Possible Sources Of Problems And How To Deal With Them - Siemens SIMATIC NET S7-1200 Compact Operating Instructions

Maintenance and troubleshooting

5.1 Possible sources of problems and how to deal with them

5.1 Possible sources of problems and how to deal with them
Fuses
Note
The CSM 1277 compact switch module has a resettable fuse / PTC. If the fuse triggers (all LEDs
are off despite correctly applied power supply), the device should be disconnected from the
power supply for approximately 30 minutes before turning it on again.
LED display when voltage is too low
If the power supply is too low, then the internal power supply will switch off causing the DIAG-
LED and all port LEDs to go off. The functionality of the CSM 1277 is no longer available. A supply
voltage of at least 19.2 V is necessary for correct operation.
LED display in case of reverse polarity of the power supply
The CSM 1277 is equipped with reverse polarity protection. A reverse polarity of the supply
voltage does not cause any damage but will not result in any function either. The DIAG‑LED and
all port LEDs are off.
Device defective
If a fault develops, please send the device to your SIEMENS service center for repair. Repairs on-
site are not possible.
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Compact Switch Module CSM 1277
Compact Operating Instructions, 06/2022, A2B00079397-02