Repair manual

- repeat this test with the differential probe connected between
resistor R20 (rheofore towards D10) and the earth on the cathode
of diode D11 (check bottom branch).
If the signal is not present and/or the machine is in alarm
status (yellow LED on) the fault could be in the control board (in
which case we recommend replacing it) or in the IGBT driver
circuit ( ).
H) Set up the oscilloscope with the probe x10 connected between
the collector (probe) and emitter (earth) of IGBT 6 on the primary
board ( ).
I) On the primary board reconnect the E ALTO and C BASSO
eyelets of the powertransformer ( ).
J) Keeping the machine in “test mode” switch on the variac
(initially set to 0V), close the main power supply switch on the
machine and gradually increase the voltage generated by the
variac until it reaches 24Vac.Press the torch button and make sure
that:
- the yellow voltage over torch LED, D38, goes off after about 2
seconds;
- the waveform on the displayresembles that in ;
- repeat this test on IGBT 1 of the primary board.
J) Take the variac back down to 0V and also:
- open the main powersupply switchon the machine (OFF);
- open switch SW1 (OFF) on the wiring shown in .
- disconnect the oscilloscope.
If it is very complicated or impossible to repair the boards, replace
them completely. Each board is distinguished by a 6-digit code
(printed in white on the component side after the initials TW).This
code should be used for reference when ordering replacements:
Telwin reserves the right to supply boards that are compatible but
with different codes.Warning: before inserting a new board check
it carefully for damage that may have occurred in transit. We
supply boards that have already been tested and so if the fault is
still present after correct replacement check the other machine
parts Unless the instructions explicitly require it, never adjust the
trimmers on the boards.
- disconnect all the wiring connected to the board and the
cables from the board to the fans and the power transformer.
Never under any circumstances invert the connections
between the primary board and the power transformer when
assemblingthe newboard;
- undo the 4 screws fastening the primary board to the metal
structure;
- undo the 6 screws fastening the dissipator to the metal
structure;
- extract the board upwards from the front panel side (this
movement is simplified by pulling slightly outwards on the front
panel plate).
For assemblyproceed in the reverse order.
Evenif only one IGBT is damaged, all 10 should be replaced.
- after removing the board from the machine undo the 4 nuts
fastening the dissipators (fig.6);
- unsolder the parts, clean the tin from the bump contacts on the
PCB and separate the dissipator from the board;
- before making the replacement make sure that the parts
piloting the IGBT's are not damaged as well:
- with the multimeter on ohms check the PCB to make sure
there is no short circuit between the 1 and 3 bump
contacts (between gate and emitter) corresponding to
each component;
- alternatively resistors R33, R35, R41, R42, R43,
R44, R45, R46, R47, R48 could have burst and/or diodes
D26, D27, D28 and D29 could be unable to operate at a
correct Zener voltage (this should have shown up in the
preliminarytests).
- remove the components (IGBT's, diode bridges or both) by
loosening the screws fastening them to the dissipators;
- clean any irregularities or dirt from the dissipators.If the IGBT's
have burst the dissipators may have been irreversibly
damaged:in such a case they should be replaced;
- apply thermoconductive grease following the general
instructions;
- prepare the components to be replaced. For the IGBT's it is
necessary to bend the rheofores through 90° (never ever bend
or tension the parts of the IGBT's near the case);
- position the component fastening screws, but do not tighten
them up completely;
- join the dissipator/component assembly with the PCB,
inserting all the rheofores in the bump contacts and the
threaded spacers into the 4 fastening holes;
- fasten down the dissipators with the nuts and then tighten up
the components completely in the following order:
- nuts fastening dissipator to PCB with torque wrench setting
2 Nm 20%;
- screws fastening rectifiers to dissipators with torque
wrench setting 2 Nm 20%;
- screws fastening IGBT's to dissipators with torque wrench
setting 1 Nm 20%;
- solder the terminals taking care not to let the tin run along
them;
- on the components side cut the protruding part of the
rheofores and make sure they have not shorted (gate and
emitter in particular).
The 10 IGBT's should belong to the same selection Kit
supplied byTelwin.
N.B.
fig.6
fig.6
fig.3
fig.E
fig.A
N.B.
N.B.
A) Take special note of the procedure for replacing the
IGBT's and/or rectifier bridges:
N.B.
7.0 Repairs,replacing the boards
.
7.1 Removing the primary board (fig. 6)
st rd
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16
SUPERIOR PLASMA 90 HF
FIGURE D
SETTINGS
PROBE CH1 x10;
5 V/Div;
10 sec/Div.
VERIFY THAT:
THE FREQUENCY IS
25KHz 5%;
THE AMPLITUDE ON CH1
IS 10V 10%.
µ
·
·
·
·
±
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±
FIGURE E
SETTINGS
PROBE CH1 x10;
10 V/Div;
VERIFY THAT:
THE FREQUENCY IS
25KHz 5%;
THE AMPLITUDE ON CH1
IS 35V 10%;.
µ
·
·
· 10 sec/Div.
·
±
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±