Checking The Semiconductor Module - ESAB Caddyt Arc 150i Service Manual

Checking the semiconductor module

Measuring points for the semiconductor module
Disconnect the machine from the mains and follow the instructions below.
Measurements 2 -- 5: Use a multimeter in diode test position to measure the diodes.
Measure with the positive and negative of the multimeter connected as shown in the picture
above. The main transformer must be connected to terminals T1 and T2.
1. Resistor R31 (and thyristor TY1 in parallel): measure the resistance of R31. It must be
12 ohm (on some boards the resistance of R31 is 6.8 or 10 ohm, which are also
approved values).
2. Diode P1D: measure between resistor R31 and terminal C, pin 1.
Diode P2D: measure between resistor R31 and terminal C, pin 2.
The forward voltage drop must be 0.4 to 0.6 V.
3. Diode N1D: measure between the negative of capacitor 15C1 and terminal C, pin 1.
Diode N2D: measure between the negative of capacitor 15C1 and terminal C, pin 2.
The forward voltage drop must be 0.4 to 0.6 V.
4. Diode D1 connected in parallel with D4: measure between the negative of capacitor
15C1 and terminal T2. The forward voltage drop must be 0.3 to 0.5 V.
5. Diode D2 connected in parallel with D3: measure between the positive of capacitor
15C1 and terminal T2. The forward voltage drop must be 0.3 to 0.5 V.
6. Transistors Q1.1, Q1.2 and Q1.3: measure the resistance between collector, R31, and
gate, pin 15 of the module. The resistance must be higher than 500 kohm.
7. Transistors Q2.1, Q2.2 and Q2.3: measure the resistance between collector, terminal
T2, and gate, pin 10 of the module. The resistance must be higher than 500 kohm.
ct27f6semi
Rectifier diodes and thyristor
IGBT transistors and
freewheel diodes
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S0740 800 161/E061205/P66