Selco Genesis 240 TLH, Repair Manual

Page: 53 / 82

Diagnosis procedure 135
Checks :
With the shunt on the ground cable and a tester set to mVdc, check that the machine delivers the required current.
yes : go on ; no : with a tester set to Vdc, measure between the following cables of Hall probe connector J3:
- n. 34 - n. 36 = + 15 Vdc
- n. 37 - n. 36 = - 15 Vdc
yes : go on ; no :
- check correct insertion of the connector on the Hall probe
- perform power supplies checking procedure
With the machine delivering increasing current values, using a tester set to Vdc, measure between the following
points of board 15.14.254:
CN3/6 - TP3 = -2.7 Vdc
CN3/7 - TP3 = from -100 mVdc approx.
to -2,2 Vdc
(for increasing values set via potentiometer)
yes : go on ; no : replace board 15.14.239
(level 2)
Stage 4 : Machine connected to mains.
Front panel selector set to TIG mode.
Close the master switch.
Set a requirement of 120A via the potentiometer on the front panel and perform lift start by placing the electrode
in contact with the piece and lifting the torch.
Checks :
With oscilloscope set to:
TRIGGER = ROLL
Time scale = 100 ms
Amplitude scale = 2 V
Measure on board 15.14.254 :
TP14 - TP3 = oscillogram no. 6 (shows the moments before and after sparking of the arc)
With oscilloscope set to:
TRIGGER = ROLL
Time scale = 200 ms
Amplitude scale = 500 mV
Measure on board 15.14.254 :
TP11 - TP3 = oscillogram no.7 (shows the moments before and after sparking of the arc)
yes : go on ; no : replace board 14.60.060
Stage 5 : Set front panel selector to MMA.
Set a requirement of 120A via the potentiometer on the front panel.
Spark the arc
Checks :
With oscilloscope set to:
TRIGGER = ROLL
Time scale = 200 ms
Amplitude scale = 2 V
Measure on board 15.14.254 :
TP14 - TP3 = oscillogram no.8 (shows the moments before and after sparking of the arc)
With oscilloscope set to:
TRIGGER = ROLL
Time scale = 200 ms
Amplitude scale = 1 V
Measure on board 15.14.254 :
TP11 - TP3 = oscillogram no.9 (shows the moments before and after sparking of the arc)
yes : go on ; no : replace board 14.60.060