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ELECTRODES



When operating, the electrodes must be kept clean and their

diameter must be kept suitable for the work to be carried out.
Excessively worn electrodes must be replaced.



With water cooled arms, do not use sealing products to

remove water leakage on the electrode taper. To facilitate
electrode removal and to prevent from both taper seizure and
leakage, use high conductivity grease similar to the standard
one.

COOLING CIRCUIT (ON ITEM 7903 ONLY)



Check that cooling water circulates freely and in the required

quantity and that the input temperature is within 10 and 30°C.



Check the status of both water hoses and corresponding

connections.



If the welder is to be stored during the winter in a cold

environment, first carefully drain the cooling circuit to prevent
damage caused by frozen water.

ELECTRICAL CIRCUIT



Periodically check ground efficiency.



Periodically check the mains cable.

EXTRAORDINARY MAINTENANCE

If the welder overheats, check that the duty cycle is not too high
(table 4), the electrode tip diameter is correct (table 2); on water
cooled models check that water flow is adequate.

Item 7903 is equipped with a thermostatic protection which
stops the welder in case of insufficient water. The thermostat
does not protect the transformer against work overloading.

If performances are lower than expected check:



that, when welding, line voltage drop is lower than 15%;



that the supply cables section is adequate;



that the electrodes diameter is appropriate for the work to be

carried out;



on item 7903 that the cooling water flows in the required

quantity;



that the set welding force is adequate for the work in process.

SPARE PARTS

Look at the exploded views and at the spare parts list at the end
of this instruction manual to identify the code of the required
parts. The first number of the code has the following meaning:

1....

standard components widely available from industrial

suppliers (e.g. screws, washers, nuts, etc.).
2....

commercial components which, providing that the

same  quality  parameters  are  adopted,  can  be  purchased
anywhere (hoses, switches etc.).
3....

components manufactured by TECNA

4....

components manufactured by TECNA

5....

electronic circuits and assemblies manufactured by

TECNA.
7....

assemblies composed of parts belonging to any or all

of the above codes but which for the sake of simplicity are
available ready-assembled.

All  spare  parts,  including  standard  or  commercial  ones,  are
available from TECNA. When ordering please always state code
number, and quantity of the spare parts, voltage and frequency,
the  serial  number,  and  year  of  manufacture  of  the  welder.  The
code  number  followed  by  an  asterisk  warns  that  the  part
changes depending on the mains voltage.

REMEDIES FOR WELDS IMPERFECTIONS.

This chapter has been introduced in order to facilitate the troubleshooting of the most common imperfections caused by incorrect
adjustment. Notice that each one can be caused by different causes as there are many parameters affecting the welding process . The
following table specifically refers to low carbon steel spot welding, but, with the due consideration, it can also be useful for other
applications.

FAULT

POSSIBLE CAUSE

POSSIBLE REMEDY

Low welding current.

Increase it.

Low welding time.

Increase it.

Weak welding

Too high electrodes force.

Reduce pressure.

Lacking electrodes maintenance or too high
electrodes diameter.

Clean and line up the electrodes, restore their
dimensions.