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CHAPTER 3 REPAIR PROCEDURES

3.2.4 Load Cell Assembly

26. Set the top Load Cell Cover in place. Press evenly against the bottom cover.

NOTE:

Make sure the cover does not touch any screws.

Figure 3-87. Top Load Cell Cover rests flush against bottom cover.

27. Tighten the screws, as shown in Figure 3-88.

Figure 3-88. Tightening screws on top Load Cell Cover.

Discovery Balance Service Manual

3-43

Ohaus Corporation www.ohaus.com

Summary of Contents for DISCOVERY BALANCE

Page 1: ...SERVICE MANUAL DISCOVERY BALANCE Ohaus Corporation 19A Chapin Road P O Box 2033 Pine Brook NJ 07058 2033 973 377 9000...

Page 2: ......

Page 3: ...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 Material in this manual is subject...

Page 4: ......

Page 5: ...assembly 3 15 3 2 1 Load Cell Removal 3 15 3 2 2 Load Cell Disassembly 3 20 3 2 3 Load Cell Cleaning 3 30 3 2 4 Load Cell Assembly 3 31 3 2 5 Installing Load Cell 3 45 CHAPTER 4 TESTING 4 1 Testing 4...

Page 6: ...es Not Respond to Front Panel Controls 2 3 2 3 No Display or Partial Display 2 3 2 4 Balance Cannot Calibrate Using External Weights 2 4 2 5 Balance Cannot Calibrate Internally 2 5 2 6 Error Codes 2 6...

Page 7: ...the Load Cell 3 17 3 25 Lifting off Load Cell Cover 3 17 3 26 Load Cell with cover removed 3 18 3 27 Removing Cantilever Arm from Load Cell 3 18 3 28 Bottom Housing of Load Cell 3 18 3 29 Load Cell c...

Page 8: ...over 3 36 3 73 Up Down Stop Plate inserted over Ratio Beam tab and PCB screw receptacle on Magnet Cover 3 36 3 74 Load Cell PCB is secured with 2 screws with Step Bushing on the back 3 36 3 75 Fine wi...

Page 9: ...k edge light right edge heavy and right edge light conditions 4 4 4 5 Com 1 Connector as it appears on balance s back cover 4 7 4 6 AC Adapter Cord 4 9 5 1 Discovery Balance Housing 5 1 5 2 Discovery...

Page 10: ...TABLE OF CONTENTS Ohaus Corporation www ohaus com vi Discovery Balance Service Manual...

Page 11: ...ns Used to update software restore EEPROM data install a new Main Printed Circuit Board and install a new Load Cell Before servicing the balance you should be familiar with the Instruction Manual Part...

Page 12: ...unning Microsoft Windows NT 4 0 or later or Microsoft Windows 98 or later 3 Discovery Instruction Manual Part No 80104130 4 MFR Service Toolset Part No 80030340 Figure 1 1 Service Toolset Part No 8003...

Page 13: ...1 1 Use the minimum number of masses to total the calibration point value Table 1 1 MASSES USED TO TEST DISCOVERY BALANCES SPAN CALIBRATION POINTS WEIGHT CLASS MODEL CAPACITY g DEFAULT ALTERNATE ASTM...

Page 14: ...els 3 momme Custom unit Application Modes Weighing Parts Counting Percent Weighing Checkweighing Animal Dynamic Weighing G N T Totalization High Point Density Statistics Pipette Tare Range To Capacity...

Page 15: ...e next remedy Before attempting to repair the balance read all chapters of this manual to be familiar with the balance components and operation 2 2 1 Diagnosis 1 Isolate and identify the symptom 2 Ref...

Page 16: ...ating fingers on top housing defective Main PC Board is defective Check the main power source outlet for proper voltage See Table 2 2 If the balance fails to turn on and On Zero Off switch is OK the M...

Page 17: ...t present on a particular switch replace the affected switch or actuator If the balance fails to turn on and On Zero Off switch is OK the Display PC Board may be defective and should be replaced Displ...

Page 18: ...are used Set the Setup Menu Legal For Trade setting to Off See Instruction Manual Sections 3 7 12 3 8 Level balance Perform Automatic Internal Calibration Appendix A 1 If the balance fails to calibra...

Page 19: ...veling feet on rear of chassis together with leveling bubble just inside the left Door Side Draft Shield Disassemble the InCal Weight Hardware and test it InCal Weight Hardware Disassembly Testing 3 1...

Page 20: ...ta using Software Service Tool See Appendix C 1 Replace Main PCB Error 9 5 Production calibration not present Perform Service Calibration See Appendix B Error 9 8 User calibration data not present Req...

Page 21: ...icate Handle with care 3 1 1 Housing Disassembly Opening the Balance To disassemble the balance refer to Figure 3 2 Components shown below must be removed before gaining access to the inside of the ba...

Page 22: ...ng the Balance 1 Remove the two screws shown and then the third one on the bottom Figure 3 2 Removing back cover 2 Remove the back cover Back Screw Figure 3 3 Balance with Back Cover removed Ohaus Cor...

Page 23: ...ockwise four to five turns Figure 3 4 Scale bottom showing Draft Shield Assembly 6 Set the balance back on its feet 7 The Draft Shield Assembly should slide back approximately one quarter inch If not...

Page 24: ...removed and also cover of main Printed Circuit Board removed NOTE When replacing cover place keyway holes over cone shaped brass screw heads Keyway hole on Balance cover Figure 3 6 Keyway hole on cov...

Page 25: ...e replaced Table 3 1 Display Assembly Parts List Drawing Item Description 1 In Use Cover 2 Function Label 3 Display Housing Upper 4 Printed Circuit Board PCB Display 5 Display Cable 6 Display Housing...

Page 26: ...move the 6 screws securing the Display PCB and lift out the PCB CAUTION WHEN HANDLING THE PRINTED CIRCUIT BOARD HANDLE BY EDGES ONLY DO NOT TOUCH FOIL SIDE OF BOARD STATIC DISCHARGE MAY DAMAGE SOME CO...

Page 27: ...To replace the main Printed Circuit Board proceed as follows 1 Open the Housing by referring to Section 3 1 1 Main PCB Cover Screws RS232 Screws Figure 3 9 Display Balance Load Cell Cover 2 Remove 2 s...

Page 28: ...OME COMPONENTS ALWAYS USE AN ANTI STATIC KIT 4 Disconnect the cables from the PCB 5 Remove the 3 screws securing the PCB 6 Remove the PCB 7 Before installing the new PCB remove its EEProm chip and rep...

Page 29: ...ble balance Follow Sections 3 1 2 and 3 1 3 in reverse order NOTE Be careful when replacing the PCB Cover to avoid bending the teeth that secure the Cover to the Mounting Plate The Cover should rest o...

Page 30: ...f the mechanism might have come out of position or dust or debris might have entered the mechanism Depending on the balance capacity Error 8 3 Weight reading above underload limit may be displayed whe...

Page 31: ...te A clean glove should be worn when handling Weights Figure 3 15 Weights and Weight Holders can be removed but should only be handled while wearing a clean glove 5 Remove both Weights and Weight Hold...

Page 32: ...hat secure the Weight Holders Then carefully place the Weights in their Holders 9 As each Weight Arm moves inward when its Partial Load button is clicked check that the Weight above it is lowered into...

Page 33: ...tion Motor Assembly installed to the right of the Load Cell Screws securing Calibration Motor Assembly to Balance chassis Figure 3 18 Calibration Motor Assembly closeup Note screws on right securing i...

Page 34: ...new Calibration Motor Assembly will make installation easier Figure 3 19 Calibration Motor Assembly Figure 3 20 Calibration Motor close up showing cam in rest position 3 Install new the Calibration Mo...

Page 35: ...from its protective housing Prior to opening the Load Cell be sure to have the Service Toolset Part No 80030340 which includes a fixture that must be installed to protect the Flexures during both dis...

Page 36: ...Weights and weight holders can be removed but should only be handled while wearing a clean glove This will leave only the Platform Holder on the chassis 5 Remove both weights and weight holders and se...

Page 37: ...its Mounting Plate as shown in Figure 3 24 Figure 3 24 Lifting off the PCB and its Mounting Plate from the Load Cell 10 Lift off the Load Cell Cover It has no screws Figure 3 25 Lifting off Load Cell...

Page 38: ...upward with the thumb then sliding away from the Load Cell Cantilever Arm Figure 3 27 Removing Cantilever Arm from Load Cell 12 Tilt the balance onto its back and remove the 3 screws that secure the...

Page 39: ...the front of the balance See Figure 3 29 Load Cell keyway inside chassis Figure 3 29 Load Cell chassis Note position of keyway facing towards front of balance 14 Disconnect the cable from the Load Cel...

Page 40: ...om covers Be careful of the Flexure Arm assemblies Figure 3 31 Removing screws from Figure 3 32 Load Cell with top cover removed Load Cell top cover Figure 3 33 Removing screws from Load Cell bottom c...

Page 41: ...bly to frame Screw connecting bottom Flexure Arm assembly to frame Figure 3 35 Screws on bottom Flexure Arm assembly Screw connecting top Flexure Arm assembly to frame Screw connecting top Flexure Arm...

Page 42: ...ell is delicate Handle with care The following steps are performed to protect the Flexures during the disassembly process Figure 3 38 Brass Fixture inserted part way under the Load Cell s Hanger Brass...

Page 43: ...ews and Hanger on top of Load Cell It is now safe to remove the Load Flexure Load Flexure Screws Figure 3 41 Screws securing Load Flexure to Hanger on top of Load Cell 8 Carefully remove the two screw...

Page 44: ...crews connecting Flexure Arm to Load Cell frame Screws Washers Flexures Figure 3 44 Removing the top Flexure Arm 10 Before removing the bottom Flexure Arm secure the Ratio Beam by installing the threa...

Page 45: ...her side of the set screw atop the Load Cell s PCB 13 Remove the solder with a solder sucker to clear holes in PCB so the wires can pass through when you need to solder them back in place 14 Use tweez...

Page 46: ...n when the Up Down Stop Plate is removed Proceed as follows 15 On the back of the Load Cell lift the Ratio Beam and insert the brass rod under it Figure 3 46 Lifting Ratio Beam to insert Brass Rod Fig...

Page 47: ...g the PCB unsolder the two Temperature Sensors as shown in Figure 3 51 Then remove the Temperature Sensors and set them aside Remove the Temperature Sensors from the new PCB Insert and solder the Temp...

Page 48: ...moving Temperature Conductor 19 Remove the Temperature Conductor as shown in Figure 3 53 20 Remove the two screws that secure the Magnet Cover and carefully remove the Magnet Cover by lifting it strai...

Page 49: ...ass Fixture Note uncovered Magnet in background Figure 3 57 Removing Thumb screws that hold Hanger in place Brass Fixture will be released 22 Release Ratio Beam yoke by removing screws on each side Sc...

Page 50: ...the Temperature Sensor Tube Figure 3 61 Magnet gap and Temperature Sensor Tube should be carefully examined for dust and debris Figure 3 62 Coil Assembly should be carefully examined and cleaned NOTE...

Page 51: ...eam yoke with Load Cell frame Screw on side of yoke Screw on side of yoke Ratio Beam Flexure Ratio Beam Flexure Figure 3 63 Yoke of Ratio Beam must align with frame of Load Cell 2 Insert Brass Rod on...

Page 52: ...s must be checked to see if they are bent Place each Flexure on a clean flat surface and check that both sides rest evenly on the surface If they don t replace them 3 2 5 1 Ratio Beam Flexure Replacem...

Page 53: ...ass Rod in rear 5 11 Screw Threaded Rod back in 5 12 Remove Brass Brackets and ensure that Ratio Beam is visually centered If not loosen Threaded Rod and adjust Ratio Beam to center it Then tighten Th...

Page 54: ...the Ratio Beam moves correctly reinstall the Brass Rod and Threaded Rod 9 Install the Hanger with the Brass Fixture and the Thumb Screws from the Service Toolset The Brass Fixture is inserted between...

Page 55: ...nserting the Temperature Conductor in the middle of the Magnet Cover Figure 3 71 The Temperature Conductor groove should line up with the two Screws 13 Insert the Temperature Conductor in the middle o...

Page 56: ...p Plate which rests on Magnet Cover 15 Install the Up Down Stop Plate as shown in Figure 3 72 16 Place Load Cell PCB over screw receptacles on Magnet cover and secure with 2 screws shown in Figure 3 7...

Page 57: ...the solder holes 17 2 Use tweezers to thread the fine wires through the solder holes 17 3 Carefully replicate the original smooth arc of the wires as shown in Figure 3 71 to ensure proper functioning...

Page 58: ...should support the weight of the Load Cell and not the Ratio Beam Rod Screw See Figure 3 72 Load Cell Note Make sure Threaded Rod is used to protect Ratio Beam Rod from the Load Cell s weight Threade...

Page 59: ...ng bottom Flexure Arm to frame Figure 3 77 Installing the bottom Flexure Arm 19 After the bottom Flexure Arm Assembly is installed remove the Threaded Rod 20 Install the top Flexure Arm with Flexure s...

Page 60: ...ed screw hole goes on the bottom Figure 3 80 Load Flexure aluminum washers steel washers and screws Figure 3 81 Load Flexure on top of Hanger with elongated screw hole at bottom 22 Gently tighten the...

Page 61: ...82 Hanger with Thumb screws removed Thumb screw holes 24 Push the Brass Fixture from the grooved side then pull it out from the square side Figure 3 83 Pushing Brass Fixture from grooved side Figure 3...

Page 62: ...t to the stops then insert and tighten screws on both sides Stops on sides of bottom Load Cell cover Screw holes Figure 3 85 Note stops on sides of bottom Load Cell Cover Figure 3 86 Tightening screws...

Page 63: ...ainst the bottom cover NOTE Make sure the cover does not touch any screws Figure 3 87 Top Load Cell Cover rests flush against bottom cover 27 Tighten the screws as shown in Figure 3 88 Figure 3 88 Tig...

Page 64: ...URES 3 2 4 Load Cell Assembly 28 Gently push on the Hanger to make sure it moves freely and smoothly Figure 3 89 Hanger should move smoothly when touched Ohaus Corporation www ohaus com 3 44 Discovery...

Page 65: ...er Arm sliding it under the Hanger so that its stop shelf rests on lower lip of Hanger and grooves hook into the feet of the Hanger Cantilever Arm Left side of Hole under Cantilever Arm Right side of...

Page 66: ...ible cable on Load Cell using the back of a pair of tweezers to press cable into place Also connect cable on Calibration Motor Assembly 6 Place the Load Cell Cover over the Load Cell Figure 3 93 Repla...

Page 67: ...he Load Cell Cover Cable from Load Cell to PCB lies flat in slot beneath PCB Mounting Plate Figure 3 95 Placing PCB Mounting Plate on Load Cell 9 Insert copper colored stand off screws through holes i...

Page 68: ...s and Weight Holders Note A clean glove should be worn when handling Weights Figure 3 97 Installing Weights and Weight Holders 11 3 Place the InCal Weight Cover over the Weights aligning the screw hol...

Page 69: ...sed groove 14 Before tightening the screws in the Display Cable Shield Plate check that the Pan Socket is centered in the hole Then tighten the screws See Figure 3 99 Display Cable Shield Plate Screws...

Page 70: ...Breeze Ring and Breeze Ring Base following the steps in Section 3 1 1 in reverse order 17 If a new Load Cell has been installed connect the balance to a personal computer with the Discovery Software...

Page 71: ...voltage use an appropriate adapter to match the supply voltage 4 1 2 Models Segment Display Test 1 Turn the balance on by pressing ON ZERO Off all segments are enabled and displayed briefly then foll...

Page 72: ...perform adjustment as follows 1 Pop out the hole plugs and insert both Allen Keys from the Service Toolset as shown in Figure 4 2 Allen Key inserted in pop out hole in back cover Allen Key inserted i...

Page 73: ...avy It is a positive value that is greater than the tolerance specification The opposite side of the Pan which is lighter has a negative value that is less then the tolerance specification When moving...

Page 74: ...ss Reading should return to 0g 1 count 4 Repeat the test for ten readings If the standard deviation of the readings is within the specifications in Table 1 2 Discovery Balance Model Specifications pag...

Page 75: ...40 80 120 160 DV215CD 1 Place the test mass on the balance record the weight and remove 2 Place Load 1 on the balance and press TARE 3 Place the test mass on the balance record the weight and remove...

Page 76: ...the submenu to change the Baud settings Baud rates can be set from the range of 600 to 19 200 The default setting is 9600 Parity Use the submenu to change the Parity settings Parity can be set to 7 O...

Page 77: ...4 3 2 1 9 8 7 6 Figure 4 5 Com 1 Connector as it appears on balance s back cover TABLE 4 2 COM1 INTERFACE PIN CONNECTIONS 1 Not used 2 TxD 3 RxD 4 DSR 5 Ground 6 DTR 7 CTS 8 RTS 9 Not used Discovery B...

Page 78: ...ble CP Continuous Print OP ends Continuous Print SP Print displayed stable weight SLP Auto Print stable non zero displayed weight SLZP Auto Print stable non zero weight and stable zero reading xP Inte...

Page 79: ...y 4 6 Testing the AC Adapter The AC Adapters are available with different input voltages Before testing the Adapter make sure the Adapter rating agrees with the power source being used All Adapters ar...

Page 80: ...Pan Shield 6 Door Side Draft Shield 7 Back Wall Draft Shield 8 Back and Front Strip Set 9 Glass Bottom Draft Shield 10 Platform Grommet 11 Door Track Set Draft Shield 12 Glass Front Draft Shield 13 Do...

Page 81: ...ERY DISPLAY ASSEMBLY Drawing Item Description 1 In Use Cover 2 Function Label 3 Display Housing Top 4 Display Printed Circuit Board PCB 5 Display Cable 6 Display Housing Bottom Figure 5 2 Discovery Ba...

Page 82: ...3 Main Printed Circuit Board PCB w EEROM Battery 4 Blank EEROM 5 Complete Load Cell 6 Leveling Foot 7 Calibration Motor Assembly 8 Calibration Weight Arm 9 Calibration Weight Holder 10 InCal Weights C...

Page 83: ...rew 5 Lower Flexure Arm Assembly 6 Lower Front Flexure 2 washers screw 7 Cantilever Arm 8 Load Flexure 9 Upper Flexure Arm Assembly 10 Ratio Beam Flexure 2 washers screw 11 Magnet Cover 12 Temperature...

Page 84: ...Adj Calibration Adjustment allows adjustment of the internal calibration to match an external calibration weight Note Calibration will be locked out if the balance is in Legal For Trade mode To regain...

Page 85: ...mode AutoCal will automatically calibrate the balance each time there is a change in temperature significant enough to affect accuracy or after every 11 hours In certain circumstances a user may need...

Page 86: ...ted weight in the Pan Calibration will begin 100 ADD WEIGHT The SPAN BUSY message flashes while the balance reads the maximum weight setting SPAN BUSY When the maximum weight reading is taken the Clea...

Page 87: ...d Press No CAL SPAN is displayed Press No CAL CAL TEST is displayed Press Yes and follow the screen instructions CAL TST_CLEAR PAN appears for a split second Be sure the Pan is clear 100_ADD WEIGHT ap...

Page 88: ...dures With the balance on press and hold Cal Menu until Menu Calibrate is displayed with CALIBRATE blinking then release the button Press Yes to enter calibration CAL AUTOCAL is displayed Press No CAL...

Page 89: ...n In general a blinking item in the primary or secondary display indicates a choice Pressing Yes selects the displayed sub menu Pressing No causes the next sub menu to appear B 2 Entering the Service...

Page 90: ...ew the Ramp value press Yes A number will appear on the lower portion of the display and should be constant Place masses on the balance from minimum to maximum capacity The reading will increase but s...

Page 91: ...ars In a few seconds the Add Weight message appears with the number corresponding to the required weight Span BUSY Add the amount of weight indicated 100 ADD WEIGHT A Busy message will appear together...

Page 92: ...Side Draft Shield After pressing No to Ramp and Span press Yes to start the internal calibration The INCAL Busy message appears INCal BUSY If the calibration is successful the INCAL Done message appe...

Page 93: ...oftware on a Personal Computer running Microsoft Windows NT 4 0 or later or Microsoft Windows 98 or later Insert the CD and run Setup exe After installation run the program Service Tool The program ha...

Page 94: ...the data file from Ohaus continue with the following steps 4 Connect the balance to the PC and start the Discovery Software Service Tool 5 Click the tab labeled Restore EEPROM Figure C 2 The Software...

Page 95: ...alance 4 Power the balance from an AC adapter 5 Connect the balance to your computer 6 Start the Discovery Service Tool Software 7 Click on the tab labeled Replace Loadcell Figure C 3 The Software Ser...

Page 96: ...4 The Software Service Tool s Replace PCB tab 4 Enter the S N value from the label on the back of the balance 5 Enter the IDNR number xxx xx xx xxxx from the label on the back of the balance 6 Click t...

Page 97: ...ab 4 Enter the path to the file to download or click the Change button to locate the file 5 Click on the Start Download button 6 When prompted disconnect the power from the back of the balance then re...

Page 98: ...esting Note This procedure is used to test that the Incal Weights move smoothly When each of the weights are in the lowered position the display reading should be STABLE 1 Click on one of the InCal We...

Page 99: ...80104135 P N 80104135 SERVICE MANUAL DISCOVERY BALANCE...

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