Cebora BRAVO 155 COMB Operating instructions

REPAIR MANUAL
for
BRAVO 155 COMBI
Art.494
20/05/98
M049400g

2
WARNING: All operations listed in this repair manual must be carried out by spe-
cialized, trained personnel.
This manual must be read together with instruction manual 3300627.
When working inside the machine, be especially careful of all wires, non-insulated clamps
and moving parts (motor-driven fan).
DESCRIPTION OF OPERATING LOGIC.
The machine can be started by setting the switch/selector 47 to one of the 7 settings.Power
reaches the following components directly:
1) motor-driven fan 29.
2) control circuit 48.
Now, pressing the torch trigger will close the relay RL1 (located on the circuit 48), thereby
powering the solenoid valve 22 and power transformer 32.The power transformer 32 directly
powers the rectifier 49; the positive (+) and negative (-) poles are connected to a terminal
board located in the coil compartment so that the polarity can easily be reversed if flux-cored
wire is used for welding (no gas).The voltage leaving the rectifier 49 varies in relation to the
setting of the selector switch 47, as listed in the table below:
Open circuit reference voltages for the welding machine:
Selector switch AC Volts DC Volts
setting Measured at the Measured at the
47 rectifier input rectifier output
1 21.3 18
2 23.4 19.8
3 24.4 20.8
4 26.2 22.4
5 29.5 25.4
6 31.1 26.8
7 33.7 29.1
To correctly check the open circuit output voltage from the rectifier 49, you must connect a
1.2-Kohm/10-Watt resistor in parallel to the positive (+) and negative (-) poles, then connect
the Volt meter to the same poles and press the torch trigger (the voltages listed above were
tested at a mains supply voltage of Volts 230 AC).The output voltage from the rectifier is sent
to the circuit 48 (pins n° 1 and 5 of the connector CN1), and is duly managed for use in powe-
ring the gearmotor.This voltage is regulated by the potentiometer on the circuit 48.With this
system, the speed of the gearmotor 8is linked to the position (1-7) of the selector switch 47,
and may later be regulated also by the potentiometer located on the control circuit48.The fol-
lowing are also connected to the same circuit 48:
a) the thermostat 33 (pins n° 2 and 7 of the connector CN1);
b) the torch trigger 45 (pins n° 6 and 8 of the connector CN1);
c) the gearmotor 8(pins n° 3 and 4 of the connector CN1).
To summarize: by pressing the torch trigger 45, the circuit 48 closes the relay RL1.The clo-
sed contact of the relay makes it possible to power the solenoid valve 22, the power tran-
sformer 32 and thus the rectifier 49. The output voltage from the rectifier 49 is used for two
purposes:
a) to power the gearmotor (passing through the circuit 48).
b) As welding voltage (positive and negative poles).
Set the selector switch 47 to "0" to turn off the welding machine.

3
NOTE: the circuit 48 is powered on terminal CN2 for machines with a V 240 AC power sup-
ply, and on terminal CN3 for machines with a V 220 AC power supply.
POSSIBLE ERRORS -TROUBLESHOOTING
Limited current distributed.
Probable causes: Remedies:
1) defective diode or diodes on the rectifier 49. a) replace the rectifier.
2) incorrect connections on the torch 45 or a) check the connections on the torch and
grounding cable 37. grounding cable.
3) defective welding voltage regulator selector a) replace the selector switch.
switch 47.
4) broken connections on the outputs from the a) restore the connection.
power transformer 32.
Excessive metal sprays during welding.
Probable causes: Remedies:
1) welding parameters incorrectly set a) find the appropriate parameters by
adjusting the selector switch 47 and
wire advancement speed potentiome-
ter.
2) welding wire moves forward irregularly a) See paragraph 6.3 of the instruction
manual 3.300.614.
3) grounding cable incorrectly connected a) make sure the connections are correct.
The relais LR1 does not close when the torch trigger is pressed.
Probable causes: Remedies:
1) defective torch trigger 45. a) make sure the trigger and its connec-
tions are in good working order
2) defective circuit 48 a) replace it.
NOTES:
always use original CEBORA spare parts.
After every repair job, all safety tests must be carried out as described in paragraph 6.1.3 of
the standard IEC 974.1.