Bosch TCA640 Series Repair Instruction page 86

7.5.3 Grinding unit is not functioning
Fault description:
Grinding unit is not running
Possible faults:
1. No control signal voltage from logic module
2. No voltage at power module grinding unit output
3. No voltage on the grinding unit
Troubleshooting:
1. Check control signal voltage from logic module
First check whether the logic module is relaying the signal required for
actuation of the grinding unit to the power module. To do this, open
the appliance. Using the Torx T10 screwdriver, unscrew all rear panel
screws and remove the rear panel. Remove upper appliance cover to
the rear. Remove both side panels upwards.
The control signal voltage can be measured on plug CL10 on
terminals 1 = GND (brown) and 5 = 5 VDC (green). The grinding unit
must be actuated by a coffee brewing process.
►
No signal voltage
defective
→
►
Voltage available
58300000120060_ARA_en_c.doc – 18.09.09
→
Logic module or connecting cable
see Point 2
2. Check voltage on power module grinding unit output
The voltage for the grinding unit is measured on plug CP6 on
terminals 3 = GND (black) and 2 = 230 VDC (transparent). The
grinding unit must be actuated by a coffee brewing process.
→
►
No voltage defective power module
→
►
Voltage available
3. Check voltage on grinding unit
The operating voltage for the grinding unit is measured on the
connecting plugs of the grinding unit. (Black = GND, transparent =
230 VDC). The grinding unit must be actuated by a coffee brewing
process.
→
►
No voltage defective wiring
→
►
Voltage available
see Point 3
defective grinding unit
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