ESAB Arc 4000i Service Manual page 61

2. Connect an oscilloscope to the SST 2 across terminals GND2 and P2, as shown on
page 60.
Test points for gate pulses from 20AP1
3. Compare the waveform of the gate pulses with the diagram below.
The waveform shape must be as in the diagram.
Pulses from 20AP1 to 15AP2 when the output of 20AP1 is connected to 15AP2.
4. Measure the pulse frequency, it must be 27 kHz ±0.5 kHz.
5. Measure the pulse duration, it must be 41 -- 43 % of the cycle time, measured at --10 V
on the negative pulse, as shown in the diagram above.
6. Measure the maximum pulse voltage, it must be in the range 30 -- 38 V.
The minimum voltage must be in the range from --14 to --16 V.
7. Connect the probe to terminal P1 and the screen to GND1 of the SST 2.
8. Repeat the measurements in item 3 to 6 above.
The pulses on P1 and P2 are in phase with each other.
If the pulse transformer on circuit board 15AP2 is not connected, or if there is a break in the
transformer primary, the pulses will look as shown in the figure below.
Pulses from 20AP1 when the output from 20AP1 is not connected to 15AP2.
cp03f3soft
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S0740 800 191/E080229/P78