Seca 334 LC User manual

for seca 334 LC / 335 LC
Service Manual
3341321008
3341321368
3357021094
3357021129
3357021159
Baby scale with 4 load cell technology
Valid as of: 01.04.2013
Variants:
Contents:
Description:
Service Manual Number
17-05-01-342-b
When servicing or repairing seca devices according to this service manual, always take note of the
instruction manual of the product. To download the latest version of the instruction manual and EMC
Recommendation go to www.seca.com.
Description electronic 30-34-00-864
Cableplan 08-02-06-036 a
Replacement 30-34-00-752 a
Spare parts 334 1321008
Spare parts 334 1321368
Spare parts 335 7021159
Spare parts drawing 30-34-00-749 b
EMC Recommendation 30-35-00-219
Instruction manual mod. 334 LC 17-10-06-335
Instruction manual mod. 335 LC 17-10-07-552
Instruction manual mod. 335 LC China 17-10-07-555
Manual number: 17-05-01-342-b

Service Instructions LC Electronics seca
03.04.2013/JEG 1 (24) 30-34-00-864
Service Instructions Electronics (LC)
MODEL
[334|335|382|383|384|385|769|799|780|833|834|835|869|899|874|
875|876|877|878|952|956]

Contents seca
03.04.2013/JEG 2 (24) 30-34-00-864
Contents
1General Information....................................................................................................................... 3
1.1Rating plates..................................................................................................................... 3
1.2Structure and function of scale section ............................................................................ 4
1.2.1Structure .............................................................................................................. 4
1.2.2Function............................................................................................................... 4
2Calibration of Scales ..................................................................................................................... 6
2.1Manual calibration of scale [334|335|382|383|384|385|833|834|835].............................. 6
2.2Manual calibration of scale [874|875|876|877|878|952|956]............................................ 9
2.3Manual calibration of scale [769|780|799|869|899]........................................................ 11
2.3.1Linear calibration ............................................................................................... 11
2.3.2Calibration of corner loading.............................................................................. 13
3Troubleshooting........................................................................................................................... 15
3.1Error symptoms scale..................................................................................................... 15
3.2Scale error messages..................................................................................................... 16
3.3Error messages [334|335|382|383|384|385|833|834|835|874|875|876|877|878|952|956]16
3.4Error messages [769|799|780|869|899]......................................................................... 17
4Measurements for Fault Localisation .......................................................................................... 19
4.1Power supply.................................................................................................................. 19
4.2Load cell ......................................................................................................................... 19
4.2.1Testing load cells with a multimeter................................................................... 19
5Replacing Electronics.................................................................................................................. 21
6Appendices.................................................................................................................................. 23

General Information seca
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1 General Information
These service instructions are for technicians responsible for the maintenance and repair
of devices. These persons must be familiar with all regulations governing electrical
engineering and comply with them in all cases. These instructions are not intended for
users without specialist skills.
These instructions describe servicing for the devices [334|335|382|383|384|385|769|799|
780|833|834|835|869|899|874|875|876|877|878|952|956]. The individual sections indicate
the devices to which they apply in each case.
1.1 Rating plates
To identify the exact model see the information and serial number on the underside or
base frame of the device (see Figure 1). Please take note of this data so you have it to
hand when making queries or ordering spare parts.
Figure 1: Rating plates

General Information seca
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(Modular cable)
LC weight calculation
08-06-18-149
Load
cell Load cell Load cell Load
cell
LCD module
08-06-18-147 Keypad
DC power
1.2 Structure and function of scale section
1.2.1 Structure
The scale basically consists of the following parts:
Base frame with up to four load cells
Display unit with keypad
Power supply (batteries, optional power pack)
.
1.2.2 Function
The effect of weight on the weighing surface causes elastic deformation of the load
cell(s) underneath. They produce an electronic analogue signal which shows linear
variation in relation to the application of force. This signal is measured by the weight
calculation system, analysed and displayed as a weighing value. Figure 2 shows the
function chart for scales with separate electronic modules for weight calculation and
display. Figure 3 shows the function chart for scales with one electronic module for
weight calculation and display.
Figure 2: Function chart [769|799|780|869|899]

General Information seca
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LC compact modules (weight
calculation and display)
08-06-18-142 or 08-06-18-160
Load
cell Load
cell Load cell Load cell
Keypad
DC supply
Figure 3: Function chart [334|335|382|383|384|385|833|834|835|874|875|876|877|878|952|956]

Calibration of Scales seca
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2 Calibration of Scales
The scale is equipped with a calibration option to compensate for linear measurement
errors as for example, those occurring with geographical variation in the earth's
gravitational force. This calibration procedure must also be carried out whenever a load
cell is replaced.
Calibration can be performed in one of two ways:
The scales are equipped with an internal manual calibration feature, which is
regulated by the control elements on the device.
Calibration is performed with the help of seca serva
2.1 Manual calibration of scale [334|335|382|383|384|385|833|834|835]
Manual calibration is activated by plugging a jumper on the printed circuit board (see
Figure 4). These contacts are only accessible after breaking the seal and opening the
scale. After plugging the jumper, the scale has to be switched on to start manual
calibration.
Figure 4: Jumper contacts to activate manual calibration

Calibration of Scales seca
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The following steps are necessary to perform manual calibration of the scale:
1. Switch on the scale and check the battery charge (see note). Calibration
must not continue if the batteries are low!
2. Then switch the scale off and unscrew the lower service lid after having
removed the seal.
3. Connect the two jumper contacts using a jumper.
4. Then set up the scale properly again and switch on.
5. Start-up of the scale is followed by the segment test and then a flashing
display showing the weight to be placed on the scale.
6. Place the calibrated weight in the middle of the weighing surface in one,
or at most two steps of equal size. The calibration weight required may
vary depending on the model (see Table 1).
Model Calibration weight
335, 382, 384 10 kg
334, 384, 833, 834 15 kg
835 20 kg
383, 385 40 kg
Table 1: Calibration weights required
7. Once a correct, stable weight value is identified, the LCD display will
stop flashing, and a calibration value will be calculated and stored. The
scale then switches off automatically shortly afterwards. If the LCD
display does not stop flashing, the measured weight is either above or
below the weight to be expected, or a stable weight value cannot be
established (due to vibration / shocks, etc.).

Calibration of Scales seca
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8. Then remove the weight from the scale, detach the jumper from the
PCB and replace the service lid.
9. Now set up the scale again and switch on. Next, place a calibrated
weight on the scale and check the display for the correct weight value. If
manual calibration was successful, reseal the service lid according to
the national regulations.
Note:
Automatic monitoring of the battery voltage is not possible during manual calibration. It
should therefore be checked before and after every calibration procedure. This can be
carried out by switching on the scale and observing the display. If the battery voltage is
insufficient, either the battery warning symbol or the "bAtt" display will be activated. If one
of these displays appears before or immediately after calibration, the batteries should be
replaced and the calibration procedure repeated.
Manual calibration can be aborted before placing the required weight on the scale by
switching off the device.

Calibration of Scales seca
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2.2 Manual calibration of scale [874|875|876|877|878|952|956]
Manual calibration is activated using a sliding switch (SJ1) on the PCB (see Figure 5). It
is only accessible after breaking the seal and opening the scale. After changing the
switch position to 2 ("CAL"), the scale has to be switched on to start manual calibration.
Figure 5: Slide switch to activate manual calibration
The following steps are necessary to perform manual calibration of the scale:
1. Switch on the scale and check the battery charge (see note). Calibration
must not continue if the batteries are low!
2. Then switch the scale off and open the integrated display by releasing
the four screws after having removed the seals.
3. The position 2 ("CAL") must be selected with the slide switch on the
PCB, which is now accessible.
4. Then set up the scale properly and switch on.
5. Start-up of the scale is followed by the segment test and then a flashing
display showing the weight to be placed on the scale.

Calibration of Scales seca
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6. Place the calibrated weight in the middle of the weighing surface in one,
or at most two steps of equal size. The calibration weight required may
vary depending on the model (see Table 2).
Model Calibration weight
874, 875, 876, 877, 878,
952, 956 120 kg
Table 2: Calibration weights required
7. Once a correct, stable weight value is identified, the LCD display will
stop flashing, and a calibration value will be calculated and stored. The
scale then switches off automatically shortly afterwards. If the LCD
display does not stop flashing, the measured weight is either above or
below the weight to be expected, or a stable weight value cannot be
established (due to vibration / shocks, etc.).
8. Then remove the weight from the scale, move the slide switch on the
PCB back to its original position and refit the display.
9. Now set up the scale again and switch on. Next, place a calibrated
weight on the scale and check the display for the correct weight value. If
manual calibration was successful, reseal the scale according to the
national regulations.
Note:
Automatic monitoring of the battery voltage is not possible during manual calibration. It
should therefore be checked before and after every calibration procedure. This can be
carried out by switching on the scale and observing the display. If the battery voltage is
insufficient, either the battery warning symbol or the "bAtt" display will be activated. If one
of these displays appears before or immediately after calibration, the batteries should be
replaced and the calibration procedure repeated.
Manual calibration can be aborted before placing the required weight on the scale by
switching off the device.

Calibration of Scales seca
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2.3 Manual calibration of scale [769|780|799|869|899]
Manual calibration is activated either by plugging a jumper or with newer models, by
actuating a sliding switch on the printed circuit board (see Figure 6). These contacts are
only accessible after breaking the seal and opening the scale. After plugging the jumper
or actuating the sliding switch, the scale has to be switched on to start manual
calibration. Depending on the subsequent loading method (in the centre or a corner of
the weighing surface) either linear calibration of the scale is performed or calibration of
corner loading, which is essential when a load cell is replaced.
Figure 6: Jumper contacts or slide switch to activate manual calibration
2.3.1 Linear calibration
The following steps are necessary to perform manual calibration:
1. Switch on the scale and check the battery charge. If the battery voltage
is insufficient, either the battery warning symbol or the "bAtt" display will
be activated. If one of these displays appears before, during or
immediately after calibration, the batteries should be replaced and the
calibration procedure repeated.
2. Then switch the scale off and open the display housing by releasing the
four screws after having removed the seals.

Calibration of Scales seca
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3. The position 2 ("CAL") must be selected with the slide switch on the
PCB, which is now accessible, or with older models, the two jumper
contacts have to be connected using a jumper.
4. Then set up the scale properly and switch on.
5. After start-up of the scale the segment test is followed by a flashing
message on the display reading "LOAd".
6. Place the calibrated weight in the middle of the weighing surface in one,
or at most two steps of equal size. The calibration weight required may
vary depending on the model (see Table 3).
Model Calibration weight
769, 780, 799, 869, 899 120 kg
Table 3: Calibration weights required
7. Once a centred load is identified on the weighing surface, the display
will read "CAL L". A few seconds later it starts to flash, showing the
weight to be placed on the scale.
Note:
If the display reads "CAL E", a corner load has been identified. In this
case the weight must be removed and the procedure aborted by
switching off the scale. Check correct set-up of the scale and repeat
linear calibration (from item 4.)
8. The weighing value displayed should now be acknowledged by briefly
pressing any key (except the Start key). Once a stable weight value is
identified, the LCD display will stop flashing, and a calibration value will
be calculated and stored. Shortly afterwards the LCD display will read
"Sto", and the scale switches off automatically a few seconds later.
9. Then remove the weight from the scale, move the slide switch on the
PCB back to its original position or remove the jumper and reassemble
the display housing.

Calibration of Scales seca
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10.Now set up the scale again and switch on. Next, place a calibrated
weight on the scale and check the display for the correct weight value. If
linear calibration was successful, reseal the display housing according
to the national regulations.
2.3.2 Calibration of corner loading
Recalibration of corner loading is necessary when a load cell is replaced.
The following steps are necessary to perform manual calibration of corner loading:
1. Switch on the scale and check the battery charge. If the battery voltage is
insufficient, either the battery warning symbol or the "bAtt" display will be
activated. If one of the two displays appears before, during or immediately
after subsequent corner correction, the batteries should be replaced and
subsequent corner correction repeated.
2. Then switch the scale off and open the display housing by releasing
the four screws after having removed the seals.
3. The position 2 ("CAL") must be selected with the slide switch on the
PCB, which is now accessible, or with older models, the two jumper
contacts have to be connected using a jumper.
4. Then set up the scale properly and switch on.
5. After start-up of the scale the segment test is followed by a flashing
message on the display reading "LOAd".
6. Place the calibrated weight on the corner where the load cell was replaced in
one, or at most two steps of equal size. The weights required may vary
depending on the model.

Calibration of Scales seca
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7. Once a corner load is identified on the weighing surface, the display will read
"CAL E", followed by "E 1". A few seconds later it starts to flash, showing the
weight to be placed on the scale.
Note:
If the display reads "CAL L", a centred load has been identified. In this
case the weight must be removed and the procedure aborted by
switching off the scale. Check correct set-up of the scale and repeat
linear calibration (from item 4.)
8. The correct weight should now be acknowledged by briefly pressing any key
(except the Start key). Once a stable weight value is identified, the LCD
display will stop flashing and will read "UP".
9. Then remove the weight from the scale. Once removal of the weight is
detected, the display will read "E 3", A few seconds later it starts to flash,
showing the weight to be placed on the scale. The weight displayed should
now be placed in the corner diagonally opposite to corner 1 and
acknowledged by briefly pressing any key (except the Start key). Once a
stable weight value is identified, the LCD display will stop flashing, and a new
corner correction value will be calculated and stored. Shortly afterwards the
LCD display will read "Sto", and the scale switches off automatically a few
seconds later.
10.Then remove the weight from the scale, move the slide switch on the
PCB back to its original position or remove the jumper and
reassemble the display housing.
11.Now set up the scale again and switch on. Next, place a calibrated weight on
the individual corners and check the display for the correct weight value. If
subsequent corner correction was successful, reseal the display housing
according to the national regulations.

Troubleshooting seca
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3 Troubleshooting
The following section contains an overview of possible error symptoms, their cause and
the steps required to remedy them. The error messages generated by the device itself
are also described below as well as the options for rectifying them.
3.1 Error symptoms scale
Description of
error Possible causes Remedy
Power supply defective Check batteries and/or
power pack (if present)
Voltage supply defective Check cabling (see
section 4)
Scale does not start
Keypad defective or not
connected
Check cable
connections, check
cabling and keypad for
disconnection, replace if
necessary
Packaging / transport lock not
completely removed Check scale
Scale not calibrated Recalibrate scale (see
section 2)
Load cell damaged Replace load cell
Scale either
showing wrong
weight or none at all
Application of force to load
cell interrupted Check load cell connections
Replace electronics unit
Wide variation in
measured values Electr. measuring unit/load cell damaged Replace load cell

Troubleshooting seca
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3.2 Scale error messages
The scales have an error message feature which indicates possible malfunctions and
defects. These error messages are described below.
3.3 Error messages
[334|335|382|383|384|385|833|834|835|874|875|876|877|878|952|956]
If a malfunction or defect occurs during operation of the scale, it is shown on the display
as an error message. Error messages are displayed in the following form:
"E xx"
E: Error
xx: Error number (see Table 4)
Displayed Cause Remedy
E 11
Load cell defective, supply
leads damaged or electronics
defective
Diagnosis with seca serva:
Check load cell connections
Poss. replace load cell or
electronics
Check preload on scale
E 12 Preload too great, load cells damaged or electronics
defective Diagnosis with seca serva:
Poss. replace load cell or
electronics
E 13 Limit for automatic zero tracking
reached Place load of >0.5d/s on scale
E 16 Error when determining zero
point on switch-on Protect scale from vibration / shocks during start-up

Troubleshooting seca
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seca serva: Recalibrate scale
E 40 EEPROM data incorrect Replace electronics
Table 4: Error messages [334|335|382|383|384|385|833|834|835|874|875|876|877|878|952|956]
3.4 Error messages [769|799|780|869|899]
If a malfunction or defect occurs during operation of the scale, it is shown on the display
as an error message. Error messages are displayed in the following form:
"E mm.xx"
E: Error
mm: Number of the module reporting the error
(10 = weight calculation, 11 = electronic display)
xx: Error number (Table 5)
Displayed Cause Remedy
E XX. 11
Load cell defective, supply
leads damaged or electronics
defective
Diagnosis with seca serva:
Check load cell connections
Poss. replace load cell or
electronics
Check preload on scale
E XX.12 Preload too great, load cells damaged or electronics
defective Diagnosis with seca serva:
Poss. replace load cell or
electronics
E XX.13 Limit for automatic zero tracking
reached Place load of >0.5d/s on scale

Troubleshooting seca
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E XX.16 Error when determining zero
point on switch-on Protect scale from vibration / shocks during start-up
seca serva: Recalibrate scale
E XX.40 EEPROM data incorrect Replace electronics
E XX.60 Communication error
Check modular cable between
display and weight
determination system
Table 5: Error messages [769|799|780|869|899]

Measurements for Fault Localisation seca
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4 Measurements for Fault Localisation
The following section contains an overview of measurements that can be made for
specific fault localisation.
4.1 Power supply
Measurement of the power supply to the PCB indicates whether the leads from the
battery compartment and/or power pack are defective. A multimeter is used for
measurement at the measuring points B (see Appendix).
4.2 Load cell
The most effective method for establishing a defect in the load cell is to use the seca
serva diagnostic function. If this is not available, another option is to use a multimeter.
Measurement with a multimeter is however not as conclusive, so this method should
always be second choice here.
4.2.1 Testing load cells with a multimeter
The load cell is first unsoldered from the electronics and the ohmic resistance between
the different connecting wires measured using a multimeter. The following tables show
the values to be expected for the various load cells:
Measurement between Ohmic resistance [Ω]
V+and Sig- (green and red) ~ 800-850
V+and Sig+ (green and white) ~ 800-850
V-and Sig- (black and red) ~ 800-850
V-and Sig+ (black and white) ~ 800-850
Sig+/Sig-/V+/V- and aluminum body
of load cell > 500 M
Table 6: Load cell resistances
[334|335|382|383|384|385|833|834|835|874|875|876|877|878|769|799|780|869|899]