Seca 769 LC User manual

for seca 769 LC / 780 LC gost/ 799 LC
Service Manual
769 1321004
769 1321994
780 2321369
7997021099
7997021159
Colum scale with 4 load cell technology
Valid as of: 01.12.2010
Variants:
Description LC2 electronic 30-34-00-745
Content:
Function diagram 25-02-02-281
Adjustment model spezific options 30-34-00-743
Description of faults 30-34-00-744
Cableplan 08-02-06-037 a
Spare parts 30-34-00-746 b
Description:
Service Manual Number
17-05-01-340-b
Manual number: 17-05-01-340-b

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 1(6)30-34-00-745
Brief description of the LC display module
Introduction
The display module belongs to the LC family of seca’s electronic modules and is used to indicate a
weight value measured with the LC weight module and supplied via the module bus. The display
module also accommodates the operating elements and can process the weight (hold, tare, etc.).
Furthermore, a simple switch/jumper is provided to activate scale service.
The following block diagram shows the main function blocks of the LC display module:
Voltage
regulation uC
LCD
Operation
Programming
interface
LC module bus
Scale
service
Switch
on/off
logics
Display representation
A maximum of five digits as well as some special characters can be displayed, which can appear as
shown below:
Explanation of the special characters:
Symbol Meaning
Battery Battery warning, operation of the scale can continue, but the batteries
should be replaced. If the batteries are not replaced and are allowed to
discharge below the next threshold, the ”bAtt“ message is displayed.
Measurements are then no longer possible.
Measuring range 1 Measuring range 1 is active.
Measuring range 2 Measuring range 2 is active.
Power supply unit The scale is operating in power supply unit mode.
PT PT indicates that a weight value previously saved will automatically be
subtracted from the weight value currently measured.
BMI The BMI function is active. Once body height has been entered, the BMI
value is displayed.

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 2(6)30-34-00-745
Hold + warning
triangle Hold indicates that the weight display has frozen. The warning triangle signals that the weight displayed on the scale is not verifiable.
TARE, NET Tare or Net show that a weight on the scale has been tared out.
cm The value displayed corresponds to body height in cm. (BMI)
lbs The weight value is displayed in lbs.
kg The weight value is displayed in kg.
sts The weight value is displayed in lbs and sts.
Power supply
Power supply is provided via the LC module bus. The power supply for the display module is
connected through the start button. Once the microcontroller on the LC display module has started, it
assumes control of the power supply. When the start button is pressed again, the power supply to the
display is switched off.
Operation
With the exception of the start button (if provided), the connected buttons can be configured as
required for the particular model. These buttons can be pressed just lightly or longer (longer than 1 s).
Scale service
To activate scale service, 2 contact pins on the PCB must be short-circuited by means of a
jumper/switch. Access to these contacts can only be gained by destroying the seal and opening the
display housing. After placing the jumper, switch on the scale to start scale service.
LC module bus
The LC module bus establishes the connection to the LC weight module. The unregulated supply
voltage from the LC weight module is available on the bus. All relevant data is exchanged via a data
line and a clock pulse line.
Pin Function Note
1SCL Serial Clock TWI
2GND Ground
3SDA Serial Data TWI
4Vin Battery/power supply voltage
Programming interface
The programming interface is a 10-pin interface, which is only accessible after opening the display
housing. The display housing is secured with a seal that must be destroyed to open the housing.
Warning: If the seal is destroyed, verification is no longer valid. A special seca service adapter is
required to access the programming interface.
The service interface can be used to:
-supply the unregulated supply voltage
-measure the regulated voltage for the electronics
-execute the start function
-delete and write new data to the flash memory and the EEPROM of the microcontroller
Programming
The microcontroller contains two types of non-volatile memories that are used for various purposes in
the module.
The following memory types are provided:

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 3(6)30-34-00-745
Type of memory Size
Flash memory 8 Kbytes
EEPROM 512 bytes
The flash memory holds the firmware for the microcontroller. During programming, the data is written
to the flash memory via the 10-pin programming interface. The parameters read out by the LC display
module from the LC weight module after being set into operation for the very first time are stored in the
EEPROM. Both memories are protected by an LRC checksum. A data error in either of the two
memories cannot be remedied during the operation and causes a permanent fault indication.
Weighing operations are then no longer possible. Once the scale has been programmed, both
memories are protected against reading out and modifying data via the programming interface. Any
modification of the data first requires that both memories are completely cleared.
Fault handling
If faults occur, they are displayed on the LCD with the relevant fault code. Each fault message
includes the number of the module type on which the fault has occurred.
Module Number
LC weight module 10
LC display module 11
The following fault messages are implemented:
Fault number Fault description
11 Outside value range (positive or negative overload)
12 Switch-on zero point outside the permissible range
13 Zero follow-up outside the permissible range
16 No zero point
40 EEPROM checksum fault
50 Flash memory checksum fault
60 Bus communication fault
Technical data
Supply voltage :9V –12V (via LC module bus)
Supply current: typ. 11.8mA
Zero-signal current: typ. < 0.1µA
Operating temperature: approx. 0°C to 50°C
Storage temperature: -10°C to 60°C
Dimensions: 63mm x 42mm x 1.7mm

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 4(6)30-34-00-745
Brief description of the LC weight module
Introduction
The LC weight module is used to determine weights using one or several load cell(s) with strain
gauges. The LC module bus supplies the processed measured values to the LC display module.
The following block diagram shows the main function blocks of the LC weight module:
Voltage
regulation uC
Voltage
measurement
A/D converter
Programming
interface
LC module bus
Switch
on/off
logics
Load cell(s) Temperature
measurement
Resonator
Mains
connection
/battery
Weight measurement
The weight module uses load cells with strain gauges in a double bridge circuit as sensors. The entire
analog part and the load cells, as well as the other peripherals, are supplied with a 5V supply voltage.
At full load, the load cells supply a bridge output voltage of 0.8mV/V. This voltage is measured by a
dual slope A/D converter; the different voltages supplied by the four load cells are multiplexed
accordingly. Every 500 ms, 12 measurements are carried out per load cell and the mean value is then
calculated. Before the mean values for each load cell are merged and converted into the weight value,
an individual corner correction factor is applied to them. A linear function is used to convert the results
into a weight value. The first stable value within the switch-on zero setting range after switching on the
scale is used as zero point. The zero follow-up range is monitoring during the operation of the scale.
Temperature measurement
In order to compensate for the load cell’s temperature drift, the temperature is measured regularly and
the measured value is adjusted accordingly. For this measurement, the voltage is cyclically measured
via an NTC, which forms a voltage divider together with a linearization resistor connected in series. To
reduce measured value fluctuations, amean value of 8 temperature values is always formed.
Fluctuations are thus reduced to a third compared with individual measurements. The difference
between the current temperature and the temperature measured when the last zero point was
obtained is used to determine a projected zero point. To do so, one assumes that the weight change
per °C is constant. The weight value is then corrected in accordance with the zero point calculated and
in accordance with the difference to the temperature measured when the scale was adjusted.
Power supply
Power supply can be provided by AA size batteries or a power supply unit. The circuit cannot be
operated on rechargeable batteries. The unregulated voltage is connected to a 5V in-phase regulator
via reverse voltage protection diodes. The regulated 5V supply voltage is then available to the entire
circuit. The supply voltage for the analog part can be switched separately from the rest of the PCB via
a switch on/off logic. The digital part is permanently supplied with 5V.
Voltage measurement
To enable power supply unit and battery operation to be distinguished and in order to measure the
current battery voltage, the unregulated voltage is monitored by the microcontroller. Voltage
measurement takes place via a voltage divider and by means of the internal A/D converter.

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 5(6)30-34-00-745
If the voltage drops below a certain limit, the user is alerted by the battery symbol in the LCD. If the
next threshold is undershot, "bAtt” is displayed and weighing is no longer possible.
Resonator
A ceramic 8 MHz resonator is used as a time basis for all functions of the module.
LC module bus
The LC module bus establishes the connection to the LC display module and at the same time forms
the adjustment interface. The unregulated supply voltage is made available on the bus. All relevant
data is exchanged via a data line and a clock pulse line.
Pin Function Note
1SCL Serial Clock TWI
2GND Ground
3SDA Serial Data TWI
4Vin Battery/power supply voltage
Programming interface
The programming interface is a 10-pin interface, which is only accessible after opening the housing.
The housing is secured with a seal that must be destroyed to open the housing. Warning: If the seal is
destroyed, verification is no longer valid. A special seca service adapter is required to access the
programming interface.
The service interface can be used to:
-supply the unregulated supply voltage
-measure the regulated voltage for the electronics
-delete and write new data to the flash memory and the EEPROM of the microcontroller
Programming
The microcontroller contains two types of non-volatile memories that are used for various purposes in
the module. The following memory types are provided:
Type of memory Size
Flash memory 8 Kbytes
EEPROM 512 bytes
The flash memory holds the firmware for the microcontroller. During programming, the data is written
to the flash memory via the 10-pin programming interface. All scale-specific parameters required by
the display and for measuring the weight are stored in the EEPROM. Data is written to the EEPROM
during the adjustment process. The display automatically retrieves all the parameters it needs from the
EEPROM of the LC weight module via the LC module bus. Both memories are protected by an LRC
checksum. A data error in either of the two memories cannot be remedied during the operation and
causes a permanent fault indication. Weighing operations are then no longer possible. Once the scale
has been programmed, both memories are protected against reading out and modifying data via the
programming interface. Any modification of the data first requires that both memories are completely
cleared.
Adjustment
To ensure that the scale functions properly, the LC weight value module must be adjusted before it is
set into operation. During the adjustment, the A/D converter supplies measured values to the
adjustment processor via the LC module bus. The adjustment processor determines the adjustment
data for the LC weight module from the values measured for different loads on the scale. If you wish to
configure individual temperature compensation, the scale must be measured with a load and without a
load at temperatures on different ends of the range. The adjustment data is then stored on the
EEPROM.

Service Manual Description of the LC2 electronics
23.07.07 Kr/Rei Page 6(6)30-34-00-745
Scale service
The electronics offer the following service functions:
To be able to compensate for linear measuring errors of the scale, resulting e.g. from different forces
of gravity at different geographical points, the module has a recalibration function. When the
recalibration function is started, the display shows the weight to be placed on the scale. Place the
weight in the centre of the scale and acknowledge this action via the keyboard. Once a stable weight
value has been identified, the correction factor is calculated and stored in the EEPROM. After
recalibration, the scale switches off automatically. The recalibration function can be aborted by
switching the scale off before the requested weight has been acknowledged.
The module has a function for subsequent corner correction, so that it is not necessary to re-adjust the
entire scale if a load cell is replaced. To carry out subsequent corner correction, two loads with the
requested weight must be placed on the scale in succession at the corners displayed. Loading must
be acknowledged. A new correction factor for the replaced load cell is calculated from the measured
values and is then stored in the EEPROM. After subsequent corner correction, the scale switches off
automatically. The subsequent corner correction process can be aborted by switching the scale off
before the weight placed on the scale for the second corner has been acknowledged.
Please refer to the adjustment and calibration instructions for further details regarding the individual
service functions.
Technical data
Supply voltage: 9V –12V
Supply current: typ. 32.5mA
Zero-signal current: typ. 120µA
Operating temperature: approx. 0°C to 50°C
Storage temperature: -10°C to 60°C
Dimensions: 92mm x 45mm x 1.7mm

Service manual Calibration
12.02.08 /Kr , Rei 1(2)30-34-00-743_E1
1. Recalibration instructions mod. 769 / 780 / 799 / 869 / 899
1.1 General
To compensate linear measuring deviations, which occur e.g. as a result of gravity variations in
different gravity zones, has the scale a recalibration function. The recalibration function is activated
either by plugging in a jumper or, on newer models, using a slide switch on the PCB Access to these
contacts can only be gained by destroying the seal and opening the scale. After placing the jumper or
activating the slide switch, the scale must be switched on to start the recalibration function.
1.2 Recalibration
Moduletyp LC-2-module.
1.2.1 Carrying out a recalibration
To carry out a recalibration, the following steps are required:
1. Switch on the scale and check the battery status. If the battery voltage is low, either
the early battery warning symbol or the "bAtt" display is activated. If one of the two
displays occurs before, during or immediately after recalibration, the batteries must be
replaced and recalibration must be repeated.
2. Then switch off the scale and open the display housing by unscrewing the four
screws.
3. This allows access to the slide switch on the PCB, which can now be operated..
4. Set the scale up properly again and then switch it on.
5. After starting the scale, the segment test comes up and then the text "LOAd" flashes
on the display.
6. Place the verified weight in the middle of the weighing platform. Do this in one step,
but not in more than two steps with equal loads. Depending on the model, the
necessary recalibration weights can have different sizes. ( cp. Table 1).
Model Recalibration weight
769, 780, 799 120 Kg
899 120 Kg
Table 1: Recalibration weights

Service manual Calibration
12.02.08 /Kr , Rei 2(2)30-34-00-743_E1
7. Once the scale has identified the load in the middle of the weighing platform, "CAL L"
comes up on display and, some seconds later, the display starts flashing to request
that a load be placed on the scale. The correct weight must now be acknowledged by
briefly pressing any of the buttons (with the exception of the start button). Once a
stable weight value has been recognized, the LCD stops flashing and a calibration
value is calculated and saved. Shortly afterwards, the text "Sto" is displayed on the
LCD and the scale automatically switches off some seconds later.
8. Then remove the weight from the scale, return the slide switch on the PCB to its
original position and re-assemble the display housing.
9. Now set the scale up again and then switch it on. Afterwards, place a calibrating
weight on the scale and check whether the correct weight is displayed. If recalibration
was successful, secure the display housing again with a seal in accordance with
national regulations.
1.2.2 Aborting a recalibration
The recalibration function can be aborted by switching the scale off before the requested weight has
been acknowledged

Service Manual Description of faults
19.07.07 /Kr/Rei 30-34-00-744
Scales with LC electronic
Please refer to the operating instructions to ensure that the scales were operated in the
proper manner. In case of a malfunction, the following table will help you to locate the fault.
Description of the fault Possible cause Remedy
Scales cannot be started •Battery is not
installed or
discharged
•Check the batteries
•Voltage supply is
defective •Check the voltage at the appropriate connections of the electronics; eliminate the interruption
•Bus connection
cable is defective •Check the plug-in connections; check the cables for interruption and replace them if necessary.
•Keypad is defective
or not connected •Check the cable connections; check the cables and the keypad for interruption and replace them if necessary
•Bus fault •Disconnect power supply unit and battery from the scale, wait for 60
seconds, then reconnect.
Scales show no weight or
an incorrect weight
(repeatedly)
•Packaging /
transport safeguard
has not been fully
removed
•Check the scales
•Scales are
maladjusted •Recalibrate the scales
•Sensor is damaged •Replace the sensor and start an additional corner override
transfer of force to the
sensor is interrupted
•Check the base frame for damage or incorrect assembly
Scale shows only the
segment test or the
readings are varying to
much.
•Shortcircuit between
sensor cable and
housing
•Search for damaged isolation of the cabel and repair it. ( If
appropriated use multimeter.)
Incomplete digits •Display is defective •Replace the electronics
Malfunction during the
weighing procedure •Display:
Er:x:no
•The electronics have detected an error.
nX:module number
nNo: error number
E XX.11
•Sensor is defective or
supply lines are
damaged
•Check connection cables, check sensor and replace as required (if
parts a replaced, a corner override is necessary)
•If several load cell are used, check the allocation (colour codes)
E XX.12
•Failure at
Identification
initial zero setting
•Check the initial load
•Sensor defective, replace it possibly (a corner override is
necessary)
E XX.13
•Limit for zero
tracking is reached •Load the scale at work with >50g/s
E XX.16
•Failure at
Identification
initial zero setting
•while the start process beware the scale for agitation
E XX.40
•No EEProm data •Recalibrate the scale
E XX.50
•Flash memory
damaged •Replace the electronics
E XX.60
•Bus connection
cable is defective•Check the plug-in connections; check the cables for interruption and replace them if necessary, Disconnect power supply unit and
battery from the scale, wait for 60 seconds, then reconnect.

Service Manual Spare parts list
seca 769 LC / 799 LC electronic
Item Articel-no. Designation Price stage
23.11.2010/Rei 1 30-34-00-746b
Baseframe drawing page 3,
01 02-01-03-386-509 Frame complete, calibrated mod.769 / 780 42
02-01-03-392-509 Frame complete, calibrated mod. 799 42
02 01-13-05-002-009 Foot complete mod. 769 / 780 05
01-10-04-007-009 Foot complete for levelling mod. 799 10
03 02-03-03-298-807 Platform 25
04 01-13-04-223-009 Platform mat 20
05 08-06-14-239-009 Battery compartment 15
06 66-30-60-010-009 Battery holder 10
07 02-11-03-011-009 Roller complete 18
08 02-01-03-130-509 Column connection complete 26
09 01-13-05-270-009 Plug white 01
10 02-01-03-383-009 Counter plate 10
11 08-06-12-249-009 Load cell 28
12 01-17-01-204-009 Bubble level 15
Display housing drawing page 4
21 04-02-06-215-008 Column painted 34
22 34-02-01-001-009 Display housing 26
23 34-02-04-394-009 Membrane keyboard mod. 769 / 780 25
34-02-04-404-009 Membrane keyboard mod. 799 25
34-02-04-405-009 Membrane keyboard mod. 799 China 25
34-02-04-417-009 Membrane keyboard mod. 799 Japan 25
24 08-04-04-195-509 LC display pre-assembled 37
for mod. 769 from ser. no. 5 769 184 07 XXXX
to ser. no. 5 769 349 07XXXX
for mod. 780 from ser. no. 5 780 184 07 XXXX
to ser. no. 5 780 349 07 XXXX
08-04-04-195-009 LC display pre-assembled (new software) 37
for Mod. 769 models from ser. no. 5 769 350 07 XXXX
for Mod. 780 models from ser. no. 5 780 350 07 XXXX
for Mod. 799 all models
for Mod. 869 all models
25 34-02-01-262-009 Connection piece left 02
26 34-02-01-263-009 Connection piece right 02
27 14-05-01-917-509 Sticker for window Mod. 769 / 780 05
14-05-08-220-509 Sticker for window Mod. 799 05
14-08-08-240-509 Sticker for window Mod. 799 Japan 05
08-06-16-142-119 Modular cable 1,0 m, 4-pole 15

Service Manual Spare parts list
seca 769 LC / 799 LC electronic
Item Articel-no. Designation Price stage
23.11.2010/Rei 2 30-34-00-746b
Mearuring rod drawing page 5
38 19-17-02-218-009 Headpiece tongue 22
39 19-17-02-219-009 Headpiece plate 20
40 19-17-01-324-009 Sliding block 19
41 19-17-02-211-009 Slide guide left 03
42 19-01-02-212-009 Slide guide right 03
43 19-17-01-284-009 Upper guide 08
19-17-03-032-009 Fixing material with long bush 12
18-01-07-053-509 Carton compl.. 28
18-01-01-674-009 Carton 20

01
12
ALL RIGHTS CONCERNING THIS DOCUMENT AND ITS
aErstellt / DRAWN
87654321
F
E
D C
B
A
45678
A
B
C D
E
F
Ersatzteilliste Mod. 769LC/799LC Untergestell
3534
Index / REVISION:
Blatt/SHEET 3/4
Freitag, 8. Januar 2010 15:14:50
b
HAMBURG Geprüft / APPROVED Ver. b
Datum/Name:
PROJECTION
R:\Archiv_DBWORKS\Firma\30-\30-34-\30-34-00-746-03
Änd.Mitteil. / CHANGE:
1:2
CONTENTS RESERVED. Alle Rechte an und aus diesen
Spare parts list mod. 769LC/799LC baseframe
Werkstoff / MATERIAL :
08.01.2010 Rein.
Unterlagenverbleiben seca gmbh. & co. kg.
30-34-00-746-03
Nr. / NO. :
25.07.2007
Benennung / TITLE :
reinhold
07.02.2008 Rein.
Pos. hinzu
Maßstab / SCALE :
11
05
08
09
F
F
02
03
04
07
06
F-F
1 : 1
10

26
24 25
21
23
27
seca gmbh. & co. kg.
Änd.Mitteil. / CHANGE: Index / REVISION:
87654321
5
678
A B C D E F
B C D E F
Maßstab / SCALE : Werkstoff / MATERIAL : Benennung / TITLE :
CONTENTS RESERVED. Alle Rechte an und aus diesen
pos. hinzu
Spare parts list mod. 769LC/799LC 30-34-00-746-04
R:\Archiv_DBWORKS\Firma\30-\30-34-\30-34-00-746-04
Freitag, 8. Januar 2010 15:09:57
Blatt/SHEET 4/4
Geprüft / APPROVED Ver. b
Erstellt / DRAWN PROJECTION
25.07.2007
Nr. / NO. :
ALL RIGHTS CONCERNING THIS DOCUMENT AND ITS
1:2
reinhold
HAMBURG
Ersatzteilliste Mod. 769LC / 799LC
a
Unterlagen verbleiben
07.02.2008 Rein.
b
08.01.2010 Rein.
3534
Datum/Name:
22