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.
YDEMER ELBISSOP ESUAC ELBISSOP TLUAF
.ti esaercnI .tnerruc gnidlew woL
.ti esaercnI .emit gnidlew woL
.erusserp ecudeR .ecrof sedortcele hgih ooT gnidlew kaeW
hgih oot ro ecnanetniam sedortcele gnikcaL
electrodes diameter.
Clean and line up the electrodes, restore their
dimensions.
.ecrof sedortcele eht esaercnI .tcatnoc seceip ytluaF
.seceip eht naelC .seceip gnoma trid ro tniaP
.gnilooc sedortcele etauqedanI Check the cooling circuit.
sedortcele dna seceip ro tcatnoc seceip ytluaF
faulty contact.
Increase the electrodes force by increasing
pressure.
.ti ecudeR .tnerruc gnidlew hgih ooT netlom fo rettapS
.ti ecudeR .emit gnidlew hgih ooT lairetam
id tsujdA .retemaid sedortcele llams ooT ameter to the value shown on the table.
.erusserp esaercnI .ecrof gnidlew etauqedanI
.ekorts kcehC .seceip eht fo gnipmalc ytluaf sedortcelE
.ti ecudeR .tnerruc gnidlew hgih ooT
.erusserp gnidlew esaercnI .ecrof gnidlew etauqedanI
Burned welds or welds Oxidised pieces to .repap yreme fo snaem yb meht naelC .dlew
showing either craters or
fissures.
Faulty pieces contact or pieces and electrodes
faulty contact.
Increase electrodes force.
.ti tcerroC .pu gninil seceip ytluaF
tseR .snoitamrofed spit sedortcelE ore them to the correct size.
.ti ecudeR .tnerruc gnidlew hgih ooT kcuts seceip kroW
on the electrode Inadequate electrodes diameter. Restore it to the correct dimensions.
rcnI .ecrof gnidlew etauqedanI ease the welding pressure.
Electrodes and connections
reduced life (position 21).
Under-sized electrode in comparison with the
work to be done
Check both size and contact diameter.
Secondary connection
reduced life and oxidation.
Heating caused by an inadequate clamping of the
flexible connection.
Carefully tighten the clamping screws.
gnidlew hgih oot a yb desuac gnitaeh hgih ooT
rate.
Reduce it.
7900 - 7902 / 7902P - 7903 / 7903P
DIRECT.COM
4943 Driscoll Road ¥ Warrensville Heights, OH 44146 USA
www.TECNADirect.com
PAGE 11
844-44-TECNA
DIRECT.COM
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