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OHAUS CKW-55 Service Manual

OHAUS CKW-55 Service Manual

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CKW-55 INDICATOR
SERVICE MANUAL
Ohaus Corporation 19A Chapin Road, P.O. Box 2033, Pine Brook, NJ 07058 (973) 377-9000

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Summary of Contents for OHAUS CKW-55

  • Page 1 CKW-55 INDICATOR SERVICE MANUAL Ohaus Corporation 19A Chapin Road, P.O. Box 2033, Pine Brook, NJ 07058 (973) 377-9000...
  • Page 3 CKW-55 Indicator The information contained in this manual is believed to be accurate at the time of publication, but Ohaus Corporation assumes no liability arising from the use or misuse of this material. Reproduction of this material is strictly prohibited.

  • Page 5: Table Of Contents

    Diagnosis ......................2-1 Basic Examination ....................2-1 Preliminary Checks ....................2-1 Troubleshooting Tables ..................2-1 Error Code Table ....................2-6 CHAPTER 3 CKW-55 INDICATOR TESTING Indicator Testing ....................3-1 Membrane Switch Testing ..................3-1 Main PC Board Testing ..................3-3 3.2.1 Voltage Measurements ................
  • Page 6 TABLE OF CONTENTS (Cont.) CHAPTER 3 CKW-55 INDICATOR TESTING (Cont.) 3.10 Specifications ....................3-25 3.11 Calibration using an External Base ..............3-26 3.12 Calibration3-28 3.12.1 Span Calibration ................... 3-27 3.12.2 Linearity Calibration ................3-28 3.14.3 Calibration Test ..................3-29 3.13 Geographical Adjustment Factor ................3-30 3.14 Calibration Verification using Load Cell Simulator ...........
  • Page 7 Specifications ....................3-25 Geographical Adjustment Values ................. 3-31 Load Cell Output Readings for CKW Bases ............3-34 CKW-55 Indicator Parts List .................. 5-3 CKW-55 Column Parts List ................... 5-4 Service Mode Commands ..................A-1 ASCII Number to Character Conversion ..............A-2...
  • Page 8 3-13 Open and Shorted Jumpers ................3-28 3-14 Main Printed Circuit Board Connections ..............3-32 3-15 Open and Shorted Jumpers ................3-32 RTC Battery Removal/Installation ................4-6 Exploded View of CKW-55 Indicator............... 5-2 Exploded View of CKW Column ................5-4...

  • Page 9: Chapter 1 Introduction

    This service manual contains instructions for the diagnosis and repair work to be performed by qualified Ohaus service technicians or Ohaus authorized service centers. Knowledge of the operation of the CKW- 55 Indicator is assumed. Instruction manuals may be required with this service manual. For complete information on operation, refer to the CKW-55 Indicator and CKW Series Scale Instruction Manual.

  • Page 10: Tools And Equipment

    The calibration masses required is dependent on the capacity and readability of the base used. The masses required to test the CKW-55 Indicator when connected to an Ohaus CKW base must meet the requirements of ASTM Class 4 or OIML F2. The mass values are listed in Table 1-1.

  • Page 11: Service Strategy

    CHAPTER 1 INTRODUCTION 1.4 SERVICE STRATEGY The repair method for the CKW-55 Indicator is the direct replacement of major assemblies. The CKW-55 Indicator contains the following replaceable assemblies: Cover Assembly with Membrane Switch, Main PC Board with LED and Bar Displays, and Power Supply PCB. Optional assemblies consist of: NiMH Rechargeable Battery, Battery Recharge PCB, RS422/485 Communication PCB, and an AC or DC Relay Board.
  • Page 12 CHAPTER 1 INTRODUCTION...

  • Page 13: Chapter 2 Diagnosis

    CHAPTER 2 DIAGNOSIS 2. DIAGNOSIS This section contains information needed to properly evaluate the reported problem and diagnose its cause. 2.1 BASIC EXAMINATION Set up the Indicator according to the Instruction manual. Allow the Indicator to stabilize to room temperature. Examine the Indicator for signs of corrosion or physical damage. 2.2 PRELIMINARY CHECKS Connect the Indicator’s power cord to a suitable AC power source.
  • Page 14 CHAPTER 2 DIAGNOSIS 2-1 INDICATOR WILL NOT TURN ON WITH AC POWER (Cont.) PROBABLE CAUSE REMEDY SYMPTOM Refer to section 3.3 and test the Power Power Supply defective. Indicator will not turn on with Supply. Replace if necessary. See Re- AC Power supply connected pair Procedure 4.4.
  • Page 15 CHAPTER 2 DIAGNOSIS TABLE 2-2 INDICATOR WILL NOT TURN ON USING BATTERY POWER (OPTIONAL)(Cont.). PROBABLE CAUSE REMEDY SYMPTOM Main PC Board is defective. The Main PC Board should be tested in Indicator will not turn on using accordance with section 3.2. The Main battery power (Cont.).
  • Page 16 CHAPTER 2 DIAGNOSIS TABLE 2-5 RS232 COMMUNICATIONS FAILURE. SYMPTOM PROBABLE CAUSE REMEDY Cannot communicate using Menu settings improperly set. Refer to the Instruction Manual and RS232. check the menu settings. Test the RS232 communications, see section 3.7.2. Main PC board defective. If communications cannot be estab- lished, the Main PC Board should be tested in accordance with section 3.2.
  • Page 17 CHAPTER 2 DIAGNOSIS TABLE 2-7 RELAY OPERATION FAILURE (OPTIONAL BOARD) (Cont.). REMEDY PROBABLE CAUSE SYMPTOM The Main PC Board should be tested in Main PC Board defective. Relay functions not working accordance with section 3.2. The Main (Cont.). PC Board if defective should be re- placed.

  • Page 18: Error Code Table

    CHAPTER 2 DIAGNOSIS 2.4 ERROR CODE TABLE The CKW-55 Indicator is equipped with software which will display an error code under certain conditions. Review the listed codes and follow instructions to correct the problem. TABLE 2-10. ERROR CODES SYMPTOM PROBABLE CAUSE...
  • Page 19 CHAPTER 2 DIAGNOSIS TABLE 2-10. ERROR CODES (Cont.) SYMPTOM PROBABLE CAUSE REMEDY Lo bAt Battery is discharged. Connect Indicator to AC power and al- low battery to charge. Battery is defective. Refer to section 3.4 and test the battery. Replace if necessary. See Repair Proce- dure 4.8.
  • Page 20 CHAPTER 2 DIAGNOSIS...

  • Page 21: Indicator Testing

    This section of the manual contains testing procedures of the individual replaceable assemblies of the CKW-55 Indicator. Before and after servicing the CKW-55 Indicator, an operational test and various performance tests should be made to ensure the Indicator meets all specifications.

  • Page 22: Membrane Switch Continuity Test

    CHAPTER 3 INDICATOR TESTING PINS MEMBRANE SWITCH CONNECTOR Figure 3-1. Scale Membrane Switch Wiring Diagram. TABLE 3-1. MEMBRANE SWITCH CONTINUITY TEST FUNCTION SWITCH MEASURE ACROSS PINS LIBRARY 2 & 11 NEXT +/- 2 & 10 TARGET 3 & 10 ON/ZERO 8 &...

  • Page 23: Main Pc Board Testing

    CHAPTER 3 INDICATOR TESTING 3.2 MAIN PC BOARD TESTING The Main PC Board can be tested by measuring voltages on various components. If defective components are found, the entire PCB should be replaced. The following tests are made when it is suspected that the Main PC Board is defective.

  • Page 24: Interconnection Diagram

    CHAPTER 3 INDICATOR TESTING 3.2.1 Voltage Measurements (Cont.) 5. Using a DVM, measure the power supply voltage across pins 1 and 3 of J5, location A in Figure 3-3, it should be 12 volts dc, +0.24V dc. This is the power source for the Main PC board and is regulated.

  • Page 25: Component Layout Diagram

    CHAPTER 3 INDICATOR TESTING 3.2.1 Voltage Measurements (Cont.) Figure 3-3. Component Layout Diagram. 6. Measure the voltage at transistor Q1, pin 2 (location B), it should be 12 V dc, +0.24 V dc. If this voltage is not present, the Main PB Board must be replaced. Refer to section 4.3 and replace the Main PC Board.

  • Page 26: Simulator Testing

    CHAPTER 3 INDICATOR TESTING 3.2.2 Simulator Testing To perform these tests, the use of a load cell Simulator is required. The basic function of a Simulator is to simulate the output of a full bridge load cell allowing the CKW Indicator to be separated from the Base for the purposes of troubleshooting.

  • Page 27: Power Supply Testing

    CHAPTER 3 INDICATOR TESTING 3.3 POWER SUPPLY TESTING The Power Supply Board is located in the Rear Housing. A replaceable fuse is located on the board. This test is made when the Indicator fails to turn on when the power source is on and the indicator is plugged WARNING HAZARDOUS VOLTAGES ARE PRESENT WITH THE INDICATOR HOUSING OPENED AND AC POWER IS APPLIED, USE CARE WHEN MAKING ALL MEASUREMENTS.

  • Page 28: Battery Testing

    THE CKW INDICATOR FOR PROPER CHARGING. 3.4.1 General Information The optional battery used in the CKW-55 Indicator and the CKW-55 Series Scale is Nickel Metal Hydride, (NiMH), 7.2 Volts rated at 3800mA and is rechargeable. The battery assembly is internally fused and includes a battery monitor chip.
  • Page 29 CHAPTER 3 INDICATOR TESTING 3.4.2 Troubleshooting the Battery (Cont.) 3. Note the charging status of the battery. If the red bar graph is lit, either the battery and or the charging PCB has failed. Note: To force a charge cycle, see section 3.5.1. 4.

  • Page 30: Recharge Board Testing

    CHAPTER 3 INDICATOR TESTING 3.5 RECHARGE BOARD TESTING The Recharge Board is supplied with the optional rechargeable battery. This test is made when the battery fails to charge properly. The Recharge board is equipped with a soldered in place Fuse F1 located near connector J1 on the board.

  • Page 31: Recharge Board Testing

    CHAPTER 3 INDICATOR TESTING 3.5.1 Recharge Board Information (Cont.) The battery voltage and temperature are monitored while charging. An over voltage or temperature condition during the charge cycle will halt the charge sequence. A normal battery charge is about 5 hours. This time may increase as the batteries age. The faster charge times are achieved when the scale is off and connected to the AC power.

  • Page 32: Voltage Measurements

    CHAPTER 3 INDICATOR TESTING 3.5.2 Recharge Board Testing (Cont.) 9. Using an Ohmmeter, check the fuse F1, (refer to Figure 3-6) on the Recharge board to see if it is open. If the fuse is open, remove the Recharge board and replace the fuse. Re-install the recharge board in the housing.

  • Page 33: Relay Board Testing

    CHAPTER 3 INDICATOR TESTING 3.6 RELAY BOARD TESTING The Relay Board is supplied as an optional kit for the CKW-55 Indicator. 3.6.1 Relay Kit Information Two optional Relay Kits are available for CKW Series Indicators. The AC Relay Kit is used for controlling up to three external AC circuits.

  • Page 34: Relay Board With Terminal Cover

    CHAPTER 3 INDICATOR TESTING 3.6.2 Relay Testing (Cont.) Figure 3-7 Relay Board with Terminal Cover. Figure 3-8. Relay Board without Terminal Cover. 3-14...
  • Page 35 CHAPTER 3 INDICATOR TESTING 3.6.2 Relay Testing (Cont.) NOTE: When testing the Relay board containing dc type relays, an Ohmmeter providing a minimum of 5 Volts DC can be used to verify operation. When testing ac type Relays, a small circuit consisting of a low voltage (24 V AC) isolation transformer and small lamp (24 Volts) are required.

  • Page 36: Rs322, Rs422/485 Communication Testing

    Main PC board. In addition, an optional RS422/485 Communication Board is supplied as a kit for the CKW-55 Indicator and can provide a serial interface to Industry EIA-422/485 standards. A failure of RS232 communications would require replacement of the Main PC board. When the optional kit is installed, either the RS232 or RS422/485 can be used, not both.

  • Page 37: Serial Interface Commands Table

    (The unit can not be selected if it is not enabled). Print model name, software revision, and LFT status - if on, (eg. “CKW-55 Sr 1.0 LFT “On”, or “CKW-55 Sr 1.1” Set a pre-tare value of x, in present weighing units.* (Positive values only) All commands sent to the Indicator must be terminated with a carriage return (CR) or carriage return-line feed (CRLF).

  • Page 38: Rs422/485 Testing

    CHAPTER 3 INDICATOR TESTING 3.7.3 RS422/485 Testing The RS422/485 Communication board can be wired to operate in a 4-wire duplex or 2-wire half duplex mode. When RS422/485 is installed, note the jumper arrangement shown in Figure 3-10 and 3-11 RS422/485 Typical 4-Wire and Typical 2-Wire Connections. Note: W1 must be shorted to allow 2 wire communications.

  • Page 39: Rs422/485 Location In Housing

    CHAPTER 3 INDICATOR TESTING 3.7.3 RS422/485 Testing (Cont.) 1. Disconnect power from the Indicator. (Remove the line cord plug from the power source.) 2. Open the Front Housing, refer to procedure 4.1. NOTE: Make sure the computer is equipped with RS422/485 communications or a suitable converter.

  • Page 40: External Input Testing

    3.8 EXTERNAL INPUT TESTING The CKW-55 Indicator I/O menu contains an INPUT menu item that is used to define a function to be controlled by an optional external input device such as a foot switch. The switch must to be a momentary contact type and the contacts must be normally open.

  • Page 41: Operational Testing

    CHAPTER 3 INDICATOR TESTING 3.9 OPERATIONAL TESTING This section of the manual contains operational testing procedures of the CKW-55 Indicator. After servicing the CKW-55 Indicator and replacing defective boards, an operational test and various performance tests should be made to ensure the Indicator meets all specifications. Before checking the Indicator, refer to sections 3.11 or 3.12 and calibrate.

  • Page 42: Turning Off The Indicator

    CHAPTER 3 INDICATOR TESTING 3.9.1 Indicator Display Segment Test – Power On Sequence (Cont.) After power source information, Options list is displayed for 0.5 sec. each (if installed). If none installed, proceed directly to active weighing mode: bAt OP BAT OP (when battery option installed), RLY OP (when relay output option is installed), rLy OP 485 OP...
  • Page 43 CHAPTER 3 INDICATOR TESTING 3.9.4 Checking Menu Libary Settings In some cases, improper menu settings give the appearance of a failure. If the Main PC board is functional, this check can be made easily. It is required that either a printer or computer be connected to the Indicator RS232 terminals.

  • Page 44: Checking Menu Library Settings

    CHAPTER 3 INDICATOR TESTING 3.9.4 Checking Menu Library Settings (Cont.) Typical Computer or Printer Output of Menu Settings Auto-Zero Tracking = 0.5d Baud Rate = 2400 OHAUS CKW-55 Display Brightness = High Parity = None Software Version = Sr1.29 Bar Brightness = Mid...

  • Page 45: Specifications

    CHAPTER 3 INDICATOR TESTING 3.10 SPECIFICATIONS Table 3-4 lists the specifications for the Indicator. Scale Model specifications are also included. TABLE 3-4. SPECIFICATIONS INDICATOR CKW-55 Maximum Displayed Resolution 1:20,000 Approval Resolution 1:10,000 Weighing Units kg, lb, g, oz, lb:oz, %...

  • Page 46: Calibration Using An External Base

    CHAPTER 3 INDICATOR TESTING 3.11 CALIBRATION USING AN EXTERNAL BASE After the indicator has been repaired, calibration should be performed using a known good base. It is not necessary to pass the cable through the liquid-tight connectors for this procedure. 1.

  • Page 47: Calibration3-28

    Figure 3-13. Open and Shorted Jumpers. 3.12 CALIBRATION When the CKW-55 Indicator is initially set up with a base, it must be calibrated before use to ensure accurate weighing results. Complete CKW Scale models are shipped pre-calibrated from the factory. However, many conditions may require that the scale be recalibrated.

  • Page 48: Linearity Calibration

    CHAPTER 3 INDICATOR TESTING 3.12.1 Span Calibration (Cont.) 3. Press the Yes button to select and perform Span Calibration..4. The display flashes 0, indicating that nothing should be placed on the platform at this time. 5.

  • Page 49: Calibration Test

    CHAPTER 3 INDICATOR TESTING 3.12.2 Linearity Calibration (Cont.) 5. If a different mid-point Linearity Calibration value is desired, enter the new value via the numeric keypad. NOTE: The mid-range mass should be used for precise calibration. If the correct mass is not available, 25% to 75% full scale Capacity mass can be used.

  • Page 50: Geographical Adjustment Factor

    CHAPTER 3 INDICATOR TESTING 3.13 Geographical Adjustment Factor This menu item is used to allows entry of values from 0 to 31 and is used to compensate for variations in gravity at different geographical locations around the world.( Complete Geographical Adjustment ( Complete Geographical Adjustment ( Complete Geographical Adjustment ( Complete Geographical Adjustment...

  • Page 51: Geographical Adjustment Values

    CHAPTER 3 INDICATOR TESTING 3.13 Geographical Adjustment Factor TABLE 3-5. GEOGRAPHICAL ADJUSTMENT VALUES. Elevation above sea level in meters Geographical latitude 1300 1625 1950 2275 2600 2925 3250 away from the equator, 1300 1625 1950 2275 2600 2925 3250 3575 (North or South) in Elevation above sea level in feet degrees and minutes.

  • Page 52: Main Printed Circuit Board Connections

    CHAPTER 3 INDICATOR TESTING 3.14 CALIBRATION VERIFICATION USING A LOAD CELL SIMULATOR To perform these tests, the use of a Load Cell Simulator is required. The basic function of a Simulator is to simulate the output of a full bridge Load Cell allowing the Indicator to be separated from the Load Cell for the purposes of troubleshooting and calibration.

  • Page 53: Calibration Verification Using Load Cell Simulator

    CHAPTER 3 INDICATOR TESTING 3.14 CALIBRATION VERIFICATION USING A LOAD CELL SIMULATOR (Cont.) 5. When connecting a 3 mv/v Simulator: Jumper W1 must be removed or left in place with one pin uncovered. See Figure 3-15. 6. When connecting 4-wires with no sense wires: Jumpers W2 and W3 must be in place shorting the two pins.

  • Page 54: Load Cell Output Readings For Ckw Bases

    CHAPTER 3 INDICATOR TESTING 3.14.1 Calibration Test Using a Simulator (Cont.) TABLE 3-6. LOAD CELL OUTPUT READINGS FOR CKW BASES. NOMINAL OUTPUT IN MILLIVOLTS AT 5 VOLTS EXCITATION CAPACITY ZERO 100% 3 kg 4.3 +2.0 Zero + 2.3 Zero + 4.7 6 kg 1.6 +2.0 Zero + 2.8...

  • Page 55: Chapter 4 Repair Procedures

    CHAPTER 4 REPAIR PROCEDURES 4. REPAIR PROCEDURES This section describes how to replace individual assemblies of the CKW-55 Indicator. When doing this, please refer to the exploded view drawings and parts lists in Section 5. Important: After repairs are complete, an operational test of the Indicator must always be carried out, (see Section 3.9).

  • Page 56: Replacing The Main Pc Board

    CHAPTER 4 REPAIR PROCEDURES 4.2 REPLACING THE MEMBRANE SWITCH (Cont.) 9. Connect the cable from the Membrane Switch to connector J1 on the Main PC board. 10.Position the Front Housing into place over the Rear Housing and reassemble by replacing the four screws on the sides of the housing.

  • Page 57: Replacing The Optional Recharge Board

    CHAPTER 4 REPAIR PROCEDURES REPLACING THE POWER SUPPLY (Cont.) 6. Replace the Power board and install the four screws previously removed. Make sure the grounding clip is in place under the screw head shown in figure 3-11. 7. Reconnect connectors CN1 and CN2 to the Power board. 8.

  • Page 58: Relay Replacement

    CHAPTER 4 REPAIR PROCEDURES 4.6.1 Relay Board Replacement Procedure (Cont.) 4. Remove the four screws holding the Relay board in place and remove the Relay board. 5. Replace the Relay board and install the four screws previously removed. 6. Reconnect wiring to the Relay board and replace terminal cover. 7.

  • Page 59: Replacing The Optional Rechargeable Battery

    CHAPTER 4 REPAIR PROCEDURES REPLACING THE OPTIONAL RECHARGEABLE BATTERY The rechargeable battery is supplied as part of an optional kit complete with a recharge board. If the battery requires replacement, it can be replaced separately, the recharge board does not have to be replaced with it unless defective.

  • Page 60: Replacing The Real-Time Clock (Rtc) Battery

    CHAPTER 4 REPAIR PROCEDURES 4.9 REPLACING THE REAL-TIME CLOCK (RTC) BATTERY The Real Time Clock battery is mounted on the Main PC board. When the time and date cannot be set or loses the setting after AC power is removed, the battery must be replaced. NOTE: Read this procedure through first before proceeding.

  • Page 61: Chapter 5 Parts Lists

    CHAPTER 5 PARTS LISTS 5. PARTS LISTS This section of the manual contains exploded views, and parts lists for the CKW-55 Indicator. The exploded view drawings identify the replaceable parts. NOTE: In all cases where a part is replaced, the Indicator must be thoroughly checked after the replacement is made.

  • Page 62: Ckw-55 Indicator Exploded View

    CHAPTER 5 PARTS LISTS 5.1 CKW-55 INDICATOR EXPLODED VIEW Figure 5-1. Exploded View of CKW-55 Indicator.

  • Page 63: Ckw-55 Indicator Parts List

    CHAPTER 5 PARTS LISTS 5.2 CKW-55 INDICATOR PARTS LIST TABLE 5-1. CKW-55 INDICATOR PARTS LIST ITEM NO. PART NO. DESCRIPTION 71154791 Switch, Membrane CKW 71209058 Hardware, Kit, Housing Screws 71152473 PCB, Main, CKW 71173386 Fuse, Radial, 2.5A/250. TR5. UL/VDE, CKW...

  • Page 64: Ckw-55 Column Exploded View

    CHAPTER 5 PARTS LISTS 5.3 CKW-55 COLUMN EXPLODED VIEW Figure 5-2. Exploded View of CKW Column. TABLE 5-2. CKW-55 COLUMN PARTS LIST. ITEM NO. PART NO. DESCRIPTION 71167972 Column Mount Accessory, SS, CKW Tube, 230mm 80251059 Column Mount Accessory, SS, CKW Tube, 6800 mm...

  • Page 65: Appendix A Service Mode

    APPENDIX A SERVICE MODE A.1 SERVICE MODE This section of the manual contains service mode commands. A.1.1 Service Mode Commands: The Service Commands are only enabled after the scale receives a <esc>SV command through the RS- 232 interface. This command sets the scale into the Monitor mode. The Monitor mode is exited when the scale is turned off with the ON/ZERO Off button or a power off/on cycle, or a command is received which resets the scale.

  • Page 66: A-2 Ascii Number To Character Conversion

    APPENDIX A SERVICE MODE Table A-2 lists the ASCII to Character conversions used to enter library data. TABLE A-2 ASCII NUMBER TO CHARACTER CONVERSION ASCII Character ASCII Character ASCII Character space ‘ “ & < >...
  • Page 68 Ohaus Corporation 19A Chapin Road, P.O. Box 2033 Pine Brook, NJ 07058, USA Tel: (973) 377-9000, Fax: (973) 944-7177 www.ohaus.com With offices worldwide. www.ohaus.com *80251063* P/N 80251063 © Ohaus Corporation 2006, all rights reserved. Printed in USA...

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