ESAB Aristo Mig 3001i, Руководство по обслуживанию

Страница: 46 / 76

S0740 800 196/E101019/P76
- 46 -
ca41f2pwr
Checking power board 15AP1
Disconnect the power source from the mains and follow
the instructions below. The numbers of the instructions
refer to the diagrams on this and next page.
1. The thyristor in IC8 is connected in parallel with
resistors R16 and R15.
The resistance must be 24 ohm.
2. Modules IC8 and IC3:
Measure the resistance between collector and gate
of the transistors, it must be higher than 100 kohm.
All transistors must have approximately the same
resistance value.
A faulty transistor is in most cases short-circuited
between collector and gate.
3. Use a multimeter in diode test position. Measure with
the positive and negative of the multimeter
connected as shown in the pictures. The main
transformers must be connected to the circuit board.
The forward voltage drop of the deenergization diode
connected in parallel with the antiparallel diode of
the transistor must be 0.3 to 0.5 V.
4. The NTC resistors that senses the temperature are
connected in a resistance network. When the
temperature of the module is 20
_
C, the resistance
between pins 18 and 19 is about 1.6 kohm.
Depending of the temperature of the module, the
resistance may be in the range of 0.5 to 10 kohm.
The treshold level for overtemperature is 390 ohm.
Both NTC resistors must have the same resistance
value.