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Kevin BowmanAug 2, 2025
What to do if the ST-47 permit lamp comes on but the Scully ST-47 Control Unit ST-47 will not activate an external device?
- MmatthewwoodsAug 2, 2025
If the ST-47 permit lamp illuminates but the ST-47 fails to activate an external device when using the deadman handle, several issues could be the cause. First, turn off the power to the ST-47 using the Bypass switch (if available) or at the power source. Open the front cover and remove the fuse from TB-1. Test the fuse with a multimeter set to Ohms, instead of relying on visual inspection. If replacing the fuse doesn't solve the issue and the fuse continues to blow, inspect the output control wire for shorts. Repair any shorts and replace the fuse with one of the same rating. If the ST-47 still does not permit, there could be a problem with the I.S. Barrier relay. Consult the Scully Service Department.
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