Owner's manual

7/8
Test of signal converter 7.6
Always switch off power source before opening the housing !
Re
quired measuring instruments and tools
Multimeter, DC and AC voltage, > 20 kohms / V
Crosstip screwdriver
Preparatory work Measuring and test points on
• Switch off power source. amplifier PCB, see Sect. 8.9
• Remove transparent cover (unscrew 4 MP = measuring point
recessed head screws) and black plastic TP = test point
cover (unscrew 1 recessed head screw), X1 = socket connector, 20-pin
see Fig. A and B in Sect. 8.5. X3, X5 = plug connector
• If provided, remove display PCB,
see Sect. 8.7.
• Switch power source on again.
Please note: When carrying out measurements, do not produce any short-circuits between the
components !
Action Typical result Faulty result
Voltage measurements on
amplifier PCB, see Sect. 8.9
1 between TP 1 (solder pin) 15 . . . 30 V DC
and Pin 11 of X1
2 between TP 1 (solder pin) 30 . . . 40 V DC
and Pin 9 of X1
3 between MP 5 (solder pin) 19 . . . 26 V DC
and Pin 15 of X1
4 between MP 5 (solder pin) -20 . . . -27 V DC
and Pin 18 of X1
5 field current supply > 1.5 V AC
between Pin 7 and Pin 8
of X3
6 input voltage between -10 . . . +10 V DC If outside range, input
MP 1 and MP 5 amplifier overranged,
measuring tube
empty or primary head
defective; check acc.
to Sect. 7.5.
7 Short Pin 1, 2 and 3 -10 . . . +10 V DC If outside range,
of X5, measure input signal converter
voltage between defective.
MP 1 and MP 5
If measured
voltages lower,
signal converter
defective,
replace, see Sect. 8.4,
or contact Krohne
Service.
Note: A thermostatic switch is installed in the transformers of the AC versions.
In the DC version, the PCB is equipped with a thermofuse. All signal converters
contain PTR fusible links (typically 100 overload cycles). This allows cyclic
switching on and off of the signal converter under overload conditions.
The cool-down phase may be anything up to one hour.