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ERROR CODE 4: THERMAL OVERLOAD
The chain of thermal switches is interrupted. LED1 on A1 comes on. Check connectors, cable
connections and thermal switches for defects. If the unit suffers an early thermal trip, check the
following potential sources of error or fault:
• Fan
• MOSFETs on A9, A13, A10, A14 (parallel circuit, current conduction)
• Diodes AP10, AP11 (parallel circuit, current conduction)
• MOSFETs on A5, A12, A4, A11 (parallel circuits, current conduction)
• Temperature at which the particular thermal switch trips the unit
Signal path: A1 detects contact and signals the fault via A8 to A2.
ERROR CODE 5: COOLING WATER FAULT, GENERAL ERROR INTERRUPT,
OVERVOLTAGE TRIP
Error Code 5 is signalled under certain conditions:
• Cooling water trouble, pressure switch signals a pressure drop; refer to section A6-6 and
"INSTRUCTIONS FOR fault tracing AND REPAIR" - 21 Water Cooling, Adjust Pressure
Contact).
• Failure of supply to A1 and A8, refer to A1-1, A1-2.
• Overvoltage trip of A1 because of excessive output voltage; refer to A1-6 and "Instructions
for Fault Tracing and Repair”- 13 (unit switches off after a short delay).
8 TESTING WITH TESTER IT01
GENERAL DESCRIPTION
The tester IT01 is designed to test the interfaces between control A1, A8 and the power sections
A4, A5, A9, A10, A11, A12, A13, A14 on the DTG405.
The instrument consists of a signal generator that generates +9 V (indicated by the green LED (k))
and –9 V (indicated by the red LED (l)) in an alternating sequence at a frequency of about 1 Hz.
The signal generator is capable of testing the high resistance of the MOSFET gates of all power
transistors installed in the inverter power supply.
The test procedure is described so that tests are conducted without an isolating transformer and
at no load.
Only the tester and mains power are required.
CAUTION! Do not connect the signal generator to the gates when the unit is on since, in this con-
dition, mains voltage is applied to the MOSFET power transistors and the connected IT01.
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