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on the welding side cut away the protruding part of the

rheofores and check they are not shorted (between the
gate and emitter in particular).

The 3 SECONDARY DIODES are attached to the same
dissipator, and when a replacement is required, all of them
should be replaced:
-

undo the screws attaching the dissipator to the board, to

replace diodes D32, D33 and D34;

remove the 3 secondary diodes unsoldering the rheofores

and cleaning any solder from the bump contacts on the
board;

remove the dissipator from the board;

remove the spring locking the 2 diodes;

clean any irregularity or dirt from the dissipator. If the

diodes have burst the dissipator may have been
irreversibly damaged: in this case it should be replaced;

apply thermo-conductive grease following the general

instructions;

insert the new diodes between the dissipator and the

spring, taking care not to damage the component during
assembly (the screw should be inserted under pressure on
the dissipator so as to lock the component);

place the dissipator with the new components in the PCB
bump contacts and fasten them down with the screws
(torque wrench setting for screws 1 Nm ±20%);

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

on the soldering side cut away the protruding part of the
rheofores and check they are not shorted (between
cathode and anode);

make sure resistor R60 and capacitor C32 on the

snubber have been soldered to the PCB correctly (

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
using cables fitted with the appropriate dinse connectors (code
802110).

C) Set up the multimeter in DC mode and connect the prods to
the OUT+ and OUT- bump contacts.
D) Connect the power supply cable to the 230Vac power
supply.

During tests the operator must avoid contact with

the metal parts of the torch because of the presence of
dangerous, high voltage.

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

;

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

;

- the output current is equal to +16Adc

20% and the

output voltage is equal to +13Vdc 20%.

switch off the ohmic load.

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

;

on the front panel turn the current potentiometer to 75A
(approx. half-way);

switch on at the main switch;

start up the ohmic load and make sure that:

the waveforms displayed on the oscilloscope resemble
those in

;

the output current is equal to +75Adc

10% and the

output voltage is equal to +24Vdc 10%.

switch off the ohmic load.

B) Please read the procedure for replacing the secondary
board diodes carefully (fig. 4):

N.B.

fig. 3

WARNING!

A) Minimum load test:

fig. D

Fig. D

B) Intermediate load test:

fig. E

Fig. E

1.1 Preparation for testing

1.2

Scheduled tests for the TECNICA 144

TESTING THE MACHINE

B) Set up the dual trace oscilloscope, connecting probe CH1
(x100) to the collector on Q8 and probe CH2 (x10) to pin 1 on
TP (or the rheofore of R25 towards R2). The earth terminals
are connected together to the emitter, also of Q8.

- 13 -

TECNICA 144 - 164

SETTINGS:
· PROBE CH1 x100
· 100V/Div;
· SONDA CH2 x10;
· 1V/Div;
· 5 sec/Div.

TIME TOLLERANCES
±20%.

· AMPLITUDE CH1

· AMPLITUDE CH2

VERIFY THAT

320V ±10%;

1.2V ±10%.

FIGURE D