Service Manual ALS/XLS 20x/256/27202/2019 | 02 249 RepairTroubleshootingSymptom Diagnosis / possible causeNo machine reaction after switching on;no voltage available.(no fans are running, display and LEDsare dark)After switching the power supply on, only the 5.2 V logic voltage isswitched on. Check if cable A6802 is plugged completely to the 10pin con-nectors at the power supply and on the CPU board. The cableplug engages clearly audible to the connector. Check the logic supply voltage (LED next to the 10pin connec-tor at the power supply).– LED off: The power supply output is overloaded (shorted) or thepower supply is defective. Disconnect cable A6802 from the 10pin connector and switchthe power supply on again.– LED on: logic voltage (5.2 V) available and stable.Settings in the function menu are notstored after switching off.The power fail signal doesn´t arrive at the CPU; when switching themachine off, „Power fail - saving done“ is not displayed. Check cable A6802 and replace, if damaged.Power fail output doesn´t work correctly. Replace power supply.Power fail input at the CPU board doesn´t work correctly. Replace CPU board.24 V and 17/75 V output voltages areswitched off approx. 10 s after switchingon.Rotation speed of the power supply fan is being controlled.If the power supply fan is defective or if the speed control doesn´twork correctly, the outputs 24 V and 17/75 V are switched off ap-prox. 10 s after switching the power supply on (overheat protec-tion). The logic voltage for the CPU board is kept upright.17/75 V output voltages are missing;24 V apply over a short term, but areswitched off approx. 10 s after switchingthe power supply on.Overload on 17/75 V, e. g. by short circuit:Because of the missing supply voltage for the power supply fan,24 V voltage is also switched off (for safety reasons).24 V not available(machine can not initialize correctly, be-cause the external sensors need 24 V).The power supply switches off single outputs, if overload and/orundervoltage occur. Check if cable A6802 is plugged completely to the 10pin con-nectors at the power supply and on the CPU board. The cableplug engages clearly audible to the connector. Check connected loads for short circuit and/or overload.
