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Original Message
RE: Sony ST J75 tranny(?) hum
Posted by 6bq5 on August 23, 2023 at 16:17:55:
Itman-
If the hum is present with the unit plugged into mains power, but NOT connected to an antenna, or preamp/system, then it sounds like a mechanical noise coming from the unit.
That being the case, you may be able to tighten the connection of the transformer to the chassis, and check the connection of the chassis parts to each other.
Before you do anything, unplug the unit from the mains power and let it sit for a day or two. This should provide time to allow the components to be deenergized.
Opening the unit carefully, take pictures if this is new for you, making note of orientation of the chassis parts-
once the cover / top is off, the transformer should be readily identifiable - gently try to move it to confirm it is loose.
A Toroidal transformer should have 1 connector thru the middle of the transformer to the bottom of the chassis - check to see that that fastener is tight (righty tighty). If it is an E-I or C Core- the transformer will be square in shape and may have 2-4 fasteners to secure it to the chassis.