Fronius String Control 250/25 DCD DF Instructions De Service page 87

Restoring the
energy supply
manually
(continued) -
If there is no short circuit and the 'PWROK' LED does not light, then the
shutdown is due to under-voltage.
In this case, the DATCOM components require an external energy supply
via an external power supply unit.
In this case, shine a flashlight into the LED and then cover it to
darken it, for example.
When the power supply is reestablished the 'PWROK' LED lights up
green.
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