Why is the Von Duprin PS873 power supply buzzing or chattering?
Some transformers in the power supplies provide a little humming noise and that is normal. If the humming in Von Duprin PS873 power supply is loud follow these steps.
Remove the load from the output of the power supply and see if the humming stops. If it does, You may have grounding or over load issue.
Verify PS873 is putting out 24VDC plus or minus 10%. The buzzing could be caused by the main board putting out excessive voltage. If this is the case you will need to replace the PS873 main board and if not available move to the PS914-XX supply and new option cards.
The potted module at the electrified exit device may be faulty. Check voltage out of potted module on green and yellow. Should measure 0, if holding voltage on yellow indicates pull coil is remaining energized and pulling power supply down, replace the potted module.
If using a battery backup board, overcharged batteries may cause the power supply to chatter. Disconnect the batteries and see if the chattering will stop. If it will, remove AC voltage and connect the batteries and let batteries to operate the hardware for awhile.
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