Chapter 6 Control system diagram
SMSO-2-02.06- 15.07.03 193
6.5.11 Piston motor
36V 5V DC
36V S L1, N
Operating condition
When a “coffee” product button is pressed on the button panel, the piston motor on the brewing unit operates several times
briefly during a brewing cycle (note warming up time!)
Symptoms
Piston motor is not functioning.
Procedure (system test: “Move piston”
Process
step
Check Possible cause Remedy
1
Take voltage measurement at
plug X34 1/2 on power PCB:
+/-36 V DC ?
Check the voltage supply (see
“Power PCB, control voltage”)
Replace the power PCB
36V S voltage supply faulty
Piston motor control faulty (dis-
play message “piston motor time-
out”)
2
Take voltage measurement at
piston motor, according to direc-
tion of travel of brewing cylinder
(piston)
for +/- 36 V DC ge (yellow) wire
for +/- 36 V DC gn (green) wire
Plug contacts on power PCB
faulty / oxidised
Cable broken or pulled out of plug
Flat plug not correctly connected
Check / replace plug contacts
Replace cable
Re-connect the flat plug on the
plug-in contact stud
Resistance measurement at piston motor:
Switch off voltage
Pull out cable from plug-in contact studs
3
Carry out resistance measure-
ment at piston motor:
Nominal resistance:
< 10 Ω ?
Plug in contact studs oxidised
Piston motor defective
Replace the piston motor
The resistance measured at the piston motor differs according to the position of the motor, and can be up to approx.
10 Ohm
Re-connect the flat plug to the
piston motor. Function check: The
piston motor is functioning
NO
YES
NO
YES
NO
ES
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