Repair of Mordaunt Short Premiere 309W, Active Powered Subwoofer with 8" Aluminium Driver
Fault - Buzzing from Speaker, no output
Removed the active amplifier assembly from the cabinet, on inspection found the cause of the problem to be one of the 4700 uf smoothing capacitors to be faulty, one of the supply voltages was down from 57v to 31v, removed the capacitor after battling with the bonding glue that is applied to everything, the purpose of this is to stop the components shaking around under the extreme Bass conditions.
Replaced the capacitor with a new 4700uf 85 deg component, re-bonded everything including the new capacitor, tested supply voltages with both supply rails at a healthy 57v.
Refitted box cover - not forgetting to seal the speaker cable exit point
Re-fitted amplifier assembly back into the cabinet and cleaned back plate.
Tested unit for 4 hours all ok
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