1 ENTERING THE SERVICE MENU 37
B.2 RAMP 37
B.3 LINEAR CALIBRATION 37
B.4 SPAN CALIBRATION 38
B.5 GEOGRAPHICAL ADJUSTMENT FACTOR (GEO) 39

TABLE OF CONTENTS
Navigator Series Service Manual ii Ohaus Corporation www.ohaus.com
B.6LFT 40
B.7EXPANDED RESOLUTION (E.PAnd) 40
B.8 RESET 40
APPENDIX C. SERVICE TOOL 41
C.1 HARDWARE AND SOFTWARE SETUP 41
C.2 REPLACE PCB/ CONFIGURING THE SCALE 42
C.3DOWNLOAD SOFTWARE 43
C.4DIAGNOSTICS 45
APPENDIX D. GEOGRAPHICAL ADJUSTMENT VALUES 46

CHAPTER 2 DIAGNOSTIC GUIDE
Navigator Series Service Manual 3Ohaus Corporation www.ohaus.com
1 GETTING STARTED
1.1 INTRODUCTION
This service manual contains the information needed to perform routine maintenance and service
on the Ohaus Navigator Series scales. Familiarity with the scale’s Instruction Manual is assumed.
The contents of this manual are contained in five chapters:
Chapter 1 Getting Started –Contains information on service facilities, tools, specifications, and
the mechanical and electronic functions of the scale.
Chapter 2 Troubleshooting –Contains a diagnostic guide and error code table.
Chapter 3 Maintenance Procedures –Contains preventive maintenance procedures and
disassembly, repair and replacement procedures.
Chapter 4 Testing –Contains a list of required test masses, an operational test, segment display
test, performance tests and adjustments.
Chapter 5 Drawings and Parts Lists –Contains exploded views of Navigator scales identifying
all serviceable components.
Appendix A Standard Calibration –Explains procedures for Standard Calibration, performed
prior to using a scale, and after service.
Appendix B Service Calibration –Describes the Service Menu and sub-menus, which allow
authorized service personnel to perform factory Linearity and Span calibrations (no pre-set limits),
take Ramp readings, adjust the GEO Factor, and use E.PAnd to temporarily increase readability to
at least 1/10th of the standard readability.
Appendix C Service Tool –Used to re-configure the scale after replacing a Printed Circuit Board,
and download the software
Appendix D Geographical Adjustment Values –The chart of scale settings for every
geographical latitude away from the equator (in degrees and minutes) and every elevation above
sea level (in meters or feet).
1.2 SERVICE FACILITIES
To service a scale, the service area should meet the following requirements:
Should be temperature controlled and meet scale specifications for temperature environmental
requirements.
Must be free of vibrations such as fork lift trucks close by, large motors, air currents or drafts
from air conditioning/heating ducts, open windows, people walking by, fans, etc.
Area must be clean and free of excessive dust.
Work surface must be stable and level.
Scale must not be exposed to direct sunlight or radiating heat sources.
Handle all electronic assemblies with appropriate Electro-Static protection.

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1.3 TOOLS AND TEST EQUIPMENT REQUIRED
1. Common hand tools are sufficient to disassemble the Navigator scales.
2. RS233 Interface Kit –PN 83032107
3. USB Interface Kit –PN 83032108
1.4 SPECIFICATIONS
Specifications for the Ohaus Navigator Scales are listed in Table 1-1. When a scale has been
serviced, it must meet the specifications listed in the table. Before servicing the scale, determine
what specifications are not met.
Special Note regarding Approved scales
The specifications for the approved scales below are only for initial testing. These scales must be
tested according to the requirements of the local Weights and Measures authority. Before returning
the scale to service an approved representative of the local Weights and Measures authority must
certify the scale. Ohaus does not generally recommend the repair of an approved scale that
involves replacement of the load cell or PCB.
TABLE 1-1 SPECIFICATIONS
Non-Approved Models:
Model*
Capacity
Readability
(d)
Repeatabilit
y (Std. Dev.)
Linearity
Span Cal.
Wt.
Lin. Cal.
Wt.
NV222
220g
0.01g
1d
±2d
200g
100g, 200g
NV422
420g
0.01g
2d
±2d
200g
200g, 400g
NV622
620g
0.01g
2d
±2d
300g
300g, 600g
NV221
220g
0.1g
1d
±2d
200g
100g, 200g
NV621
620g
0.1g
1d
±2d
300g
300g, 600g
NV1201
1200g
0.1g
1d
±2d
500g
500g, 1kg
NV2201
2200g
0.1g
1d
±2d
1kg
1kg, 2kg
NVT2201
2200g
0.1g
1d
±2d
1kg
1kg, 2kg
NVT4201
4200g
0.1g
2d
±2d
2kg
2kg, 4kg
NVT6201
6200g
0.1g
2d
±2d
5kg
3kg, 6kg
NVT2200
2200g
1g
1d
±2d
1kg
1kg, 2kg
NVT6200
6200g
1g
1d
±2d
5kg
3kg, 6kg
NVT12000
12000g
1g
1d
±2d
5kg
5kg, 10kg
NVT22000
22000g
1g
1d
±2d
10kg
10kg, 20kg

CHAPTER 2 DIAGNOSTIC GUIDE
Navigator Series Service Manual 5Ohaus Corporation www.ohaus.com
Model*
(NVHD)
Capacity
Readability
(d)
Repeatabilit
y (Std. Dev.)
Linearity
Span Cal.
Wt.
Lin. Cal.
Wt.
NV123
120
0.001
2d
±9d
100g
50g,100g
NV223
220
0.001
2d
±9d
200g
100g,200g
NV323
320
0.001
2d
±9d
300g
150g,300g
NV1202
1200
0.01
2d
±6d
1kg
500g,1kg
NV2202
2200
0.01
2d
±6d
2kg
1kg,2kg
NV3202
3200
0.01
2d
±6d
3kg
1.5kg,3kg
NVT10201
10200
0.1
2d
±4d
5kg
5kg,10kg
Approved Models:
Model*
Max
e
Approval
Class
Span
Cal. Wt.
Lin. Cal.
Wt.
NVT1601M
1600g
0.5g
III
1kg
1kg,1.5kg
NVT3200M
3200g
1g
III
2kg
2kg, 3kg
NVT6400M
6400g
2g
III
5kg
3kg, 6kg
NVT16000M
16000g
5g
III
10kg
10kg, 15kg

CHAPTER 2 DIAGNOSTIC GUIDE
Ohaus Corporation www.ohaus.com 6 Navigator Series Service Manual
1.5 Controls
This section contains information on the basic operation of the scale.
TABLE 1-3 FUNCTIONS OF DISPLAY CONTROLS
Button
Functions
Zero
Yes
Short Press (when on): Sets display to zero
(when off): Turns balance on
Long Press (when on): Turns the balance off
Short Press (in Menu): Selects/accepts displayed setting
Print
Units
No
Short Press: See Interface Manual for operation
description.
Long Press: Toggles through active units
Short Press (in Menu): Toggles through available settings
Function
Mode
Back
Short Press: Selects function setting
Long Press: Selects active Mode
Short Press (in Menu): returns to previous settings
Tare
Menu-Cal
Exit
Short Press: Enter / clear a Tare value
Long Press: Enters User Menu
Short Press (in Menu): Quickly exit User Menu
IR Sensor *
IR Sensors can be programmed to act as a “touchless”
button. See the User Menu section 4.3 for the available
settings.
The IR Sensors can be activated by a hand or other object that is placed about 12mm (½ inch)
above the sensor location. The sensor activation distance will vary based on the reflective nature of
the object. If unwanted activations occur due to unique situations the sensor can be turned off.
*Availability of IR Sensor is dependent on model and region.

CHAPTER 2 DIAGNOSTIC GUIDE
Navigator Series Service Manual 7Ohaus Corporation www.ohaus.com
1.6 MENU STRUCTURE
Programmable features of the Navigator are contained in the User Menu and Service Menu which
are accessed through the Display Panel’s control switches. The menu structures are illustrated
below.
1.6.1 User Menu
The User Menu is easily accessed and documented for the scale operator. For more detail on
using the menu, see the Navigator Instruction Manual.
TABLE 1-5 NAVIGATOR USER MENU STRUCTURE
Sub-Menus:
.C.a.l.
.S.e.t.u.p.*
.M.o.d.e.
.U.n.i.t.*
.E.n.d.
Menu Items:
Span
Lin
End
b.light
A-OFF
IR
Filter
AZT
Stab
Stab.C
End
Count
Percnt
Check
End
g
kg
…
End
* Note: Available settings vary by models and regions
**Availability of IR Sensor is dependent on model and region.
Press and hold Menu until[mMeNU](Menu) is displayed. When released the first sub-menu [.C.a.l.]
(Cal) will be shown.
Press Yesto enter the displayed sub-menu or press No to advance to the next.
Selecting a sub-menu will display the first menu item. Press Yes to view the menu item setting or
press No to move to the next menu item. When viewing the setting, press Yes to accept the setting,
or press No to change the setting. When[End]is displayed, press Yes to return to the sub-menu
selections or No to return to the first item in the current menu.
1.6.2 Cal Sub-Menu
Span[SpaN] (yes, no) - Initiates a span calibration procedure (zero and span). A span calibration
is important when initially setting up the balance.
Lin[Lin] (yes, no) - Initiates a linearity calibration procedure (zero, mid-point and span).
1.6.3 Setup Sub-Menu
Back Light [b.light] (on,off,Auto)-When Back light is set to "on" the balance will always "on".
When Back light is set to "Auto" the balance will turn on when a button is pressed or the
display weight changes.
Auto Off [A-Off] (on, off) - When Auto Off is set to “on” the balance will turn off automatically
after 5 minutes of inactivity. Auto off is used to save battery power.
IR Sensor [Ir.Func] (Off, Tare, Function, Print, Zero, Display) - These settings determine the role
of the IR Sensor. “Zero”, “Print”, “Function” or “Tare” allows the IR sensor to act the same as
the related button. “Display” activates the display if Display-Auto is set. “Off” disables the
sensor.*

CHAPTER 2 DIAGNOSTIC GUIDE
Ohaus Corporation www.ohaus.com 8 Navigator Series Service Manual
Filter [filter] (L1,L2,L3,L4 ) –set the amount of signal filtering
L1———————————>L4
Stability less——————— > greater
Stabilization time faster——— >slower
Auto Zero Tracking[AZT] (OFF,0.5d,1d,3d,5d,8d,10d) –Set the automatic zero tracking
functionality. The display will maintain zero until a change of "0.5d,1d,3d,5d,8d,10d" divisions
per second has been exceeded.
Stable [Stab] (0.5d,1d,2d,5d) –Set the amount of the reading can vary while the stability symbol
remains on.
Stable Compensation [Stab.C] (on, off) - Set the automatic stable tracking functionality. Set it
"off" for dosing or filling application.
Note: Bold always represents factory default Value
*Availability of IR Sensor is dependent on model and region.
1.6.4 Units Menu
This sub-menu activates units so they will be accessible with the Units button. The units in the menu
must be turned “on” to be active.
Note: Available units and modes vary by model and local regulations.
1.6.5 Sealing access to balance settings
The Menu Lock switch limits changes to the Cal, Setup, Mode and Unit menus. The switch in type
approved models may set some balance settings as required by the approval agency. The switch may
be secured using paper seals, wire seals or plastic ties.
Locked
Unlocked

CHAPTER 2 DIAGNOSTIC GUIDE
Navigator Series Service Manual 9Ohaus Corporation www.ohaus.com
1.6.6Service Menu
The Service Menu is intended for use by service personnel. The menu items are generally used
when servicing the scale but there are setting that may be changed to satisfy a customer’s special
requirements. For more detail on using the service menu see Appendix B.
TABLE 1-6 NAVIGATOR SERVICE MENU STRUCTURE
Service Menu
Menu Items:
Ramp
Lin
Span
Geo
LFT
Expand
Reset
End

CHAPTER 2 DIAGNOSTIC GUIDE
Ohaus Corporation www.ohaus.com 10 Navigator Series Service Manual
2 DIAGNOSTIC GUIDE
This section of the manual contains troubleshooting information. Information is contained to isolate
specific problems using Table 2-1, Diagnostic Guide. Follow all directions step by step. Make certain
that the work area is clean. Handle scale components with care. Use appropriate electro-static
protection devices to prevent damage to the sensitive electronic components.
2.1 TROUBLESHOOTING
2.1.1General procedures for Troubleshooting
1. Do the most obvious, user-level remedies.
2. Visual Check:
- Check that the internal parts are clean and free from debris.
- Examine the scale for damage or signs of abuse, replace any damaged items.
- Examine the load cell for signs of bending, twisting or corrosion.
- Check the overload stops, adjust if necessary. (see Section 3.6)
3. Use the error code table for solutions for specific codes.
4. Use the Diagnostic Guide; locate the symptom then follow the suggested remedies in order.
2.2 DIAGNOSTIC GUIDE
Table 2-1 is a Diagnostic Guide designed to help locate the problem area quickly and easily. The
probable causes are listed with the most common cause first. If the first remedy does not fix the
problem, proceed to the next remedy. Before attempting to repair the scale, read all chapters of this
manual to be familiar with the scale components and operation.
Diagnosis:
1. Isolate and identify the symptom.
2. Refer to Table 2-1, Diagnostic Guide and locate the symptom.
3. Follow the suggested remedies in the order they appear.
4. Perform the indicated checks, or see the appropriate section of the manual.
5. Repair or replace the defective section of the scale.
NOTE:
If more than one symptom is observed, approach one area at a time, and remember that
the symptoms may be interrelated. If a problem arises that is not covered in this manual,
contact Ohaus Corporation for further information.

CHAPTER 2 DIAGNOSTIC GUIDE
Navigator Series Service Manual 11 Ohaus Corporation www.ohaus.com
TABLE 2-1. DIAGNOSTIC GUIDE
Symptom
Possible Cause
Remedy
Cannot turn on
No power to balance
Verify connections and
voltage
Poor accuracy
Improper calibration
Unstable environment
Perform calibration
Move balance to suitable
location
Cannot calibrate
Unstable environment
Incorrect calibration
weight
Move the balance to suitable
location
Use correct calibration weight
Cannot access
mode
Mode not enabled
Enter menu and enable mode
Cannot access
unit
Unit not enabled
Enter menu and enable unit
Lo ref
Reference weight is too
low
Increase reference weight.
ref err
Parts counting–sample
weight <1d.
Shows error - exits mode or
goes to [Clr.ApU]
Err 3.0
Incorrect calibration
weight
See section 2.5 for correct
weights
Err 4.4
RS232 buffer is full
Set Handshake on, see
Interface User Manual.
Err 8.1
Power on zero range
exceeded
Clear pan, check Shipping
Lock setting
Err 8.2
Power on zero under
range
Install pan, check Shipping
Lock setting
Err 8.3
Overload (>cap+9e)
Load exceeds balance
maximum capacity
Err 8.4
Under load
Reading below min. range -
Re-install pan.
Err 8.6
Displayed value >999999
Result exceeds display
capability
Err 9
Internal data error
Contact an authorized service
agent
Err 9.1
Calibration data lose
Implement service calibration
Err 9.2
Load cell connection with
PCBA is not good
Re-connect the cable
between load cell and main
PCBA, and then do the
service calibration
Err 9.3
EEPROM data error
Implement service calibration
Err 13
Fail to write EEPROM.
Contact an authorized
service agent
Err 53
Invalid checksum data
Contact an authorized
service agent

CHAPTER 3 MAINTENANCE PROCEDURES
Ohaus Corporation www.ohaus.com 12 Navigator Series Service Manual
3 MAINTENANCE PROCEDURES
3.1 PREVENTIVE MAINTENANCE
Ohaus scales are precision instruments and should be carefully handled, stored in a clean, dry,
dust-free area, and cleaned periodically. Follow these precautionary steps:
–When a scale has had chemicals or liquids spilled on it, all exterior surfaces should be cleaned
as soon as possible with warm water on a damp cloth.
–Do not leave a mass on the scale when the scale is not in use.
–Allow time for the scale to stabilize after moving it from an area which is at a different
temperature than the area where it is to be operated. Allow one hour for each 5°F (2.7°C)
temperature change before using the scale. After temperature stabilization, allow an additional
20 minutes after turning the scale on, for the scale electronics to stabilize.
Preventive Maintenance Checklist
The scale should be inspected and checked regularly, as follows:
1. Remove the Pan and Sub Pan to inspect and clean the area beneath the Pan.
2. Clean the outside of the scale using a damp cloth with warm water.
CAUTION
DO NOT USE CHEMICAL CLEANERS OR SOLVENTS OF ANY TYPE.
SOME CLEANERS ARE ABRASIVE AND MAY AFFECT THE SCALE’S FINISH.
3. Check the Power Cord for broken or damaged insulation.
4. If using batteries and the scale malfunctions, first replace the batteries to see if this resolves the
problem. To isolate a problem with the rechargeable battery option kit, the scale can be
converted back to standard alkaline batteries (see Rechargeable Battery Option User Manual).
5. Make a visual inspection for faulty connectors, wiring, and loose hardware.
3.2 OPENING THE SCALE
Opening the Navigator scale varies slightly according to the specific model, as detailed below. Use
these procedures in order to replace the Load Cell, the Printed Circuit Board or other components.
Opening Navigator Models
Common hand tools are sufficient to disassemble the Navigator scales. Turn the scale off and
unplug the power cord before you begin. Remove any installed batteries. On models with the
Rechargeable Battery Option installed, the battery and the Recharge PCB must be removed. See
the Rechargeable Battery Option Kit instructions for additional information.
1. Remove the stainless steel Weigh Pan.
2. Remove the conductive rubber cap over the Pan Support Screws.

CHAPTER 3 MAINTENANCE PROCEDURES
Navigator Series Service Manual 13 Ohaus Corporation www.ohaus.com
NV Models
NVT Models
Figure 3-1 Pan Support Conductive Rubber Caps.
3. Remove the Pan Support by removing the two screws shown in Figure 3-1.
4. Remove the 5 screws holding the Top and Bottom Housings in place. (See Figure 3-2.)
(Note: NV model shown)
Figure 3-2 Separating the Top and Bottom Housings
5 Turn the scale over and remove the upper housing.

CHAPTER 3 MAINTENANCE PROCEDURES
Ohaus Corporation www.ohaus.com 14 Navigator Series Service Manual
3.3 REPLACING THE LOAD CELL
The Load Cell may need to be replaced because of scale instability, or because the scale does not
calibrate or repeat, or because it is physically broken or displays an error code.
Disassembly:
1. Open the scale –see Section 3.2. Verify that there is no mechanical interference, pinched wire
or bad solder connection that may be causing the load cell to appear defective.
2. Remove the Load Cell –turn the scale over, holding the Load Cell by hand, and remove the 2
load cell screws from the bottom housing. The NV model uses cross-recess screw heads (Phillips
type) while the NVT use hex socket head screws.
3. Turn the scale back on its feet and gently lift off the Load Cell, the attached PCB and the AC
Adapter cable. Place the Load cell and the PCB on a static protected work area.
4. The load cell connection is a five-wire cable that is soldered directly to the PCB. Before
disconnecting the cable record the wire colors and their location on the PCB. (Hint: A digital picture
is an easy and reliable record.) Disconnect the cable connecting the PCB to the Load Cell by un-
soldering the 5 wires from the PCB. Take care not to over heat the PCB which will damage the thin
PCB conductors.
Re-Assembly:
1. Re-solder the new load cell to the PCB, connection J3.
NOTE: The spare part Load Cell may not have the same wire color identifications as the original
load cell. It is necessary to identify the wires from the table below.
J3 has 5 solder pads with the following connections; GND, -EXE, -SIG, +SIG, +EXE.
TABLE 3-1. Load Cell Wire Color Identification
Spare Part Load Cell
Wire Color Identification
NV Models
GND Green thick wire
-EXE Black wire
-SIG White wire
+SIG Green wire
+EXE Red wire
NVT Models
GND Yellow wire
-EXE Black wire
-SIG White wire
+SIG Green wire
+EXE Red wire
NVT Approve Models
GND Yellow wire
-EXE Black wire
-SIG Red wire
+SIG White wire
+EXE Green wire

CHAPTER 3 MAINTENANCE PROCEDURES
Navigator Series Service Manual 15 Ohaus Corporation www.ohaus.com
NV models NVT models NVT Approve models
Figure 3-3 Load cell connections, J3
2. NV models require a load cell spacer to be positioned between the load cell and the Base.
Position the load cell back into the lower housing. Turn the scale over to install the (2) load cell
screws. Loosely tighten the screws so that the load cell can be aligned in the housing. While holding
the load cell, fully tighten the screws. The screws should be tight enough so that the load cell does
not move when pushed from the side. Verify that the load cell is centrally located between the ribs.
3. Turn the scale over onto its feet. Position the PCB on to its locating pins. Coil the excess load
cell cable in front of the load cell.
4. Slide the AC jack into its position in the lower housing. Route the AC adapter cable as shown in
Figure 3-4.
NV models
Route wires
Position jack
Position PCB on
locating Pins

CHAPTER 3 MAINTENANCE PROCEDURES
Ohaus Corporation www.ohaus.com 16 Navigator Series Service Manual
NVT models
Figure 3-4 Position load cell, PCB and AC wires
5. To assemble the Housing, follow the steps in Section 3.2.1 in reverse order.
3.4 REPLACING THE PRINTED CIRCUIT BOARD AND DISPLAY
1. Open the scale –see Section 3.2.
2. Pick the PCB off its mounting pins and position the PCB upside-down so that the load cell wire
connection is easy to access.
3. Disconnect the Load Cell cable from the PCB. The load cell connection is a five-wire cable
that is soldered directly to the PCB. Before disconnecting the cable record the wire colors and
their location on the PCB. (Hint: A digital picture is an easy and reliable record.) Disconnect
the cable connecting the PCB to the Load Cell by un-soldering the 5 wires from the PCB.
Take care not to over heat the PCB which will damage the thin PCB conductors.
4. Unsolder the AC Cable wires from the PCB.
5. Follow these steps in reverse order to install the new PCB.
6. Configure the Scale. (See Appendix C.)
Note: The PCB and the LCD Display are supplied as a single unit. However, if only the LCD
Display needs replacement, it can be separated from the PCB by unsoldering the fine lead-wires
connecting it to the PCB. When installing the new LCD Display, carefully feed the lead-wires
through their holes, check that the new assembly is seated properly on the PCB and then solder the
lead-wires.
Position jack
Position PCB on
locating Pins
Route wires

CHAPTER 3 MAINTENANCE PROCEDURES
Navigator Series Service Manual 17 Ohaus Corporation www.ohaus.com
3.5 REPLACING THE FUNCTION LABEL
The Function Label may need to be replaced. (See Chapter 5 for parts information.) Use a broad
blade, such as a wide X-Acto™knife, to remove the label. Clean the glue residue from the Housing
surface. Then carefully place the new label where the old one was. (See Figure 3-5.)
Figure 3-5. Function Label Removal
3.6 DOWN-STOP ADJUSTMENT
The purpose of the down-stops is to protect the load cell from physical damage. The down-stops are
created by contacting bosses in the Base and adjustment screws or bosses in the Sub-Pan. The NV
models have 3 down-stops, left, right and center near the load cell attachment to the Sub-Pan. The
NVT models have 5 down-stops, left-front, left-rear, right-front, right-rear and center near the load
cell attachment to the Sub-Pan.
NV models with capacity greater than 2kg and NVT models with a capacity greater than 10kg do not
have adjustable down-stops. The down-stop bosses on the Sub-pan are designed to be at the
correct distance to protect these load cells. The smaller capacity load cells require the down-stop
clearance to be decreased for proper load cell protection. Adjustment screws are placed in the Sub-
pan down-stop bosses to reduce the clearance, see figure 3-6.
NV Models
NVT Models
Figure3-6. Down Stop Adjustment Screws
To adjust the down-stops on the applicable models follow the procedures below. Models without
adjustable down-stops need no action.
To ensure full weight reading:
Function Label

CHAPTER 3 MAINTENANCE PROCEDURES
Ohaus Corporation www.ohaus.com 18 Navigator Series Service Manual
The proper down-stop adjustment will allow full weight reading provided the center of the mass is
less than ½ the distance from the pan center to the pan edge. To allow for tolerance this adjustment
is being done at 120% of scale capacity or at scale capacity but ¾ of the distance to the pan edge.
To protect the load cell:
To protect the load cell from physical damage the down-stops should touch at about 200% of scale
capacity. Again to allow for adjusting tolerance the adjustment is made using a 150% weight.
The adjustment screws in the Sub-Pan can be adjusted with a #2 cross-recess (Phillips) screw
driver. Each adjustment screw should contact the Base when 120% to 150% of the scale capacity is
placed in the center of the 4 quadrants of the scale. The Top Housing must be removed to visually
check if the down-stops are touching. Turn the adjustment screw counterclockwise to increase the
clearance and clockwise to decrease the clearance.
An easy method to check the down-stop adjustment is to use the scales weight reading to detect if
the down-stop is touching. This method can only check if the down-stop is set too close preventing
accurate weighing.
1. Place 100% scale’s capacity in the center of the Pan.
2. Note the reading.
3. Move the mass ¾ of the way (between the center and the edge) to the front of the Pan.
Note any significant difference in the displayed weight reading.
4. Repeat the test for the back, left, and right position of the Pan.
5. If there was a weight reading change turn the adjustment screw nearest the quadrant
counterclockwise ¼ turn. Repeat the test to see if it is corrected.
6. If the weight is placed at the edges of the pan there may be a weight change which indicates
the down-stop is working and this is okay.