Hold the phone
I just fixed this issue.
@ajcrm125 sir your sagely advice was the smoking gun in this.
Reading your post, you mentioned that your problem was the voltage across D6 wasn't high enough to keep D7 from opening up.
I checked my issue, on the common side of D6 and D7 I was reading about 3.5 VDC or something, however, on the +ve side of D6, 0.0v.
I thought that was extremely weird, as I had been through this post earlier, and one of the first things I had checked was that I had continuity between the R29 and D6. low resistance, like, 0.5 ohm across the track but still, a circuit nonetheless.
So I ruled that out as a cause. All the same, I had gone back over, this time with the board powered and this time checked across D6. 0.0v going in.
So I powered everything down and ripped the CPU board out for about the 20th time. I nicked a tiny amount of kynar wire and bridged R29 and D6 on the solder side. Powered up, now higher voltage through D6 this time, (D7 in 3.3v, D6 in 3.9v) and the board is running beautiful, beautiful silence


Spread the word far and wide. This worked for me so if you have had any dramas check that tiny little trace. Through some form of miracle it still reads a circuit but also is not adequate enough to pass voltage. That seems to defy electronics and electrical principles for me, but anyhow it works rock solid.
Problem rating = 0 / 10 bananas, would definitely not try again

