16
BÜCHI
Vacuum Controller
B-720
6.4 Function check
The following parameters must be checked after every service
intervention:
•
Switch on the B-720
•
Display shows 8888 (1 sec.)
•
Display shows the software function A 1.1 (1 sec.)
•
Display shows the current atmospheric pressure
•
The valve is triggered audibly
•
The cooling water valve is open
6.5 Block diagram of the B-720
Membrane keypad
CPU print
Power print
Euro power plug
Ceramic pressure sensor
Ventilation valve
6 Maintenance
Figure 13: Block diagram of the B-720
Malfunction
Possible cause
Remedy
Valve opens and closes at high rate
System has a leak
Check all sealing points
Hysteresis too small
Select higher hysteresis value
Valve does not open or close
Valve does not close
Dirty coil
Wrong flow direction
Valve not inserted in the proper position
No display
Defective fuse
Replace fuse
Check power plug and insert
Error code E--3
Pressure sensor is defective
Replace pressure sensor
Error code E--4
Pressure differential too small during calibration
Increase pressure differential
sensor defective
Replace pressure sensor
Error code E--7
Pressure sensor not calibrated
Call service center
Error code E-10
Hardware error
Call service center
Table 8: Malfunction
6.6 Troubleshooting