-
broken rheophore on one or more capacitor: the
remainder will be overstressed and become damaged by
overheating;
-
ageing after a considerable number of working hours;
-
overheating caused by thermostatic capsule failure.
Probable cause:
-
discontinuation in snubber network;
-
fault in driver circuit;
-
poorly functioning thermal contact between IGBT and
dissipator (e.g. loosened attachment screws: check);
-
excessive overheating related to faulty operation.
Probable cause:
-
excessive overheating related to faulty operation.
Probable cause:
-
discontinuation in snubber network;
-
poorly functioning thermal contact between IGBT and
dissipator (e.g. loosened attachment screws: check);
-
faulty output connection.
Inspect the windings for colour changes. Probable causes:
-
power source connected to a higher voltage than 280Vac;
-
ageing after a substantial number of working hours;
-
excessive overheating related to faulty operation.
It is important to check that all the connections are in good
condition and the connectors are inserted and/or attached
correctly. To do this, take the cables between finger and
thumb (as close as possible to the fastons or connectors) and
pull outwards gently: the cables should not come away from
the fastons or connectors. N.B. If the power cables are not
tight enough this could cause dangerous overheating.
A) With the multimeter set in
mode check the
following components (junction voltages not less than 0.2V):
-
rectifier bridge D1 (
);
-
IGBT's Q1, Q2, Q3, Q4 (absence of short circuits between
collector-gate and between emitter-collector
);
-
secondary board diodes D20, D21, D22, D23 between
anode and cathode (
). The secondary diodes can be
checked without removing the power board: with one prod
on the secondary board dissipator diodes and the other in
sequence on the two power transformer outlets;
-
viper U2 (absence of short circuits between pin 3 - pin 4
and between pin 4 pin 2,
)
B) With the multimeter set in ohm mode check the following
components:
-
resistor R1: 47ohm (pre-charge
);
-
resistors R44, R45: 22ohm (primary snubber
);
-
resistor R20: 10ohm (secondary snubber
);
-
thermostat continuity test on the power transformer: clean
the resin from the bump contacts of ST1 (A,B) and
measure the resistance between the two bump contacts, it
should be approx. 0 ohm (
).
Before proceeding with faultfinding, we should
remind you that during these tests the power source is
powered and therefore the operator is exposed to the danger
of electric shock.
The tests described below can be used to check the operation
of the power and control parts of the power source.
B) Set up the multimeter in DC mode and connect the prods to
the OUT+ and OUT- bump contacts.
C) Position the potentiometer R52 on maximum (turn
clockwise as far as it will go).
D) Connect the power supply cable to a single-phase variac
with variable output 0-300 Vac.
A) Switch on the variac (initially set to the value 0 V), switch off
the main switch on the power source and increase the variac
voltage gradually to 230 Vac and make sure:
- the green power supply LED D12 lights up (
),
- the fan for the power transformer starts up correctly,
- the pre-charge relay K1 commutes (
),
- for voltages close to the rated power supply value (230Vac
±15%) the power source is not in alarm status (yellow LED
D14 off).
if the power source stays in alarm status permanently,
there could be a fault in the control board (in any case,
proceed to make the other tests)
B) Make sure the waveform shown on the oscilloscope
resembles
.
if no signal is present, it may be necessary to replace the
integrated circuit U2 (
).
C) With the multimeter set in
mode make sure that
(
):
-
D) Set up the dual trace oscilloscope. Connect the probe
CH1(x100) to the Q1 collector and probe CH2(x10) to the
IGBT's Q1, Q2, Q3, Q4 fig. 4
Primary diodes D40, D41 fig. 4
Secondary diodes D20, D21, D22, D23 fig. 4
Power transformer and filter reactance (fig. 2A)
6.1 Preparation for testing
6.2 Tests for the TECNICA 150 - 170 - 168GE
(
)
(
)
(
)
4.0 Checking the power and signal wiring
5.0 Electrical measurements with the machine
switched off
6.0 Electrical measurements with the machine in
operation
diode testing
fig. 3
fig. 4
fig. 4
fig. 3 .
fig. 3
fig. 3
fig. 3
fig. 2B
WARNING!
fig. 3
fig. 3
NB.
Fig. A
N.B.
fig. 3
volt
fig. 3
A)
Set up the oscilloscope with the voltage probe x100
connected between pin 3 of U2 and the earth on the anode of
diode D2 (
).
Set up a multimeter in volt mode and make sure that
-
the voltage over the anode of D2 (-) and the cathode of D2
(+) is equal to +13V ±5%;
-
the voltage over the anode of D30 (-) and the cathode of
D7 (+) is equal to +29V ±5%;
-
the voltage over the anode of D31 (-) and the cathode of
D6 (+) is equal to +29V ±5%;
fig. 3
(fig.
3):
- 12 -
FIGURE A
SETTINGS:
PROBE CH1
AMPLITUD IS
-
x100;
- 100V/Div;
- 4 sec/Div.
VERIFICARE CHE:
- FREQUENCY IS
65KHz ±10%;
-
450V ±10%.
µ
TECNICA 150-152-170-168GE
