Telwin TECNICA 114 Troubleshooting And Repair Manual Download Page 13

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A) Take special note of the procedure for replacing the
IGBT (fig. 4):

fig.2B

ohms

B) Take special note of the procedure for replacing the
secondary diodes (fig. 4):

N.B.

fig. 3

WARNING!

A) Minimum load test:

fig. D

to replace the IGBT undo the screws fastening the
dissipator to the board (

);

remove IGBT Q1 by unsoldering the rheofores and also
remove the solder from the bump contacts on the PCB;

remove the dissipator from the board;

undo the screws holding the IGBT.

Before proceeding with the replacement make sure that the
parts piloting the IGBT are not damaged as well:
-

with the multimeter set on

check the PCB to make

sure there is no short circuit between the 1st and 3rd
bump contacts (between gate and emitter)
corresponding to each component;

alternatively, resistors R8 and R9 could have blown
and/or diodes D8 and D9 may be unable to work at a
correct Zener voltage (this should have been detected in
the preliminary tests);

clean any irregularities or dirt from the dissipator. If the
IGBT module has blown the dissipator may be
irreparably damaged: in such a case it should be
replaced;

apply thermoconductive paste following the general
instructions;

attach the new IGBT to the dissipator with the screw
(torque wrench setting 1 Nm ±20%);

place the dissipator with the new IGBT on the bump
contacts of the PCB, interposing, and attach it with the
screws (torque wrench setting 1 Nm ±20%);

solder the terminals taking care not to let the solder run
along them;

on the solder side cut the protruding part of the
rheofores and make sure they have not shorted
(between the gate and emitter in particular).

undo the screws fastening the dissipator to the board;

remove the secondary diodes by unsoldering the
rheofores and also remove the solder from the bump
contacts on the PCB;

remove the dissipator from the board;

remove the springs locking the diode;

clean any irregularities or dirt from the dissipator. If the
diode has blown the dissipator may have been
irreparably damaged: in such a case it should be
replaced;

apply thermoconductive paste following the general
instructions;

insert the new diode between the dissipator and the
spring, taking care not to damage the component during
assembly (the spring should be inserted by pressure on
the dissipator in order to lock the component);

place the dissipator with the new component on the
bump contacts of the PCB, and attach it with the screws
(torque wrench setting 1 Nm ±20%);

solder the terminals taking care not to let the solder run
along them;

on the soldering side cut the protruding part of the
rheofores and make sure they have not shorted
(between cathode and anode).

make sure that resistor R22 and capacitor C22 of the

snubber are soldered correctly to the PCB (

Tests should be carried out on the assembled machine
before closing it with the top cover. During tests with the
machine in operation never commute the selectors or
activate the ohmic load contactor.

Before proceeding to test the machine, 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 given below are used to verify power source
operation under load.

A) Connect the power source to the static load generator
(code 802110) using cables fitted with the appropriate dinse
connectors.
B) Set up the dual trace oscilloscope. Connect the voltage
probe x100 between the gate of Q1 and the earth to the
emitter, also of Q1. Probe CH2 (x10) to the rheofore of R55
towards C11 and the earth to the anode of D11.
C) Set up a multimeter in DC volt mode and connect the
prods to the OUT+ and OUT- bump contacts.
D) Connect the power supply cable to the main 230Vac
power supply.

during testing prevent contact with the metal

part of the torch because of the presence of high voltages
that are hazardous to the operator.

set up the ohmic load with the switch settings as in the

table in

;

on the front panel turn the current potentiometer to

minimum (turn anti-clockwise as far as it will go);

switch on at the main switch;

start up the ohmic load and make sure that:
-

the waveforms displayed on the oscilloscope

resemble those in

;