Service Manual - Frank`s Hospital Workshop
Contents
1. see drawing 08 06 04 541 If all cables are okay there is a fault on the AD converter or the microprocessor is not working properly If the supplementary AD converter board on model 748 is replaced the scale must be calibrated according to calibration instructions 30 34 00 446 and adjustment instructions 30 34 00 487 Important note Apply Sylgard 170 A amp B to seal the supplementary board The scale must be recalibrated Blatt 4 30 34 00 437 Index G Service Manual seca 717 727 728 737 757 Open the scale 1 1 Turn the scale over so that the bottom plate is at the top diagram 1 1 2 Slacken the four recessed head screws A 1 3 Turn the scale back over again and remove the baby tray Diagram 2 1 4 Does not apply for model 727 728 Release the recessed head screws B on the screening plate This gives you access to the board 2 Troubleshooting and replacement work on electronic components 2 1 Depending on the type of fault refer to Description of faults 30 34 00 437 for troubleshooting 08 01 98 Ha Blatt 1 2 3 2 3 3 4 4 1 5 5 1 5 2 5 3 4 2 Replacement instructions Display electronics Pull off the socket connector C from the board and from the display electronics Unsolder the cables from the test button and or the KG LBS selector switch and from the start switch D Slacken all the slotted screws E on the display and bubble level holder and replace them a2. stabilized until the hold function is activated the next time Monitoring the supply voltage A monitoring circuit for the supply voltage is connected to pin 14 of the uC which detects if the operating voltage is too low If this pin is at O potential the uC interrupts the normal measuring cycle and writes bAtt into the display If the scale is operated on rechargeable batteries the electronics are switched off after a few seconds via pin 8 of the uC in order to prevent exhaustive discharge Switch on time The switch on time is determined by the software as standard Continuous operation can be achieved by soldering in jumper 618 Power supply unit detection If a power supply unit is connected to the scale transistor 109 is switched through via the battery charging circuit see below This sets pin 33 of the micro controller to OV and the switch on time is extended in accordance with the software setting Power supply The circuit has the following special features Reliable function over a large input voltage range from 6 15 V at a controlled output voltage of 5V or 10V Low power loss Reset circuit By connecting a power supply unit a positive pulse is issued via high pass filters 116 and 117 and via diode 118 The same happens when the start button is pressed via 113 114 and 115 Resistor 112 ensures that capacitor 113 can be discharged when the start button is open The alternative connection for th
3. display shielded load cell 7 an und aus diesen R verbleiben ERN amp Halke mum Index Datum 05 02 98 Eingef nrt mit Dafun Name SECA HAMBURG s EE Gepr ft Datum index Ma stab Werkstoff EL n mE Function diagram 25 01 02 503 Circuit description Model 717 727 728 737 748 757 Associated circuit diagrams 1 A D converter circuit diagram 08 01 21 321 2 Microprocessor circuit diagram 08 01 21 322 3 Display unit circuit diagram 08 01 21 323 4 Switched mode power supply circuit diagram 08 01 21 354 Measuring element A platform load cell is used as the force measuring element 4 wire resistance strain gauges are attached to its surface at suitable points which are connected in a bridge circuit When a load is applied the spring body is deformed in such a way that the two resistors forming a half bridge are extended and compressed This causes the resistance to be increased or reduced so that the bridge is detuned causing a change in the output signal U k U F U F In order to ensure a higher signal yield for the seca 717 the measuring element and the A D converter are supplied with 10V usually a 5V power supply is provided Analog to digital converter The A C converter directly processes the small output signal of the strain gauge sensor It functions according to the principle of signal dependent pulse width modula
4. 252 009 plug in power supply unit 230V 50Hz mod 717 757 32 68 32 10 261 009 plug in power supply unit 12V 150mA mod 717 Japan 32 17 10 00 Reinhold Blatt 2 3 30 34 00 550Index f SN yore SS N H f SS C E nee SSS AY 1 H H CH i ae Mim 2227 L LEE Wb y en H an o H A A VAZ 2 ZA LE i ben Vv 7 2 RAL U 4 ck DE pga J LL IS Ersatzteilliste Mod 717 717A 757 SECA sureParts st mod Auen 30 34 Sep
5. 50 00 91 330 009 Setscrew DIN 913 M5x16 01 27 08 04 05 320 009 Support for operating and display elements 20 28 01 17 01 203 009 Bubble level d 15 15 29 14 05 01 461 009 Bubble level cover 10 30 08 06 16 064 119 Button 10 37 08 06 18 038 009 Display board 35 38 08 06 16 011 119 Cable harness for display board 24 39 01 22 13 223 009 Intermediate plate 15 43 08 04 05 319 009 Screening plate sides 10 44 08 04 05 318 009 Screening plate cover 10 47 02 03 01 248 008 Bottom part of baby tray model 757 only 36 48 02 03 01 230 008 Top part of baby tray model 757 only 36 17 10 00 Reinhold Blatt 1 3 30 34 00 550Index f seca 717A 717 japan 757 Spare parts list Item Article no Designation Price stage 49 02 03 01 254 009 Baby tray model 717 only 42 51 01 22 13 310 009 Front plate model 717 717 Japan 28 01 22 13 294 009 Front plate model 757 only 28 59 68 22 12 721 009 Set of rechargeable batteries Ni MH 7 2 V 1100 mAh model 757 only 33 61 08 06 12 067 009 Platform load cell 48 62 01 18 01 260 009 Push button with print 5g 2g model 717 only 08 63 01 18 01 254 009 Push button with print NET model 757 only 08 64 01 18 01 255 009 Pushbutton with print ON 08 65 01 18 01 256 009 Pushbutton with print HOLD 08 66 08 04 02 208 009 Mounting plate load cell 15 67 01 03 01 031 009 Pressure plate with Presti nut 15 68 01 09 04 011 009 Transport locking device compl 18 69 68 32 10
6. A D conversion Calculation of the zero point Binary BCD segment conversion Display control using multiplex operation A D converter test Testing the CPU and the memories RAM and ROM Overload detection Monitoring the supply voltage digital Automatic zero point monitoring Taring function Hold function All functions are implemented via software in the programmed memory ROM of the uC Sequence of operations 25 01 02 467 Index E Circuit description Model 717 727 728 737 748 757 When the start button is pressed the following steps are executed Starting The uC is started with the reset logics see below and the program is executed Self test A test digit is written into all of the RAM cells in succession then read out and compared The main CPU commands are checked via computer operations to see that they function correctly The sum of the digits of those memory values which are important for the weighing result is continuously calculated and checked for correctness In the event of fault EEEEE is written to the display Zero point determination After starting SECA is displayed for approx 1 second During this period the zero point is determined The measured value Mg obtained is saved and subtracted from the relevant measured values For incubator scale 748 only After SECA UP flashes in the display The scale must be relieved by at least 0 5 kg in order that the zero point can be det
7. PN transistor If the scale is operated on a power supply unit a voltage of approx 0 65 V should be present at the base of transistor 109 If this is not the case check whether the correct components have been fitted for LED 106 and resistors 107 108 Fault description Blatt 2 30 34 00 437 Index G Seca 717 727 728 737 748 757 7 Fault description Signal transmitter on model 748 not working To check the microprocessor output IC 520 Start the scale A voltage of 5 V must be present at pin 34 Load the scale with 5 kg and restart it UP flashes Relieve the scale by at least 1 kg 0 V must be present at pin 34 for approx 1 second If this is not the case replace resistor network 519 or the microprocessor IC 520 Check transistor 324 A voltage of approx 0 2 V must be present at the collector of transistor 324 Load the scale with 5 kg and restart it UP flashes Relieve the scale by at least 1kg 5 V must be present at the collector of transistor 324 for approx 1 second If this is not the case replace transistor 324 Check transistor 325 A voltage of approx 12 V or 9 V if the scale is operated on rechargeable batteries must be present at the collector of transistor 325 Load the scale with 5 kg and restart it UP flashes Relieve the scale by at least 1 kg 0 2 V must be present at the collector of transistor 325 for approx 1 second If this is not the case replace t
8. Variants 7177021008 7177021098 7177021248 7577021004 7577021094 Description High resolution approved baby scale with integrated LED display Content Operation Operation Operation Function diagram Function diagram Electronics Block diagram electronics Description of faults Replacement Calibration spare parts Manual number Service Manual for seca 17 05 01 249 f 717A 717 Japan 757 17 10 07 314 17 10 07 345 17 10 07 354 25 01 02 446 25 01 02 503 25 01 02 467 08 09 01 267 30 34 00 437 30 34 00 483 30 34 00 609 30 34 00 550 Service Manual Number 17 05 01 249 f Valid as of Valid until 30 08 00 5 Adem Dui 0Jado ui juoddns punog pydsip 91002 Jopo Sp 34D 25 310043818 Sep beet A fe KC i g Ges D em Bas amp A ial eer EE LES Der To Ee 0 SSD H gi ax rr MEE AE un CSS ge mme d uay UojJnq X LSL LEL Yapoui LLL moon Benennung 25 01 02 446D Function diagram 717 737 757 LLL LLL LL LL LL LL LL V AV AV AV AV AV AVAV AVAVAVAVAS SSW load cell platform VA A AA AV AVV AV AV AV AV AV AV AA AV AV AV AV AV AV AV AV AV AVA N RNS NN NS NNN NNN ANAS SN SAN SN e e e e NS SS NS NS DS DS NN e electronics
9. atteries make the following check Measure the rechargeable battery voltage and recharge the battery if necessary When the scale is operated on a plug in power supply unit make the following check The voltage at Z diode 102 must correspond to the power supply unit voltage If the voltage collapses there is a short circuit e g in diode 102 or the power supply unit is defective Check the 5 V supply voltage The voltage at capacitor 518 must be in the range 4 7 V 5 8 V Measure the voltage at pin 6 of IC 131 If it is lower than 6V replace diode 110 scale operated on rechargeable batteries or diode 111 scale operated with power supply unit Measure the voltage at pin 8 of IC 131 If after pressing the start button the voltage is lower than 6V check pin 8 of IC 126 with an oscilloscope When the start button is pressed a 23 04 97 Jen Description of faults short positive pulse must be registered If there is no pulse check the start button and diodes 115 and 118 otherwise replace IC 126 Measure the voltage at pin 1 of IC 131 It should be approx 5V If this is not the case check diode 132 and replace if required otherwise replace IC131 Check the reset circuit Check pin 13 of IC 126 with an oscilloscope When the start button is pressed a short positive pulse must be registered If there is no pulse replace IC 126 Check pin 9 of IC 520 with an oscilloscope If no short positive pulse is mea
10. ce reference reference A D converter voltage voltage voltage batt temperature compensation linearisation strain gauge bridge Zero handling Alle Rechfe an und aus diesen Unterlagen verbleiben Vogel amp Halke www SC 03 11 88 Datum Name 23 06 d Aschke 18 07 97 Wint 05 08 97 Aschke seca HAMBURG sezeichnet ta Gepr ft Ma stab Werkstoff electronics Sc Se 08 09 01 267 Seca 717 727 728 737 748 757 Troubleshooting First and foremost make a visual inspection checking the soldering points and for corrosion and soiling Also check that all parts are fitted correctly 1 Fault description Rechargeable battery not correctly charged Connect the scale to the plug in power supply unit For the correct battery charging current see list 30 34 00 561 Check the battery charging current Remove the rechargeable battery and connect an ammeter to the rechargeable battery connections If the charging current is not in the specified range check the polarity of diode 106 and correct if necessary anode at input voltage LED lit when charging current flows If the polarity is correct calibrate the charging current using resistor 103 If no charging current flows check transistor 104 and replace if required 2 Fault description The scale cannot be started When the scale is operated only on rechargeable b
11. e start button at pin 3 08 02 98 Law Blatt 3 3 of IC 126 prevents a reset when the scale is switched on and allows a start button to be used which is connected with the platform surface The pulse from diode 115 or 118 is transferred to the set input of flip flop 126 B Low pass filter 141 142 prevents a reset being triggered by conducted interference Resistor 119 is used as a pull down resistor for the set input As soon as flip flop 126 B is set capacitor 124 is charged via resistor 125 The flip flop is reset shortly afterwards The pulse generated at the output of 126 B switches on the 5V power supply via flip flop 126 A and transfers a 5V pulse to the controller via resistor 127 and transistor 128 Low pass filter 619 620 ensures that no reset is triggered by conducted interference Voltage stabilization The reset sets flip flop 126 A whose output sets the shut down input of switching controller 131 to high The latter generates a controlled voltage of 5V by means of diode 132 coil 133 and capacitors 129 130 134 and 135 By means of the LC combination 136 137 this voltage is smoothed for use in the A D converter region Using resistors 139 and 140 the control threshold is set above which the switching controller sends a low batt signal to the controller Resistor 138 is used as a pull up resistor here If the voltage is to be switched off again the controller switches the stop signal from high to low Re
12. ermined Once the zero point has been determined a sound is emitted for approx 1 second which signals that the scale is ready for weighing Zero point follow up If the current measured value Mj changes only slightly in relation to the zero point value Mg within a given time C 0 5 d sec the current measured value is regarded as the zero point Mj Mo Weight calculation The weight is calculated from the current measured value Mi minus the zero point value divided by ng ng is the internal step count per step displayed Fe a Mo n Here 10 Display The current weight F is displayed on a 7 segment LED display The display is controlled via multiplex operation Consequently actuation faults affect all segments and are detected immediately 08 02 98 Law Blatt 2 3 The uC outputs the processed 7 segment information to the segment port Via Darlington driver 419 8 transistors and resistor network 317 8 resistors the cathodes of the LED s are set to 0 V The shared anodes are connected to 5V via the relevant digit transistor Overload detection The current measured value Mj is checked with respect to two limit values 8 Overranging If F Fmax 9d STOP is displayed d graduation on the display b Overshooting the limit If F Flim Ca Fmax 20 EEEEE is displayed C A D converter limit values If the bottom or upper limit of the A D converter is overshot EEEEE is dis
13. played Range switch over for model 717 By pressing the weighing range switch over button where normally the tare button is fitted the scale can be switched over between weighing range 1 and 2 Weighing range 1 15kg 5g Weighing range 2 6kg 2g Hold and tare function for model 727 The Hold Tare button has two functions Tare range up to 0 4 kg Hold range from 0 4 kg Taring function for models 737 and 757 The taring function is activated by pressing the tare button Hold function for models 717 737 748 and 757 The hold function is activated by pressing the hold button Taring If the taring function is activated this is detected by the uC tare indicator 27 on the display board is Switched on and the weight on the scale is tared off The zero point is subtracted from the measured value Mi and the result is saved as Mt The weight now results from M M M n e F 25 01 02 467 Index E Circuit description Model 717 727 728 737 748 757 Zero follow up and overload detection continue to operate as usual whereas the measuring range is overshot if 14 M n e If measured value Mi is smaller than the zero point by the value Mr the taring function is cancelled again The value Mr is added again to the zero point and tare indicator 27 is switched off Hold operation If the hold function is activated the weight is retained on display as soon as the value has
14. ransistor 325 If the signal transmitter still does not work replace the signal transmitter 8 Fault description Scale does not display the correct weight Check the slope and adjust if necessary see manual adjustment instructions seca 727 No 30 34 00 448 seca 737 757 No 30 34 00 484 seca 748 No 30 34 00 446 9 Fault description Scale displays EEEE after starting Check fuse 450 or soldering jumper 450 and replace if necessary Check the load cell connections on the main board Check the zeropoint and adjust if necessary see manual adjustment instructions seca 727 728 No 30 34 00 448 seca 717 737 757 No 30 34 00 484 23 04 97 Jen seca 748 Blatt 3 Description of faults No 30 34 00 446 30 34 00 437 Index G Seca 717 727 728 737 748 757 748 Check the cables between the main board the supplementary board Check the soldered connections Measure the signals 5V GND REF TEST on the supplementary board Measure the COM signal on the main board If a signal is not transmitted replace the cable Please refer to the oscillograms below when checking the signals The pulse widths of the REF and COM signals vary with the load UN REF 1 2 3 4 5 6 7 t ms UN COM 1 2 3 4 5 6 7 tims 23 04 97 Jen Description of faults Check the force sensor connection Check the soldered connections for seca 748
15. rox 5 V If this is not the case replace the transistor 5 Fault description Segment defective Check the actuation of the segments with an oscilloscope Check the output of IC 419 To do so use an oscilloscope connected to the relevant pin to measure the segment actuation signal Output of IC 419 UN Ausgang von IC 419 2 4 6 8 10 12 14 tms 23 04 97 Jen Description of faults If the output does not switch replace IC 419 Check the output of microprocessor IC 520 or the input of IC 419 To do so use an oscilloscope connected to the relevant pin to measure the segment actuation signal Input of IC 419 UN Eingang vonIC 419 2 4 6 8 10 12 14 tms If the output does not switch replace the microprocessor 6 Fault description Mains operation monitor not working correctly If the scale is not loaded a scale operated on a power supply unit should switch off after 10 minutes If operated on rechargeable batteries the following applies seca 717 727 728 737 75T 1 minute seca 748 2 minutes Check transistor 109 If the scale is operated on a power supply unit a voltage of approx 0 2V must be present at the collector If this is not the case replace transistor 109 If when the scale is operated on rechargeable batteries a voltage of approx 0 2 V is present at the collector the wrong transistor was fitted a PNP instead of an N
16. s a set Fault on load cell and electronics In this case the load cell the bottom plate and the platform support must all be replaced Assembling the scale Assemble the scale in reverse order following steps 1 1 to 4 1 Adjust and check the scale in accordance with the instructions for manual calibration or adjustment seca 727 728 30 34 00 484 30 34 00 336 seca 717 737 757 30 34 00 484 30 34 00 488 Calibrate the scale Only applies for model 717 737 757 30 34 00 483 Index Model 717 Adjustment Instruction Procedure to adjust the scale model 717 1 Place the scale on a smooth ground and align it by means of a level device Pay attention that the scale is adapted to the environment temperature prior to the adjustment 1 Connect the scale with the Supply unit to the power Supply 2 Remove the calibration marks at the rear side of the scale that the rotary potentiometers underneath can be adjusted by means of r a screw driver see sketch 3 Select test weight which is nearly max weight 15 kg and calculate the set display N A to be achieved for the test f weight P taking into P consideration the acceleration due to gravity of the location 4 Start the scale wait until 0 0 is displayed and weight it with test weight P Adjust the display coarsly with potentiometer INCLIN COARSE and finely with potentiometer INCLIN FINE Adjustthe potentiometers such that the display of
17. sistors 121 and 122 as well as transistor 123 perform a level conversion and inversion of the signal so that a positive edge is given to the clock input of flip flop 126 A resetting it and switching off the 5V voltage For the seca 717 the 10V in phase regulator 451 is used which supplies the A D converter and the force measuring element using buffer capacitors 452 453 Battery charging circuit The rechargeable batteries are charged via stabilized power supply 103 104 106 107 108 and via diode 105 The charging current corresponds to the float charge current of the batteries This current is relatively low and increases the charging time but the service life of the batteries is extended considerably Voltage monitoring for the batteries is not necessary Diode 110 protects the batteries from the unlimited current of the power supply unit 25 01 02 467 Index E Circuit description Model 717 727 728 737 748 757 Diode 102 is used as polarity reversal protection and overvoltage protection Diodes 110 and 111 protect against discharge during battery operation and against polarity reversal Electrolytic and tantalum capacitors are distributed evenly over the printed circuit board as backup capacitors for the operating voltage 08 02 98 Law Blatt 4 3 25 01 02 467 Index E segment digit driver driver start puls microcomputer serial comparator reference interface on charging i
18. sured when the start button is pressed replace transistor 128 otherwise replace microprocessor IC 520 Check the microprocessor oscillator The frequency measured at pins 18 and 19 of the microprocessor IC 520 must be 12 MHz If this is not the case replace the quartz If the scale still does not work replace the microprocessor Blatt 1 30 34 00 437 Index G Seca 717 727 728 737 748 757 3 Fault description Scale displays after starting bAtt is triggered if the input voltage falls below approx 6 V When the scale is operated on a plug in power supply unit make the following check The voltage at Z diode 102 must correspond to the power supply unit voltage If the voltage collapses there is a short circuit e g in diode 102 or the power supply unit is defective When the scale is operated only on rechargeable batteries i e without a power supply unit make the following check On seca 748 the voltage at capacitor 120 must be approx 9 V on seca 727 and seca 757 it must be approx 7 2 V If the voltage is different recharge or replace the rechargeable battery 4 Fault description Digit defective Check the driver transistor 201 205 At the base of the associated transistor there should be a square wave signal with an amplitude of approx 0 7 V and an offset of approx 4 V At the collector of the associated transistor there should be a square wave signal with an amplitude of app
19. the scale corresponds to the set display Ag 5 Remove the test weight from the scale and restart it Weight the scale with the test load and check if the display value corresponds to the set display tolerance 5 g If not repeat steps 5 and 6 described herein 6 Represent the scale for re calibration Take care thatthe holes for the rotary potentiometers are secured by protection marks against unauthorized use after re calibration INCLIN COARSE INCLIN FINE This procedure is suitable for adjusting model 757 too Dokument 00609_E1 DOC erstellt am 29 09 1998 seca 717A 717 japan 757 seca 717A 757 Spare parts list Item Article no Designation Price stage 01 02 01 01 252 008 Frame black 40 02 01 10 04 007 509 Levelling device 18 03 08 06 14 239 009 Battery compartment 20 04 08 04 05 336 009 PCB holder 04 05 08 06 16 058 119 Cable harness for rechargeable battery connection model 757 only 24 06 08 06 16 083 119 Cabel harness for RS 232 interface model 757 only 25 12 08 04 05 317 009 Screening plate bottom 15 13 08 06 16 104 119 Cable harness for mains connection 24 18 08 04 05 346 009 Cable duct model 717 only 20 19 66 30 02 030 009 Snap on spacer 01 20 08 06 18 014 009 Main board 48 08 06 18 094 009 Main board model 757 RS 232 only 49 08 06 18 014 509 Main board model 717 japan 48 22 02 03 01 249 009 Platform support 32 23
20. tion All digital functions of the A D converter are implemented via software in a microcomputer The reference potential of the A D converter is U 2 since the positive input of integrator 402 is connected to a bridge output via resistor 506 During a predefined total time T first the input voltage Ue is connected to integrator 402 via resistors 507 and 506 and then the reference voltage U 2 with FET switch 600 1 2 13 via resistors 510 517 for model 727 only 602 604 511 512 513 and 514 The components are selected so that the integrator integrates up during this phase whenever an input voltage is applied until comparator 502 reacts The response threshold of the comparator is determined by resistors 410 and 411 Resistor 413 causes positive feedback and prevents the comparator oscillating The microcomputer detects that comparator 502 is triggered and switches FET switch 600 1 2 13 off The integrator now runs down until time T has expired The interval between T 0 and the moment the comparator reacts is a measure for the input voltage Ue Trimmer 602 compensates for the local gravitation GAL value Trimmer 604 is used to fine adjust the slope As the adjustment range for 604 has been deliberately kept small the slope can be adjusted using the combination 513 514 08 02 98 Law Blatt 1 3 Resistors 508 or 509 which can be used alternatively are used for coarse adjustment of the zero point Resistor 412 helps the ou
21. tput stage of amplifier 402 to increase the negative output range Resistors 515 or 516 allow characteristic curves to be corrected For incubator scale 748 only For reasons of electromagnetic compatibility the analog to digital converter circuit is provided on a separate board Reducing the analog signal path by mounting the board in the base plate and using interference suppression capacitors 400 401 501 603 considerably reduce electromagnetic susceptibility The 5V supply voltage for the board is fused on the main board with 100mA fuse to limit the energy on the board in the event of a fault Temperature compensation For temperature compensation of the strain gauge sensor a fixed value resistor is connected in parallel with a temperature dependent resistor To compensate for the sensitivity s t c value the combination 511 512 is used NTC The positive t c value of the test value can be compensated for by the combination 405 406 PTC Zero point sensitivity and test value are partly interdependent To determine these values the modules electronics sensor are measured at 10 C and 40 C zero point slope test value and the results are entered into a computer The computer uses a complex computing routine to calculate the optimum temperature compensation Microcontroller and display The central computing and control element is the microcontroller uC 520 It fulfils the following functions Digital
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