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Y cap not connected between "quiet nodes"?


Advanced Member level 5
Jun 13, 2021
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Hi Page 7 of the below, shows Y cap connected from Primary "quiet" node to a "quiet node" on the sec , but the sec node is not directly connected to the why didnt they connect the y cap from primary +HV, to secondary centre tap...because the centre tap is not a switching node, (so its suitable "quiet") and is directly connected to the transformer.

Thanks, yes, but that means the connection is via the stray L and R of that 330uF 25V Electrolytic capacitor, plus the stray L of the PCB traces involved.......surely a direct connection of the Y cap would have been better, and could just as easily have been done.
Unclear what you mean by a "quiet" node. Quiet relative to what? No earth connection is indicated on the schematic, so it's somewhat arbitrary.

I would guess that C3 would function approximately the same if it was connected to the other side of the bridge rectifier, or if it connected to the +36V output, or TX center tap. It's likely they tried all combinations and chose this one because it gave a slightly better EMC result overall.
Quiet node meaning not like a switching node, eg not like the drain node.
As you know, Neutral is earthed somewhere so there is effective earthing.

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