The top pour in the AUX supply appears to be connected to the cathode of D9, explaining it being live with HVDC.
Off-line power supplies are designed in a way that minimizes the chances of live side circuitry contacting circuitry on the isolated output side, making it dangerously live.
Having everything sharing the same heatsink structure is not safe design practice.
Im not sure what else to say at this stage except to ask, is there a mains earth connection to the isolated output side?
No mains earth connection.
I've checked the heat sink in this setup against every pad on the board and there is no connection. Also isolated all the pads and used plastic standoffs.
Leaving the board as it was designed will mean it will fail 6 months to 1 year from now. 70-80 degrees in standby in open air is a lot. I imagine it will be more than 100 C while operating and in the small confinements of the sub box.
But I understand your concern. I think using plastic standoffs and silicone pads under the heat sink where it meets the board will be enough.
How is signal sent to the box? optical I hope.
How is signal sent to the box? optical I hope.
No, 4 x 3.5mm audio jacks.
Please note that all transistors, diodes and linear regulator are isolated from the heat sink with a ceramic pad. Nothing was electrically connected to the heat sink expect for L11 through those two caps, which I still can't find why.
C19 and C20 would be there for EMI reason, not sure how though. Do they have a voltage rating?
Id prefer then to be proper Y rated safety capacitors.
I removed that connection by isolating the pad to the heat sink, I don't know what's it doing and I wouldn't risk it leaking anywhere with that dangerous common heat sink.
What are your thoughts as to it's purpose?
All the other 3 boards in this units are isolated with silicone pads, so I don't think it's used to move voltage some place else through the heat sink.
I removed that connection by isolating the pad to the heat sink, I don't know what's it doing and I wouldn't risk it leaking anywhere with that dangerous common heat sink.
What are your thoughts as to it's purpose?
All the other 3 boards in this units are isolated with silicone pads, so I don't think it's used to move voltage some place else through the heat sink.
Oh yes, I see that now C19 and C20 should not be a safety issue.
My thoughts about why C19 and C20 were connected to the heat sink? Id say to reduce the electrical noise voltages on the heat sink somehow.
There could not be any good reason for the live hole in the AUX area.