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
03.04.2013/JEG 3 (24) 30-34-00-864
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
03.04.2013/JEG 4 (24) 30-34-00-864
(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
03.04.2013/JEG 5 (24) 30-34-00-864
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
03.04.2013/JEG 6 (24) 30-34-00-864
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
03.04.2013/JEG 7 (24) 30-34-00-864
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
03.04.2013/JEG 8 (24) 30-34-00-864
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.