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• If there are short circuits or faults during
these tests, replace the electronic circuit.
1.4 CHECK OF GENERATOR OPERATION
WITH OSCILLOSCOPE AND VOLTMETER
1. Connect a regulated power supply between
TP1 ( + 15 Vdc) and TP2 (GND), short-circuit
between TP1 and point A (fig. 6); set the
oscilloscope on a time base of 5 uS and a
range of 0.5 V/Div with probe x10 and verify:
• the presence between points: 3 (GND) - 1
15Vdc
GROUND
FIG. 6 - RIF. 1 MOD. CE22541
(probe) (fig. 4) of the waveform shown in fig.
7: if the waveform differs from the one in the
figure or there is no wave form, the electro-
nic circuit is broken.
FIG. 7
M
P
FIG. 8 - RIF. 01 MOD. CE22541
1206
PROFESSIONAL INVERTERS MMA 140-180A
2. Disconnect the feeder and remove the short
circuit, set the oscilloscope with a range of
1V/Div and connect the probe X100 between
points M (GND) and P (Probe) (fig. 8); con-
nect the machine to the power supply, switch
it on:
• the motor fan starts up, and after approx. 2
seconds a wave will appear as in fig. 9.
A
FIG. 9
• check with a voltmeter that the output vol-
tage is approx. 60Vdc (see test specifica-
tion point 2).
• If the wave form does not appear or the
output voltage is not correct, replace the
electronic circuit ref. 1
3. If there is not a correct current regulation
replace the circuit ref. 36; if the fault appears
again, replace the circuit ref. 1
Carry out the final test after the repair.
2.0 FINAL TEST
1. Carry out the safety test according to our ope-
rative instruction N. SLL12, before proceeding
act as follows:
• insert a insulating thickness to avoid dischar-
ges or short circuits between the electronic
boards (ref. 3) and their supporting turrets.
GB
Pag. 5
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