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20 CONTINUOUS GAS FLOW
Possible causes:
• Defect on control unit A2
• Defect on control unit A6
• Gas valve defective
• The inverter control A8 signals "Current flowing" to control unit A2. This may be due to a
defect on control unit A8, or a defect in transformer shunt T2.
• Also, transformer shunt T2 may not be supplied with +15 V and -15 V. It only has three con-
nections. If no current is flowing, 0 V ± 30 mV must be applied to the centre connection (out-
put), and +15 V / -15 V to the outer connections.
21 WATER COOLING, ADJUST PRESSURE CONTACT
Integrated with the DTG405 water-cooled unit is a LOW WATER trip F11. This trip does not close
until after a specific water pressure is reached (see section A6-6).
The water pressure is set at the factory and is made by means of a setscrew. See description be-
low:
• The LOW WATER trip is open when the water pump is not running.
• The LOW WATER trip is closed when a short length of connecting hose is used to intercon-
nect the two water connections on the unit and the water pump is running. It is assumed
that, when a torch is connected, a higher pressure will build up.
If the water pressure switch fails to close, Error Code 5 ("Cooling water fault") is displayed on A2.
NOTE! When welding with an air-cooled torch and when electrode welding, the water connections
should be interconnected by a short length of connecting hose, or the cooling connections of a
water-cooled torch should be connected so that the pump is not overloaded.
22 RENEWAL OF CONTROL BOARDS
We advise you only to install control boards which have been factory-adjusted and pre-tested for
a particular unit.
If possible, after replacing a control board, perform the commissioning procedure as described.
23 RENEWING ELECTRONIC MODULE A1
CAUTION! Before carrying out this work, make sure you disconnect the unit from the mains pow-
er supply! In the event of a fault on the unit, the electrolytic capacitors C1 to C4 may still convey
hazardous voltages. Therefore, discharge the capacitors (using a resistor) before renewal!
Place the two insulating sheets supplied with the equipment under A1. The sheets must not show
any signs of damage. The metal sheet contact area must not be damaged either. The contact area
must be flat. Make sure that the surfaces between the sheet and the electronic module as well as
between the sheet and the metal sheet are absolutely clean.
When installation is completed, conduct a high-voltage test at 1875 V (AC) between all the termi-
nals of A1 and the housing. All A1 terminals must be interconnected conductively so that the high
voltage does not damage the circuit on A1.
On the specified connectors, interconnect all the pins via an adapter.
Slowly raise the AC test voltage to the specified level; keep this level for 5 seconds, and then re-
duce to zero. During the test, the current must not exceed 10 mA. Suppression capacitors pro-
duce corrupt readings, so they may be removed for the test (A15, C6, C7).
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